Gio trnh Min dch hc

Mc lc

Chng I: I CNG V MIN DCH HC Chng II: CC C QUAN CA H THNG MIN DCH Chng III: KHNG TH Chng IV: KHNG NGUYN Chng V: CC T BO CH YU CA H THNG MIN DCH Chng VI: B TH Chng VII: CYTOKIN Chng VIII: MIN DCH CHNG VI SINH VT Chng IX: QU MN Chng X: THIU HT MIN DCH Chng XI: TNH T MIN V BNH T MIN Chng XII: CC K THUT MIN DCH THNG DNG

I CNG V MIN DCH HC Tn gi ting Anh immunity (tnh min dch) c ngun gc t ting Latinh immunitas c ngha l min tr s co buc php lut dnh cho cc ngh s quc hi trong thi gian ng chc. Trong lch s, min dch c dng ch s khng mc bnh, m c th l cc bnh nhim trng. Trong c th, tt c cc t bo v phn t ho hc chu trch nhim v tnh min dch hp thnh h thng min dch, v ton b nhng p ng ca chng to ra i vi nhng cht l xm nhp vo c th c gi l p ng min dch. Chc nng sinh l ca h thng min dch l bo v mt c th chng li cc vi sinh vt gy bnh xm nhp vo c th . Tuy nhin, nhng cht l khng gy bnh xm nhp vo c th cng gy ra p ng min dch. Hn na, c ch bo v bnh thng cn c khi gy ra mt s thng tn cho c th. Do , ngi ta a ra mt nh ngha bao hm hn i vi tnh min dch l phn ng i vi cc cht l, bao gm c vi khun v cc i phn t nh protein, cc polysaccharide, khng k phn ng l sinh l hay bnh l. Min dch hc l mn hc nghin cu tnh min dch vi ngha rng ny i vi cc hot ng phn t v t bo xy ra sau khi cc vi sinh vt v i phn

t xm nhp vo c th. Cc nh s hc k rng: Thucydides, mt ngi Hy Lp Athens, l ngi u tin vo th k th V trc Cng nguyn cp n tnh min dch chng li bnh nhim trng m lc c gi l bnh dch. Khi nim tnh min dch c l tn ti rt lu trc Trung Quc v ngi dn y c tp tc cho ngi dn ht cht bt lm t da ca ngi b u ma khi phng nga bnh ny. Cn min dch hc, vi t cch l mt mn hc hin i, li l mt ngnh khoa hc thc nghim, trong cc hin tng min dch c gii thch da trn nhng quan st thc nghim. Min dch hc, vi t cch l mt mn hc thc nghim, tin ho theo nng lc ca con ngi hiu bit v kim sot chc nng ca h thng min dch. Bng chng u tin trong lch s v nng lc ny l thnh cng ca Edward Jenner trong vic chng nga phng bnh u ma. Jenner l mt thy thuc ngi Anh, ng quan st thy rng nhng ngi vt sa b bnh u b v sau hi phc th khng bao gi mc bnh u ma na. Da vo nhn nh ny, ng ly dch t vt thng ca ngi b u b tim cho mt a tr 8 tui. a tr ny sau cho tip xc trc tip vi ngi bnh u ma th khng mc bnh v ng gi cch bo v ca mnh l "vaccination (chng nga) (ch vaccination bt ngun t ting Latinh vacca ngha l con b ci) v cho xut bn quyn sch Vaccination vo nm 1798. T bin php phng bnh nhim trng ny pht trin rng ri v cho n nay n vn l phng php phng nga hiu qu nht i vi cc bnh nhim trng (Bng 1.1). Mt vn bn c ngha quan trng i vi ngnh Min dch hc l cng b ca T chc Y t Th gii nm 1980 rng bnh u ma l cn bnh u tin trn th gii b loi tr nh vo cng tc chng nga. T nhng nm 1960, chng ta c mt s chuyn bin trong hiu bit v h thng min dch v chc nng ca n. Cc tin b v k thut nui cy t bo (k c k thut sn xut khng th n dng), ho min dch, phng php DNA ti t hp, ng vt bin i gen, ... chuyn min dch hc t ch ch yu l cc hot ng m t thnh mt ngnh khoa hc m trong cc hin tng min dch c gii thch bng nhng thut ng sinh ho v cu trc. Trong chng ny chng ti trnh by nhng c im chung ca p ng min dch cng nh gii thiu nhng khi nim to nn nhng bc ngoc trong ngnh min dch hc hin i.

Bng 1.1. Hiu qu ca vc-xin i vi mt s bnh nhim trng thng gp ti Hoa K

Bnh Bch hu Si Quai b Ho g Bi lit Rubella Un vn H. Znfluenza typ B Vim gan B

S bnh S bnh nhn nm nhn nm 2000 2000 206.939 2 (1921) 894.134 63 (1941) 152.209 315 (1968) 265.269 6.755 (1934) 21.269 0 (1952) 57.686 152 (1969) 1.560 (1923) 26 ~20.000 1.212 (1984) 26.611 6.646 (1985)

T l phn trm -99,99 -99,99 -99,99 -97,73 -100,00 -99,84 -98,44 -93,14 -75,03

1.1. Tnh min dch bm sinh v thu c S khng chng li vi sinh vt trong c th ban u l nhng phn ng ca h thng min dch bm sinh v sau l ca min dch thu c (Hnh 1.1, Bng 1.2). H min dch bm sinh (cn gi l min dch t nhin) bao gm cc c ch khng tn ti trong c th khi cha c nhim trng v sn sng p ng rt nhanh khi vi sinh vt xm nhp. Cc c ch ny ch yu phn ng chng li vi sinh vt ch khng phn ng vi cc vt l khng phi l vi sinh vt; ng thi chng phn ng theo mt c ch ging ht nhau khi vi sinh vt xm nhp ti i ti li. Cc thnh phn chnh ca min dch bm sinh bao gm: (1) cc hng ro vt l v ho hc nh da, nim mc, cc cht khng khun c tit ra trn cc b mt ny; (2) cc t bo thc bo

(t bo trung tnh, i thc bo) v t bo NK (t bo git t nhin); (3) cc protein trong mu, bao gm cc thnh phn ca h thng b th v cc cht trung gian khc ca phn ng vim; v (4) cc protein gi l cytokin c vai tr iu ho v phi hp cc hot ng ca t bo trong h min dch bm sinh. C ch hot ng ca h min dch bm sinh ch c hiu cho nhng cu trc chung ca tng nhm vi sinh vt v khng c hiu cho nhng khc bit tinh t trong tng nhm ny. H min dch bm sinh to ra nhng phn ng u tin chng li s xm nhp ca vi sinh vt. Ngc vi h min dch bm sinh, c nhng p ng min dch khc c kch thch bi s tip xc vi vi sinh vt v to ra cng tng dn nu s tip xc ny c lp i lp li. Bi v dng p ng ny ch xut hin sau khi vi sinh vt xm nhp c th nn n c gi l min dch thu c. Tnh cht c bit ca p ng min dch thu c l tnh c hiu i vi tng phn t v kh nng nh khi phn t xm nhp tr li c th to ra mt p ng mnh hn nhiu so vi ln xm nhp u tin. H min dch thu c c kh nng nhn din v phn ng li vi nhiu vt l c bn cht nhim trng hoc khng nhim trng. Ngoi ra, n cn c kh nng tuyt vi trong vic phn bit s khc nhau rt nh gia cc vt l ny v v vy m n cn c gi l min dch c hiu. Cc thnh phn ca min dch thu c l t bo lymph v cc sn phm ca chng. Nhng cht l to ra p ng min dch c hiu hoc chu tc ng ca h min dch ny c gi l khng nguyn. Theo thi quen, cc thut ng p ng min dch v h thng min dch thng dng cho p ng min dch thu c, tr khi c nhng nhn mnh ring khc n min dch bm sinh.

Hnh 1.1. Min dch bm sinh v thu c Cc c ch ca min dch t nhin cung cp sc khng ban u i vi nhim trng. p ng min dch thu c n mun hn vi s hot ho t bo lymph. Mc mnh hay yu ca p ng min dch bm sinh v thu c ph thuc tng loi nhim trng.

Bng 1.2. c im ca min dch bm sinh v min dch thu c

c im Tnh c hiu Tnh a dng Tnh nh Tnh khng p ng vi bn thn

Bm sinh i vi cu to chung ca nhm vi sinh vt t Khng C

Thu c i vi khng nguyn c hoc khng nhim trng Rt nhiu C C

Cc thnh phn tham gia Hng ro l ho Da, nim mc, T bo lymph cc ho cht nim mc; khng khng khun th nim mc Cc protein mu B th Khng th T bo Thc bo, t bo T bo lymph NK Cc thnh phn ca p ng min dch bm sinh v thu c thng xen ln vi nhau trong mt c ch khng chung ca c th thng qua nhiu loi t bo v phn t. Ring min dch bm sinh c th gip c th thot khi s tn cng ca mt s vi sinh vt, nhng nhiu vi sinh vt gy bnh c kh nng vt qua hng ro min dch ny nn s loi tr chng cn n mt c ch khng mnh hn nhiu, l min dch thu c. C hai mi lin kt quan trng gia min dch bm sinh v thu c. Th nht, min dch bm sinh c kh nng kch thch p ng min dch thu c v nh hng n bn cht ca min dch thu c. p ng ca min dch thu c c s dng nhiu c ch hiu qu ca min dch bm sinh loi tr vi sinh vt v c kh nng tng cng hot ng khng khun ca min dch thu c. Min dch bm sinh v mt di truyn thuc h thng khng c nht ca c th ch, cn min dch thu c th mi c c nh tin ho v sau. ng vt c xng sng, sc khng ca c th ch chng li vi sinh c th ch yu c m trch bi min dch bm sinh, bao gm cc thc bo, v cc phn t protein lu ng trong mu. Min dch thu c bao gm t bo lymph v khng th, xut hin u tin loi xng sng c hm v cng bit ho i vi cc loi tin ho v sau. 1.2. Cc kiu p ng min dch thu c C hai kiu p ng min dch thu c, l p ng th dch v p ng qua trung gian t bo. C hai kiu ny u c s tham gia ca rt nhiu thnh phn ca h thng min dch vi mc ch l loi tr nhiu loi vi sinh vt khc nhau ra khi c th (Hnh 1.2). Min dch dch th c thc hin qua trung gian ca nhng phn t hin din trong mu v dch nim mc c tn l khng th, c sn xut bi t bo lymph B (cn gi l t bo B). Khng th c kh nng nhn din khng nguyn vi sinh vt, trung ho tnh gy bnh v tc ng ln vi sinh vt loi tr n qua nhiu c ch hiu qu khc nhau. Min dch dch th l c ch khng ch yu chng li cc vi sinh vt ngoi bo

cng nh c t ca chng theo c ch khng th lin kt vi cc vi sinh vt hoc c t xc tin vic loi tr. Bn thn khng th l nhng phn t c chuyn mn ho, nhng tup khng th khc nhau c th to ra nhiu c ch loi b khng nguyn khc nhau. Mt s tup khng th c kh nng xc tin hot ng thc bo, mt s khc li kch thch t bo bch cu sn xut ra cc cht trung gian ca phn ng vim. Min dch qua trung gian t bo (cn gi l min dch t bo) l kiu p ng c thc hin qua trung gian ca t bo lymph T (cn gi l t bo T). Cc vi sinh vt ni bo nh virus v mt s vi khun c kh nng sng v nhn ln trong i thc bo cng nh mt s t bo ch khc, v th chng khng chu tc ng trc tip ca khng th lu ng trong mu. S khng chng li nhng vi sinh vt kiu ny l chc nng ca min dch t bo.

Hnh 1.2. Cc kiu min dch thu c Trong min dch dch th, t bo B tit ra khng th ngn chn nhim trng v loi b cc vi khun ngoi bo. Trong min dch qua trung gian t bo, t bo T hot ha i thc bo tiu dit vi khun b n vo bn trong t bo ny hoc t bo T gy c trc tip tiu dit t bo b nhim khun.

Min dch bo v chng li mt vi sinh vt c th c to ra nh kch thch ca vi sinh vt hoc nh truyn khng th hoc t bo lymph c hiu t bn ngoi vo (Hnh 1.3). Cch thc to khng th qua kch thch trc tip vi vt l c gi l min dch ch ng v c th tip xc vi vt l ng vai tr ch ng trong vic p ng vi khng nguyn. Nhng c th hoc t bo lymph cha tng c tip xc vi mt khng nguyn no c gi l nguyn vn hay nguyn (naive). Cn nhng c th c tip xc vi mt khng nguyn vi sinh vt no ri v sau c bo v chng li nhng ln tip xc khc c gi l min nhim (immune).

Hnh 1.3. Min dch ch ng v th ng Min dch ch ng c to ra khi c th ch tip xc vi vi sinh vt hoc khng nguyn vi sinh vt, trong khi min dch th ng c vay mn nh truyn khng th hay t bo lymph T c hiu. C hai loi u to ra sc khng i vi vi sinh vt nhng ch c min dch ch ng l c tnh nh min dch.

Ngi ta cng c th mang tnh min dch n cho mt c th bng cch truyn huyt thanh hoc t bo lymph t mt c th khc c gy min dch. Cch lm ny c gi l truyn min dch th ng, thng hay thc hin trn ng vt th nghim. C th nhn sau s c tnh min dch chng li khng nguyn tng ng mc d cha ln no tip xc vi khng nguyn ny. Do kiu min dch ny c gi l min dch th ng. Gy min dch th ng l mt phng php hu ch cung cp sc khng nhanh, khng phi ch cho n khi min dch ch ng xut hin. Mt v d ca min dch th ng l truyn khng th t m sang con trong thi k bo thai gip cho a tr chng li nhim trng trong thi k ch i min dch ch ng ca tr hnh thnh. Ngi ta cng dng phng php min dch th ng chng li c t vi khun gy cht ngi (v d c t un vn) bng cch truyn khng th t con vt c gy min dch bi vi sinh vt . K thut truyn min dch th ng (hay cn gi l to min dch vay mn) cng

c th thc hin vi nhng t bo v phn t khc nhau min l chng c nng lc min dch c hiu. Tht ra, thut ng min dch dch th (humoral immunity) ban u c nh ngha nh mt kiu min dch c th truyn c sang cho con vt cha nhim bng cht dch trong mu c cha khng th v khng c t bo (tc l huyt thanh hoc huyt tng m t c gi l th dch - humor). Cng vy, min dch qua trung gian t bo (cell-mediated immunity) c nh ngha l mt dng min dch c th truyn sang cho c th cha nhim di dng t bo (lymph T) ch khng phi dch th. Nm 1890, Emil von Behring v Shibasaburo Kitasato trnh din th nghim u tin v min dch dch th. H cho thy rng, nu huyt thanh ca con vt khi bnh bch hu c truyn cho con vt cha nhim th con vt ny s c kh nng khng c hiu i vi bnh bch hu. Thnh phn hiu lc trong huyt thanh lc c gi l khng c t v n trung ho tc dng bnh l ca c t bch hu. u nhng nm 1890, Karl Landsteiner v cc nh nghin cu khc chng minh rng khng phi ch c c t m nhng cht khng c ngun gc vi sinh vt khc cng c th to ra p ng min dch dch th. T cc th nghim , ngi ta a ra mt thut ng mi l khng th (antibody) ch thnh phn protein huyt thanh to ra tnh min dch dch th. Nhng cht lin kt vi khng th v to ra s sn xut khng th c gi l khng nguyn (antigen). Nm 1900, Paul Ehrlich a ra mt l thuyt mi v tnh c hiu ca phn ng khng nguyn khng th, m nhng bng chng thc nghim cho l thuyt ny ln lt c a ra trong sut 50 nm k t khi c pht hin ca Lansteiner. L thuyt ca Ehrlich v s khp nhau v mt l ho ca khng nguyn v khng th rt c gi tr vo thi k u ca min dch hc. S nhn mnh v khng th trong l thuyt ny dn n s tha nhn chung tm quan trng ca min dch dch th, min dch c trung gian bi nhng cht hin din trong cc dch c th. L thuyt t bo v min dch c Metchnikoff a ra. Trnh din ca ng v s thc bo xy ra xung quanh chic gai hng c m vo c th trong sut ca u trng sao bin c xut bn nm 1893. y c l l bng chng thc nghim u tin v vai tr p ng t bo i vi vt l xm nhp vo c th. Cc quan st ca Sir Almroth Wright vo u nhng nm 1900 cho thy rng, trong huyt thanh min dch c nhng yu t thc y s thc bo vi khun bng cch bc xung quanh vi khun, iu ny lm ngi ta tin rng khng th chun b vi khun thc bo d bt gi hn, qu trnh ny c gi l opsonin ho. Nhng ngi theo trng phi t bo ny khng chng minh c rng tnh c hiu ca min dch i vi vi sinh vt cng th hin c qua min dch t bo. L thuyt t bo trong min dch

c khng nh vo nhng nm 1950, khi George Mackaness chng t rng, s khng i vi mt loi vi sinh vt ni bo, con Listeria monocytogenes, c th vay mn bng cch truyn t bo ch khng phi truyn huyt thanh. Chng ta bit rng tnh c hiu ca min dch t bo l do lymph, t bo ny c chc nng lm nhc trng iu khin cc t bo khc nh i thc bo nhm loi b vi sinh vt. Trn lm sng, tnh min dch i vi mt vi sinh vt b nhim trc y c th o c mt cch gin tip bng cch nh lng cc sn phm ca min dch hin din trong c th (v d khng th c hiu trong huyt thanh) hoc chit xut cc cht t c th vi sinh vt v nh gi phn ng ca c th i vi cc cht ny. Mt phn ng ca c th i vi mt khng nguyn vi sinh vt no ch xy ra nu trc c th tip xc vi khng nguyn ny ri; khi c th c gi l c mn cm i vi khng nguyn . Ngi ta cho rng cc c th c mn cm c kh nng to ra p ng min dch bo v i vi vi sinh vt . 1.3. Cc c im chnh ca p ng min dch thu c Tt c p ng dch th v t bo i vi vt l c nhiu tnh cht c bn phn nh tnh cht ca t bo lymph lm trung gian cho phn ng ny (Bng 1.3).

Bng 1.3. Cc c im chnh ca p ng min dch thu c

c im c hiu a dng Nh Chuyn mn ho T gii hn

ngha chc nng m bo cc khng nguyn khc nhau to ra p ng c hiu ring cho chng Cho php h thng min dch p ng c nhiu loi khng nguyn Dn n p ng mnh hn i vi khng nguyn tng tip xc To ra p ng ti u chng li nhiu loi vi sinh vt khc nhau Cho php h thng min dch p ng c vi cc khng nguyn mi xm

Khng phn ng vi bn thn

nhp Ngn nga cc tn thng i vi c th ch trong sut qu trnh phn ng vi khng nguyn l

1.3.1. Tnh c hiu v a dng p ng min dch c hiu cho tng khng nguyn khc nhau v c ngay cho tng thnh phn cu trc ca khng nguyn nh protein, polysaccharide hoc i phn t (Hnh 1.4). Nhng thnh phn ny ca khng nguyn c gi l quyt nh khng nguyn hay epitop. Tnh c hiu ny c c l nh trn mng ca cc t bo lymph ring l c nhng th th ring nhn din nhng cu trc khng nguyn khc nhau. Trong c th c gy min dch c nhiu cln t bo lymph vi tnh c hiu khc nhau tn ti, chng c th nhn din v p ng li tt c khng nguyn ngoi lai. Khi nim ny l nn tng ca l thuyt chn cln m chng ta s cp n v sau ny.

Hnh 1.4. Tnh c hiu, nh, v t gii hn ca p ng min dch Khng nguyn X v Y to ra s sn xut cc khng th khc nhau (tnh c hiu). p ng ln th hai i vi khng nguyn X th nhanh hn v mnh hn (nh). Mc khng th gim dn theo thi gian sau mi ln gy min dch (t gii hn). Ngi ta cng thy c hin tng tng t th ny i vi min dch t bo. Tng s tnh c hiu ca t bo lymph trong mt c th l mt con s cc k ln v c gi l kho lymph (lymphocyte repertoire). Ngi ta c tnh rng h thng min dch ca mt c th c th phn bit t 107 n 109 quyt nh khng nguyn khc nhau. iu ny to nn tnh a dng ca kho lymph. Mt h qu c th thy l cc din kt hp khng nguyn ca khng th v th th khng nguyn trn t bo lymph cng c cu trc rt a dng tng ng vi kho lymph ny. 1.3.2. Nh min dch S tip xc ca h min dch vi khng nguyn l lm tng cng p ng vi khng nguyn khi n xm nhp c th cc ln sau. p ng cc ln lp li v sau i vi mt khng nguyn c gi l p ng min dch th cp. p ng ny thng nhanh hn, mnh hn v khc v cht so vi p ng s cp khi c th tip xc khng nguyn ln u tin (xem Hnh 1.4). Nh min dch c c mt phn l do c mi ln tip xc vi c th th khng nguyn m rng cln lymph c hiu cho khng nguyn . ng thi, s kch thch t bo lymph nguyn vn ca khng nguyn to ra cc t bo nh tn ti lu di. T bo nh c tnh cht c bit lm cho chng loi b khng nguyn hiu qu hn so vi t bo lymph nguyn vn. V d, t bo lymph B nh sn xut khng th lin kt vi khng nguyn vi i lc mnh hn so vi t bo B cha tng tip xc vi khng nguyn . T bo T nh cng c kh nng tr v ni nhim trng nhanh hn t bo T nguyn vn (tc cha tng tip xc khng nguyn). 1.3.3. Chuyn mn ho H thng min dch p ng mt cch c bit v khc nhau i vi tng vi sinh vt sao cho c th to hiu qu ti a cho c ch khng. Nh vy, min dch dch th v min dch t bo c hnh thnh mt cch khc nhau di s kch thch ca nhng loi vi sinh vt khc nhau hoc cc giai on nhim trng khc nhau (ngoi bo v ni bo) ca mt vi sinh vt bo v c th ch chng li loi vi sinh vt vo giai on nhim trng . V ngay trong tng

kiu min dch dch th hay t bo th bn cht ca khng th hay t bo T c to ra cng khc nhau tuy loi vi sinh vt kch thch. 1.3.4. T gii hn Tt c p ng min dch bnh thng s phai nht dn theo thi gian tr li h min dch trng thi ngh ban u, tnh trng ny gi l hng nh ni mi (homeostasis). Tnh trng cn bng dch th c duy tr ch yu l v p ng min dch c khi ng bi khng nguyn v nhm n loi tr khng nguyn, v nh vy tc l loi tr nguyn nhn gy hot ho t bo lymph. Ngoi ra, khng nguyn v p ng min dch cn kch thch c ch iu ho nhm c ch chnh p ng ny. 1.3.5. Khng phn ng vi bn thn Mt trong nhng tnh cht quan trng ca h min dch ca ngi bnh thng l kh nng nhn bit, p ng v loi b khng nguyn l (khng phi ca bn thn) v khng phn ng li gy hi cho c th (bn thn). Tnh cht khng p ng min dch ny cn c gi l dung np. Dung np i vi khng nguyn bn thn, tc t dung np, c duy tr bi nhiu c ch. Nhng c ch ny bao gm loi b t bo lymph c mang th th c hiu cho khng nguyn bn thn v cho php t bo lymph tiu dit cc khng nguyn t thn c kh nng to ra phn ng chng li bn thn. Nhng bt thng v kh nng t dung np c th dn n p ng min dch i vi khng nguyn bn thn (t khng nguyn) v hnh thnh cc bnh t min. Cc tnh cht trn y ca min dch thu c rt cn thit duy tr chc nng khng bnh thng ca c th ch.

1.4. Cc thnh phn t bo ca h thng min dch thu c Cc t bo chnh ca h min dch l t bo lymph, t bo trnh din khng nguyn, v t bo hiu qu. T bo lymph l nhng t bo c kh nng nhn din mt cch c hiu khng nguyn l v to phn ng chng li chng. Do vy, lymph bo l t bo trung gian ca c min dch dch th

v min dch t bo. C nhiu tiu qun th t bo lymph khc nhau v c cch nhn din khng nguyn ln chc nng ca chng (Hnh 1.5). T bo lymph B l t bo duy nht c th sn xut khng th. Chng nhn din khng nguyn ngoi bo (k c khng nguyn trn b mt t bo) v bit ho thnh t bo tit khng th, do chng tc dng nh t bo trung gian ca min dch dch th. T bo lymph T nhn din khng nguyn ca vi sinh vt ni bo v c chc nng tiu dit nhng vi sinh vt ny hoc nhng t bo b nhim trng. Th th khng nguyn ca chng l nhng phn t mng khc vi khng th nhng c cu trc lin quan. T bo T c tnh c hiu rt cht ch i vi khng nguyn. Chng ch nhn din nhng phn t peptid gn vi mt protein bn thn c m ho bi nhng gen trong phc h ha hp m ch yu (MHC) v c th hin trn b mt ca nhng t bo khc. Nh vy, t bo T nhn din v phn ng vi khng nguyn gn trn b mt t bo ch khng phi khng nguyn ho tan. T bo T c nhiu nhm mang chc nng khc nhau. c bit nhiu nht l t bo T gip , T gy c. Khi p ng vi khng nguyn, t bo T gip tit ra nhng protein gi l cytokin c chc nng kch thch s tng sinh v bit ho ca t bo T v mt s t bo trong c t bo B, i thc bo v cc bch cu khc. T bo T gy c git cc t bo sn xut ra khng nguyn l nh cc t bo b nhim virus hay nhng vi khun ni bo khc. Mt s t bo T c gi l T iu ho c chc nng c ch p ng min dch. Bn cht v vai tr sinh l ca t bo T iu ho cha c bit y . C mt nhm t bo lymph th ba l t bo git (NK), y l nhng t bo tham gia vo h thng min dch bm sinh chng li nhim trng virus v cc vi sinh vt ni bo khc. S khi ng v pht trin p ng min dch thu c bao gi cng i hi khng nguyn phi c bt gi v trnh din cho t bo lymph. T bo chu trch nhim lm vic ny c gi l t bo trnh din khng nguyn (APC). T bo trnh din khng nguyn c chuyn mn ho cao nht l t bo hnh sao (dendritic), chng bt gi nhng vi sinh vt t bn ngoi xm nhp vo, vn chuyn nhng khng nguyn ny n cc c quan lymph v trnh din khng nguyn cho nhng t bo T khi ng p ng min dch. S hot ho t bo lymph bi khng nguyn dn n s hnh thnh nhiu c ch loi b khng nguyn. S loi b khng nguyn i hi s tham gia ca nhng t bo gi l t bo hiu qu. T bo lymph hot ho, thc bo n nhn, v mt s bch cu khc c th lm chc nng t bo hiu qu trong nhng p ng min dch khc nhau.

T bo lymph v nhng t bo h tr ca h min dch c tp trung ti cc c quan lymph; chng tng tc vi nhau to ra p ng min dch. T bo lymph cng hin din trong mu. T mu chng c th theo mu tun hon n cc m lymph v cc v tr ngoi bin ni khng nguyn thng xm nhp loi tr chng.

1.5. Cc giai on ca p ng min dch thu c Qu trnh p ng min dch thu c c th chia thnh nhiu giai on

khc nhau: nhn din khng nguyn, hot ho t bo lymph, v giai on hiu qu (loi tr khng nguyn). Sau l s tr li hng nh ni mi v duy tr tnh nh min dch (Hnh 1.6). Tt c p ng min dch u c khi u bng nhn din khng nguyn c hiu. S nhn din ny dn n hot ho t bo lymph v sau l hnh thnh cc c ch hiu qu lm chc nng loi b khng nguyn. Sau khi khng nguyn c loi b, p ng min dch du i v tr li tnh trng hng nh ni mi.

Hnh 1.6. Cc giai on ca p ng min dch thu c Ba giai on u c tn l nhn din khng nguyn, hot ho t bo lymph v hiu qu (loi b khng nguyn). p ng tt dn v cc t bo lymph c khng nguyn kch thch s cht dn do hin tng cht lp trnh (apoptosis), nhng t bo c hiu khng nguyn cn li l t bo nh. Thi gian ca mi giai on thay i tu theo bi cnh p ng. Trc y tng trng cho cng ca p ng. M hnh ny p dng cho c min dch dch th v min dch t bo.

1.5.1. Nhn din khng nguyn

Mi c th s hu mt lng t bo lymph vi rt nhiu cln khc nhau. Mi cln mang sn nhng yu t nhn din v p ng vi mt quyt nh khng nguyn nht nh. Khi khng nguyn xm nhp c th n tm n cln lymph tng ng v hot ho n (Hnh 1.7). Quan nim c bn ny c gi l thuyt chn cln (clonal selection hypothesis), ln u tin c Niels Jerne a ra vo nm 1955 v c Macfarlane Burnet lm sng t vo nm 1957. y l gi thuyt gii thch ti sao h thng min dch li c th p ng vi mt s lng rt ln cc loi khng nguyn khc nhau. Theo gi thuyt ny, cc cln lymph c hiu khng nguyn c sn trong c th trc khi tip xc vi khng nguyn. Nhng t bo trong cng cln mang th th khng nguyn ging ht nhau v khc vi t bo ca cln khc. Mc d rt kh xc nh gii hn trn ca s lng quyt nh khng nguyn m h min dch ca mt c th ng vt c v c th nhn din c, nhng ngi ta thng cho rng con s ny l vo khong t 107 n 109. y l con s c lng hp l i vi s lng protein th th khng nguyn c sn xut v do ngi ta cho rng s lng cln t bo lymph hin din trong c th cng nh th. Khng nguyn l s tng tc vi cln t bo lymph c hiu cho khng nguyn tn ti sn trong m lymph to ra p ng min dch.

Hnh 1.7. Thuyt chn cln Mi khng nguyn (x hoc y) chn mt cln lymph c hiu c sn v kch thch s tng sinh, bit ho ca cln . S ny ch trnh by qu trnh lymph B pht trin thnh t bo hiu qu v tit ra khng th, nhng nguyn l ny cng p dng cho c t bo T.

Nhng nguyn l c bn ca thuyt chn cln dn c chng minh mt cch thuyt phc qua nhiu th nghim v to nn nn tng cho quan nim hin nay v s nhn din khng nguyn ca t bo lymph c hiu.

1.5.2. Hot ho t bo lymph S hot ho t bo lymph i hi 2 tn hiu khc nhau: tn hiu th nht l khng nguyn v tn hiu th hai l cc sn phm vi sinh vt hoc l cc thnh phn ca p ng min dch bm sinh i vi vi sinh vt (Hnh 1.8). tng ny c gi l thuyt hai tn hiu i vi s hot ho lymph bo. Yu cu v khng nguyn (tc tn hiu 1) nhm m bo tnh c hiu ca p ng min dch. Cn yu cu v kch thch ph do sn phm vi khun hoc ca p ng bm sinh i vi vi khun nhm m bo phn ng ch c to ra khi cn thit (tc chng vi khun hoc cht c hi khc) ch khng chng li cc cht v hi bao gm khng nguyn bn thn.

Hnh 1.8. Yu cu hai tn hiu i vi hot ho lymph bo S nhn din khng nguyn ca lymph bo cung cp tn hiu 1 cho s

hot ho, v cc thnh phn ca vi sinh vt hoc cc cht to ra trong qu trnh p ng min dch bm sinh cung cp tn hiu 2. Trong hnh ny, t bo lymph l t bo B, nhng i vi t bo T cng c nguyn l nh vy p ng ca lymph bo i vi khng nguyn v tn hiu th hai bao gm s tng hp cc protein mi, tng sinh t bo, v bit ho thnh t bo hiu qu v t bo nh. 1.5.3. Giai on hiu qu ca p ng min dch: loi b khng nguyn Trong sut giai on hiu qu ca p ng min dch, cc lymph bo c khng nguyn hot ho s to ra nhng chc nng hiu qu tin n vic loi b khng nguyn. Khng th loi b khng nguyn ngoi bo v t bo T loi b khng nguyn ni bo. Chc nng ny ca khng th v t bo T thng yu cu s tham gia ca cc t bo hiu qu khc khng thuc h lymph v c c ch khng ca min dch bm sinh. Nh vy, cng nhng c ch min dch bm sinh hot ng nh phng tuyn u tin nhng v sau li cn tham gia vo phng tuyn th hai ca min dch thu c loi b khng nguyn ra khi c th. Tht ra, nh ni trn, mt chc nng quan trng ca p ng min dch thu c l nhm tng cng c ch hiu qu ca min dch bm sinh v hng nhng c ch hiu qu ny vo cc m hoc t bo cha khng nguyn l.

1.5.4. Tnh hng nh ni mi: gim dn p ng min dch Vo cui p ng min dch, h thng min dch tr li trng thi ngh c bn do phn ln cc t bo tin thn (progeny) ca lymph b khng nguyn kch thch cht do hin tng cht lp trnh (apoptosis). Cht lp trnh l mt dng cht sinh l c chun b trc, trong nhn t bo b c li v v ra tng mnh, mng bo tng ni bt, khng cn s tch bit ca lp lipid mng v t bo cht nhanh chng b thc bo m cc cht ni bo khng cn b gii phng ra ngoi (qu trnh cht ny ngc vi kiu cht hoi t, trong nhn v mng bo tng b phn gii v cc cht ni bo b v ra ngoi to ra mt phn ng vim ti ch). Mt lng ln t bo lymph b khng nguyn kch thch s cht i theo kiu lp trnh. Gii thch iu ny, ngi ta cho rng c l do s tn ti ca lymph bo ph thuc vo khng nguyn v cc yu t pht trin do khng nguyn khi ng nn khi p ng min dch loi b ht khng nguyn th t bo lymph khng cn nhn c nhng kch thch cn thit cho s sng.

CC C QUAN CA H THNG MIN DCH 2.1. Cc m lymph M lymph c phn loi thnh c quan lymph trung ng (hay c quan lymph s cp) l ni m t bo lymph ln u tin th hin th th khng nguyn v trng thnh v mt chc nng v c quan lymph ngoi bin (hay c quan lymph th cp) l ni xy ra p ng ca t bo lymph vi khng nguyn l. C quan lymph trung ng ca ng vt c v bao gm tu xng, ni sn xut ra ton b t bo lymph, v tuyn c, ni t bo T trng thnh v t n giai on pht trin chc nng y . C quan v m lymph ngoi bin bao gm hch bch huyt, lch, h thng min dch da v h thng min dch nim mc. Ngoi ra, ngi ta cn tm thy mt s t bo lymph trong cc m lin kt v tt c cc c quan tr h thn kinh trung ng.

2.1.1. Tu xng ngi trng thnh, tu xng l ni sn sinh tt c cc t bo mu lu ng k c t bo lymph non. Tu xng cng l ni trng thnh ca t bo B. Trong qu trnh pht trin bo thai, s sn xut t bo mu, gi l qu trnh to mu, xut hin u tin trong cc o mu ca ti phi v trong nhu m cnh ng mch ch v sau th ti gan v lch. Chc nng ny c chuyn giao dn dn cho tu xng v c bit l cc xng dt sao cho n tui dy th th chc nng to mu ch yu xy ra xng c, t sng, xng chu v xng sn. Tu l loi tu ca cc xng ny c tm thy trong mt cu to li dng m xp nm gia cc b di. Khong khng gia cc cu to ny c lm y bi t bo m, nguyn bo si, v t bo tin thn ca t bo mu. Nhng t bo tin thn ny s pht trin n trng thnh v i ra khi tu qua mt h thng dy c cc

xoang mch vo h tun hon. Khi tu xng b tn thng, hoc khi c cc nhu cu to nhiu t bo mu mi th gan v lch cng c huy ng lm chc nng to mu. Tt c t bo mu u xut pht t mt loi t bo gi l t bo mm, nhng t bo ny ri s phn ho to ra nhiu dng t bo mu khc nhau (bao gm dng tu, dng i nguyn hng cu, dng ht, dng lymph) (Hnh 2.1). T bo mm khng c cc du n ca t bo bit ho v thay vo l 2 protein mng c tn l CD34 v khng nguyn-1 ca t bo mm (Sca-1). Nhng du n ny dng nhn din v lm giu t bo mm t cc hn dch tu xng dng cho ghp tu. S tng sinh v trng thnh ca t bo mu tin thn trong tu xng c kch thch bi cc cytokin. C nhiu cytokin c tn gi l yu t kch thch colony (colony-stimulating factor) v ban u ngi ta kho st chng qua chc nng kch thch s pht trin ca nhiu colony dng bch cu v dng hng cu trong tu xng. Cc cytokin to mu c sn xut bi t bo m v i thc bo trong tu xng to nn mt mi trng to mu thun li. Chng cng c sn xut bi t bo T c khng nguyn kch thch hoc cc i thc bo b cytokin hay vi sinh vt kch thch to nn mt c ch b sung cho cc bch cu b tiu hao do phn ng min dch hoc vim.

Hnh 2.1. S ca hot ng to mu S pht trin ca cc dng t bo mu c tm tt trong cy to mu ny. Ngoi cc t bo mm v cc th h t bo tip theo do chng sinh ra, tu xng cn cha nhiu Z tng bo sn xut khng th. Nhng tng bo ny c to ra trong m lymph ngoi bin (do s kch thch ca khng nguyn ln t bo B) v di chuyn vo tu xng, chng s sng y v sn xut khng th trong nhiu nm. 2.1.2. Tuyn c Tuyn c l ni trng thnh ca t bo T. Tuyn c l mt c quan c hai thu nm trung tht trc. Mi thu c phn chia thnh nhiu tiu thu ngn cch nhau bi cc vch si v mi tiu thu c vng v bn ngoi v vng tu bn trong (Hnh 2.2). Vng tu cha dy c t bo T lymph v vng tu th t t bo hn nhng cng ch yu l t bo lymph. Ri rc trong tuyn c l cc t bo biu m khng phi lymph ( l nhng t bo c nhiu bo tng), i thc bo c ngun gc tu xng v t bo hnh sao. Mt s t bo hnh sao trong tuyn c c mang cc du n nh CD8a l du n c trng ca t bo lymph nn c gi l t bo hnh sao dng lymph phn bit vi t bo hnh sao dng tu trnh by phn trn. vng tu c nhng cu trc gi l tiu th Hassall c cu to bi nhng vng xon t bo biu m m c l l vt tch ca cc t bo thoi ho. Tuyn c c cung cp mch mu rt di do v c nhng mch i dn n h thng bch mch vng trung tht. Tuyn c c hnh thnh trong qu trnh lm vo ca ngoi b (ectoderm) trong thi k bo thai to nn c v ngc. Trong mt dng chut tri lng c bit, mt t bin gen lm cho chng mt kh nng bit ho cc t bo biu m l t bo cn thit hnh thnh tuyn c v cc nang to lng. Kt qu l chut ny khng c t bo T v khng c lng. ngi, nhng tr c hi chng DiGeorge cng khng c t bo T do t bin gen cn thit cho s hnh thnh tuyn c.

Hnh 2.2. Hnh thi tuyn c A. Hnh nh knh hin vi quang hc ca mt thu tuyn c cho thy c vng tu v vng v. T bo bt thuc nhum xanh gi l t bo tuyn c l lymph bo T ang trng thnh . B. S tuyn c cho thy thu c chia thnh nhiu tiu thu ngn cch bi cc b si.

T bo lymph trong tuyn c, cn c gi l t bo tuyn c, l t bo T cc giai on pht trin khc nhau. Ni chung, hu ht t bo T non u i vo v tuyn c qua h thng mch mu. S trng thnh xy ra trong vng

v, v khi t bo tuyn c trng thnh chng s di c qua vng tu, do vng tu cha ch yu l t bo T trng thnh. Ch c t bo T trng thnh mi i ra khi tuyn c vo mu v m lymph ngoi bin. 2.1.3. Hch bch huyt v h thng bch mch Hch bch huyt l nhng c quan nh dng nt ca m lymph c tm thy dc theo h thng bch mch khp c th. Mt hch bch huyt c vng v bn ngoi v vng tu bn trong. Mi hch c bao bc bi mt nang si c nhiu mch bch huyt n xuyn qua a bch huyt vo vng di v tc vo cc xoang nm st mt ngoi ca hch. Bch mch thm qua vng v vo vng tu v ri hch qua cc bch mch i vng rn hch. Bn di nhng tiu mao mch ca lp v l nhng m t bo tp trung dy c c gi l nang. Mt s nang c gia mt trung tm mm bt thuc nhm nht hn. Nhng nang khng c trung tm mm c gi l nang s cp, cn nhng nang c trung tm mm c gi l nang th cp. Vng v xung quanh nang c t chc thnh nhng khong khng gian hnh di cha t bo lymph, t bo hnh sao v thc bo n nhn; nhng t bo ny c b tr xung quanh nhng xoang bch mch v mu. T bo lymph v t bo trnh din khng nguyn trong nhng khong khng gian ny thng nm cnh nhau nhng khng to nn nhng cu ni lin bo v iu ny cn thit t bo lymph c th di chuyn v lu thng trong mu, h bch mch hoc cc m. Bn di vng v l vng tu c cu to bi nhng di tu dn n nhng xoang tu. Nhng di ny cha i thc bo v tng bo. Mu c dn vo hch qua mt ng mch n i vo rn hch ri chia nhnh nh dn thnh cc mao mch n vng v ngoi. Mu i khi hch qua mt tnh mch duy nht vng rn. Cc loi t bo lymph khc nhau c b tr nhng vng ring bit trong hch bch huyt (Hnh 2.3). Cc nang l vng ca t bo B. Nang s cp cha ch yu l t bo B trng thnh v cn nguyn vn. Cc trung tm mm c to ra khi c p ng khng nguyn. l ni xy ra tng sinh t bo B, la chn t bo B sn xut khng nguyn c tnh c hiu cao, v sn xut ra t bo B nh. Cc si tua bo tng ca t bo hnh sao vng nang an xen vo nhau to ra mt cu trc hnh li dy c trong trung tm mm. T bo lymph T c b tr ch yu bn di v gia cc nang, trong vng v. a s (khong 70%) t bo T l t bo T gip CD4+,

trn ln vi mt s ri rc t bo CD8+. T bo hnh sao cng tp trung vng t bo T trong hch bch huyt. S chia tch v mt gii phu ca cc loi t bo lymph trong hch bch huyt l qu trnh ph thuc vo cytokin (Hnh 2.3). T bo lymph T v B nguyn vn c a vo hch qua ng mch. Nhng t bo ny ri tun hon v i vo vng m ca hch qua mt loi mch mu c bit gi l tiu tnh mch giu ni m nm vng v. T bo T nguyn vn c mang mt th th dnh cho mt cytokin hp dn ho hc gi l chemokin; th th ny c tn l CCR7. CCR7 ch nhn din nhng chemokin c sn xut trong vng t bo T ca hch bch huyt, v nhng chemokin ny c chc nng thu ht t bo T nguyn vn vo vng t bo T ny. T bo hnh sao cng mang CCR7, v l l do v sao chng di c vo cng mt ni vi t bo T nguyn vn trong hch. T bo B nguyn vn mang th th ca mt chemokin khc l CXCR5 c chc nng nhn din mt chemokin ch c sn xut trong nang. V th m t bo B c thu ht vo nang l vng ca t bo B trong hch bch huyt. C mt chemokin khc c tn l lymphotoxin c kh nng kch thch s sn xut chemokin cc vng khc nhau trong hch, nht l vng nang. Ngi ta xc nh chc nng ca cc cytokin khc nhau nh vo cc th nghim trn chut.

Hnh 2.3. S chia tch cc vng ca t bo B v T trong hch A. S v cc ng xm nhp ca t bo T v B vo hch bch huyt.

1.

Trong tiu bn ny ca hch bch huyt, t bo B trong cc nang c nhum xanh, cn t bo T vng v cn nang th nhum (theo phng php nhum min dch hunh quang).

S phn cch v mt gii phu ca t bo T v B l nhm m bo cho mi t bo c tip xc trc tip vi t bo trnh din khng nguyn thch hp (v d t bo T th tip xc vi t bo hnh sao cn t bo B th vi t bo hnh sao vng nang). Hn na, s phn cch chnh xc ny gip cho cc qun th t bo T v B c gi ring r nhau cho n khi cn tng tc thc hin chc nng. Sau khi c khng nguyn kch thch, t bo T v B mt s ngn cch v mt gii phu v di chuyn v pha nhau. T bo T hot ho cui cng ri c th i ra khi hch vo tun hon, trong khi t bo B tin vo cc trung tm mm hoc vng tu, t chng s tit ra khng th.

Hnh 2.4. H thng bch mch Hnh bn phi l s h thng bch mch v cc hch bch huyt ch yu. Hnh bn tri minh ho cch khng nguyn c bt gi v chuyn n

hch bch huyt to ra p ng min dch.

Khng nguyn c vn chuyn n hch ch yu qua h thng bch mch. H bch mch m trch chc nng thu thp v vn chuyn khng nguyn t ni xm nhp n hch bch huyt (Hnh 2.4). Da, biu m v nhng c quan c nhu m cha rt nhiu mao mch bch huyt l ni hp th v vn chuyn dch gian bo (thot ra t bo tng) i khi cc ni ny. Dch gian bo c hp th vo c gi l bch huyt, n s di chuyn dn qua cc mao mch ln hn cui cng vo mt mch bch huyt ln nht gi l ng ngc. Bch huyt t ng ngc c vo tnh mch ch trn tr li h tun hon. Mi ngy c nhiu lt bch huyt c vo h tun hon, do tc h bch mch s nhanh chng dn n ph cc m. Vi sinh vt thng xm nhp vo c th qua da, ng tiu ho v h hp. Tt c cc m ny u c bao ph bi mt lp biu m cha nhiu t bo hnh sao. T bo hnh sao bt gi khng nguyn vi sinh vt v di chuyn vo bch mch. Cc hch bch huyt c b tr dc theo h bch mch v hot ng nh nhng c quan lc mu vt trong bch huyt trc khi bch huyt vo h tun hon. Nh vy khi khng nguyn b bt gi n s c chuyn n hch bch huyt. Nhng khng nguyn khng phi l t bo cng c th c vn chuyn trong bch mch. Mch bch huyt a bch huyt n hch c gi l bch mch n, cn bch mch dn bch huyt ra khi hch c gi l bch mch i. Bi v cc hch bch huyt to thnh chui dc theo bch mch nn mt mch i ca hch ny c th l mch n ca hch kia. Khi bch huyt i vo mt hch bch huyt qua h thng bch mch, n s thm vo vng m ca hch. Cc t bo hnh sao mang khng nguyn s i vo vng t bo T v li vng ny. Cc khng nguyn ho tan n theo bch mch c th c t bo hnh sao hoc i thc bo hin din trong vng m ca hch thu thp. Kt qu l khng nguyn c tp trung vi m cao hn hch trnh din cho t bo T c hiu. 2.1.4. Lch

Hnh 2.5. Hnh thi hc ca lch A. trng. S cu to ca lch vi cc vng t bo T v B to nn nhu m

B. Hnh nh knh hin vi quang hc ca tiu bn lch vi ng mch c b si v nang lymph.1.

Hnh nh nhum ho min dch ca tiu bn lch. Vng t bo T mu

v t bo B mu xanh. Lch l v tr ch yu ca p ng min dch i vi khng nguyn n t mu. Lch l mt c quan nng 150gam ngi ln, nm trong bng, vng h sn tri. Lch c ti mu bi mt ng mch duy nht l ng mch lch. Khi i vo lch ng mch chia nhiu nhnh nh dn; cc nhnh ny c bao bc v nng bi cc b si (Hnh 2.5). Cc tiu ng mch nh c bao bc bi t bo lymph, l vng t bo T ca lch. Do v tr gii phu ca n, cc nh hnh thi hc gi vng ny tm lymph quanh tiu ng mch. Cc nang lymph (mt s c trung tm mm) c gn lin vi vng t bo T ging nh trong hch. Nang lymph l vng t bo B. Cc nang ny c bao bc bi mt vng t bo lymph v i thc bo gi l vng vin. Nhng m dy c t bo lymph ny to nn m lch trng. Cc tiu ng mch cui cng vo cc xoang mch nm ri rc trong lch. Cc xoang ny cha ch yu l hng cu, i thc bo, t bo hnh sao, mt t t bo lymph v tng bo. Cc xoang ny to nn m tu ca lch. T cc xoang mu s v tnh mch lch sau i khi lch qua h thng tun hon ca. Cc loi t bo lymph c phn b tch bit trong lch ging nh trong hch v c ch ca s tch bit ny ging nhau c hai c quan (Hnh 2.3). Khng nguyn v t bo lymph i vo lch qua cc xoang mch mu. Khi chemokin c sn xut th t bo T c thu ht n vng t bo T nm bn cnh cc tiu ng mch, cn t bo B th i vo cc nang. Lch l mt c quan lc mu quan trng. Cc i thc bo trong m lch chu trch nhim lm sch cc vi sinh vt v vt l khc c trong mu; ng thi lch l ni ch yu thc hin vic thc bo cc vi sinh vt c gn khng th (tc l opsonin ho). Nhng c th mt lch rt d b nhim trng i vi cc vi khun c v bc nh ph cu, mng no cu v nhng vi khun ny thng c loi b nh s opsonin ha v thc bo v khi mt lch th chc nng ny khng thc hin c. 2.1.5. H thng min dch da Da c cha mt h thng min dch c chuyn mn ho bao gm t bo lymph v t bo trnh din khng nguyn. Da l c quan rng nht trong c th to nn hng ro vt l quan trng nht ngn cch c th vi vi sinh vt v cc vt l ca mi trng bn ngoi. Da cn l mt b phn tch cc

ca h thng bo v c th c kh nng to ra phn ng vim v p ng min dch ti ch. Nhiu khng nguyn l i vo c th qua ng da, do da cng l ni khi ng nhiu p ng min dch ton thn khc. Qun th t bo chnh trong lp biu m l t bo sng (keratinocyte), t bo hc t (melanocyte), t bo Langerhans biu m v t bo T trong biu m (intraepithelial T cell) (Hnh 2.6). T bo sng v t bo hc t hnh nh khng c vai tr quan trng trong min dch thu c, mc d t bo sng c th sn xut nhiu cytokin ng gp cho phn ng min dch bm sinh v phn ng vim da. T bo Langerhanx nm pha trn lp mng cn bn ca biu m, y l nhng t bo hnh sao cha trng thnh ca h thng min dch da. T bo Langerhans to nn mt mng li gn nh lin tc cho php bt gi hu nh ton b nhng khng nguyn no xm nhp vo c th qua da. Khi b kch thch bi cc cytokin tin vim, t bo Langerhans s co cc si tua ca mnh li, mt tnh kt dnh vi t bo biu m v di chuyn vo lp b. Sau chng theo ng bch mch tr v nh ca chng l cc hch bch huyt, qu trnh ny c kch thch bi cc chemokin ch tc ng c hiu ln t bo Langerhans.

Hnh 2.6. Cc thnh phn t bo ca h thng min dch da

Thnh phn ch yu ca h thng min dch da trong s ny l t bo sng, Langerhans, v lymph trong biu m, tt c u nm trong lp biu m; v cc t bo cn li bao gm t bo T v i thc bo th nm trong lp b. T bo lymph trong biu m chim ch 2% t bo lymph lin quan n da (s t bo lymph cn li nm lp b), v chng a s l t bo T CD8+. T bo T trong biu m c th mang mt b th th khng nguyn c tnh hn ch cao hn t bo lymph T a s cc m ngoi da. chut nht (v mt s loi khc), nhiu t bo lymph trong biu m l t bo T mang mt loi th th khng nguyn to bi chui g v d thay v chui a v b thng thng nh t bo T CD4+ v CD8+. Lp b c cha t bo lymph T (c CD4+ v CD8+), ch yu xung quanh cc mch mu, v ri rc trong lp b l i thc bo. iu ny cng tng t nh cc m lin kt cc c quan khc. T bo T thng mang cc du n kiu hnh c trng cho t bo nh hoc t bo hot ho. Ngi ta cng cha r y l nhng t bo thng xuyn c tr trong lp b hay ch li thong qua khi dng mu v bch mch mang chng n y. Nhiu t bo T lp b cn mang mt epitop hydrat cc-bon c tn l khng nguyn-1 lymph bo da, khng nguyn ny c tham gia vo qu trnh di chuyn c hiu ca t bo v da. 2.1.6. H thng min dch nim mc Trong lp nim mc ca h tiu ho v h hp c t tp ca nhiu t bo lymph v v t bo trnh din khng nguyn c vai tr khi ng p ng min dch i vi khng nguyn ng tiu ho (n vo) v h hp (ht vo). Cng ging nh da, lp biu m nim mc l hng ro quan trng ngn cn s xm nhp ca vi sinh vt. Nhng hiu bit ca chng ta v min dch nim mc da ch yu vo nhng nghin cu ng tiu ho, cn nhng hiu bit v min dch nim mc h hp th rt t mc d y cng l ng xm nhp rt thng xuyn ca vi sinh vt. Tuy nhin, hnh nh cc kha cnh ca p ng min dch ging nhau c hai m lymph nim mc ny.

Hnh 2.7. H thng min dch nim mc S cc thnh phn t bo ca h thng min dch nim mc. 2. Hnh nh knh hin vi quang hc ca m lymph nim mc rut tha ngi. Ngi ta tm thy nhng m t bo lymph ging nhau nm ri rc dc theo ng tiu ho v ng h hp.1.

Trong nim mc ca ng tiu ho, rt nhiu t bo lymph tp trung ba khu vc: trong lp biu m, phn tn rng ri cc lamina propria, v nhng tm Peyer (tc l nhng lamina propria c t chc li) (Hnh 2.7). T bo ti mi khu vc c c im kiu hnh v chc nng khc nhau. a s lymph trong biu m l t bo T. ngi, phn ln nhng t bo ny l

CD8+. chut nht, khong 50% t bo lymph trong biu m mang th th t bo T (TCR) dng gd, tng t nh lymph bo trong biu m da. ngi ch 10% t bo lymph trong biu m l gd, nhng t l ny vn cn cao hn t l t bo gd trong cc m khc. T bo lymph trong biu m mang TCR ab v gd c tnh a dng v th th khng nguyn rt thp. Tt cc nhng pht hin va cp u ph hp vi kin cho rng lymph bo trong biu m rt hn ch v tnh c hiu, khc vi hu ht vi cc t bo T khc. Cc lamina propria trong ng tiu ho cha nhiu loi t bo khc nhau, bao gm lymph T, m a s l CD4+, c kiu hnh ca t bo hot ho. Ngi ta nhn thy rng u tin t bo T i ra khi rut non nhn din v p ng vi khng nguyn trong hch mc treo ri quay tr li rut non v tp trung lamina propria. iu ny cng ging nh ngun gc gi nh ca t bo T trong lp b ca da. Lamina propria cn cha nhiu t bo B hot ho v tng bo cng nh i thc bo, t bo hnh sao, t bo i toan v dng bo (t bo mast). Bn cnh nhng t bo lymph nm ri rc khp ni trong nim mc rut, h thng min dch nim mc cn cha nhng m lymph c t chc ho, m ni bt nht l cc tm Peyer ca rut non. Cng ging nh cc nang lymph lch v hch, vng trung tm ca nhng nang nim mc ny l vng giu t bo B. Cc tm Peyer cn cha mt lng nh t bo T CD4+, ch yu l nm vng lin nang. chut nht trng thnh, 50% 70% lymph bo ca tm Peyer l t bo B, v 10% - 30% l t bo T. C mt s t bo biu m nm ph ln tm Peyer, l nhng t bo M (mng) c chuyn mn ho. T bo M khng c vi mao, bt gi vt l mt cch ch ng v vn chuyn cc i phn t t lng rut non vo m di biu m. Cc t bo M ny ng vai tr quan trng trong vic a khng nguyn n cho cc tm Peyer. (Lu rng t bo M khng c chc nng ging nh t bo trnh din khng nguyn). Cc nang ging nh tm Peyer hin din rt nhiu trong rut tha, cn trong ng tiu ho v h hp th t thi. Hch hnh nhn c cng l cc cu to nang lymph nim mc tng t nh tm Peyer. p ng min dch i vi khng nguyn ng ming c mt s im khc bit c bn vi p ng i vi khng nguyn xm nhp vo c th theo cc ng khc. Hai im khc bit ni bt l: mc sn xut khng th IgA rt cao trong m nim mc, v min dch ng ming i vi khng

nguyn protein c xu hng to ra dung np t bo T hn l hot ho t bo T.

2.2. Cc con ng v c ch ti tun hon v homing ca t bo lymph T bo lymph lin tc di chuyn trong mu v bch mch, t m lymph ngoi bin (th cp) ny n m lymph ngoi bin khc v n a im vim ngoi bin (Hnh 2.8). S di chuyn ca t bo lymph gia cc v tr ny c gi l s ti tun hon lymph bo, v hin tng nhng tiu qun th lymph c bit c chn lc i vo nhng m nht nh m khng i vo cc m khc c gi l hin tng homing (v nh) ca t bo lymph. Hin tng ti tun hon gip cho lymph bo thc hin nhng chc nng quan trng ca mnh trong p ng min dch thu c. Trc ht, n gip cho mt t bo lymph c th tm ra khng nguyn tng ng ca mnh d khng nguyn bt c ni no trong c th. Th hai, n m bo cho mt tiu qun th lymph c th c a n mt vi mi trng thch hp trong m to ra p ng min dch ch khng a n mt ni m chng khng to c hiu qu no c. V d, con ng ti tun hon ca t bo lymph nguyn vn khc vi con ng ca t bo hiu qu v t bo nh, v s khc bit ny rt quan trng cho tng giai on khc nhau ca p ng min dch. Ni mt cch c th, t bo lymph nguyn vn ti tun hon qua cc c quan lymph ngoi bin, t bo lymph hiu qu th di chuyn n cc m ngoi bin ni c nhim trng v vim. Nhng iu c ni y lin quan ch yu n t bo T v nhng hiu bit v ti tun hon t bo B cn rt hn ch. S ti tun hon v di chuyn ca lymph bo n nhng m nht nh c trung gian bi cc phn t kt dnh hin din trn t bo lymph, t bo ni m v gian cht ngoi bo, cng nh trung gian ca cc chemokin trong lp t bo ni m v trong cc m. S kt dnh hoc khng ca t bo lymph vi t bo ni m nm cc tiu tnh mch sau mao mch trong mt m no s quyt nh t bo lymph c i vo m hay khng. S kt dnh v tch ri cc thnh phn gian cht ngoi bo trong mt m s quyt nh t bo lymph li bao lu trong vng ngoi bo trc khi vo bch mch vo mu. Cc phn t kt dnh trn b mt lymph bo c gi l th th homing (homing receptor), cn u kt ni tng ng (ligand) ca chng trn t bo ni m c gi l addressin. Th th homing trn t bo

lymph bao gm ba h phn t: selectin, integrin v siu h (superfamily) Ig. Nhng th th homing ny hon ton khc vi th th khng nguyn, v quy trnh ti tun hon c lp vi khng nguyn. Vai tr duy nht ca nhn din khng nguyn trong ti tun hon lymph bo l lm tng i lc (affinity) ca integrin trn lymph bo i vi cc u ni tng ng ca chng dn n s duy tr ca cc t bo ti ni hin din ca khng nguyn.

2.2.1. Ti tun hon lymph bo nguyn vn qua cc c quan ngoi bin T bo T nguyn vn c xu hng homing v ti tun hon qua cc c quan lymph ngoi bin chng s nhn dng v p ng vi khng nguyn. Lung t bo lymph di chuyn qua hch rt ln; ngi ta c tnh mi ngy c khong 25x109 t bo i qua hch (tc trung bnh mt lymph bo i qua mi hch mt ln trong ngy). Khng nguyn c tp trung trong hch v lch, chng c trnh din bi t bo trnh din khng nguyn hoc t bo hnh sao trng thnh kch thch p ng t cc t bo T nguyn vn. Nh vy vic di chuyn ca t bo lymph nguyn vn ngang qua cc hch lymph v lch l nhm tng c hi ti a cho vic tm gp khng nguyn tng ng v khi ng p ng min dch thu c.

Hnh 2.8. Cc con ng ti tun hon ca lymph bo T T bo T nguyn vn c xu hng ri mch mu vo hch khu vc tiu tnh mch giu ni m. T bo hnh sao mang khng nguyn s i vo hch qua ng bch huyt. Nu t bo T nhn din khng nguyn, chng c hot ho v tr v mu qua bch mch, v ng ngc, tnh mch ch trn v vo tim tr li tun hon ng mch.

Hnh 2.9. Tiu tnh mch giu ni m A. Hnh nh knh hin vi quang hc ca tiu tnh mch giu ni m trong hch bch huyt. B. Th hin ca u lin kt L-selectin trn tiu tnh mch giu ni m. C. Hnh nh t bo lymph gn mt cch chn lc vo t bo ni m ca tiu tnh mch giu ni m. D. Hnh nh knh hin vi in t (qut) ca t bo lymph gn vo

tiu tnh mch giu ni m. Khi i vo hch, t bo lymph nguyn vn s ri h tun hon mt vng mch mu c cu to gii phu c bit gi l tiu tnh mch giu ni m (high endothelial venule) (Hnh 2.9). Tiu tnh mch giu ni m cn c th gp trong m lymph nim mc (ti tm Peyer ca rut) nhng khng c trong lch. T bo T nguyn vn di chuyn t h tun hon vo vng m ca hch tri qua mt chui nhiu bc tng tc gia t bo v t bo ni m trong tiu tnh mch giu ni m. Chui tng tc ny, cng ging nh trong qu trnh di chuyn ca bch cu vo cc m ngoi bin, bao gm ban u l bc tng tc i lc thp qua trung gian ca selectin, v sau l bc tng cng i lc integrin ca t bo T do chemokin lm trung gian, v cui cng l bc dnh cht t bo T vo tiu tnh mch giu ni m qua trung gian ca integrin. T bo lymph nguyn vn mang mt th th homing thuc h selectin c tn l L-selectin (CD62L). Cc tiu tnh mch giu ni m c cha nhng glycosaminoglycan sulfat c gi bng tn chung l addressin hch ngoi bin (peripheral node addressin, PNAd); y l nhng u lin kt (ligand) ca L-selectin. Cc gc ng lin kt vi L-selectin c th c gn vi nhiu sialomucin khc nhau trn t bo ni m ca nhiu m khc nhau. V d, trn tiu tnh mch giu ni m ca hch bch huyt, PNAd c th lm cho bc l nh hai sialomucin gi l GlyCAM-1 (phn t kt dnh t bo s 1 mang glycan) v CD34. Trong cc tm Peyer ca ng tiu ho, u kt ni L-selectin l mt phn t c tn l MadCAM-1 (phn t kt dnh t bo s 1 mang addressin nim mc). Nh vy, nhng phn t khc nhau mang u lin kt ng i vi L-selectin c th ng vai tr quan trng trong vic t tp t bo T nguyn vn n lp ni m ca nhng m khc nhau. S lin kt ca L-selectin vo u lin kt ca n l mt tng tc c i lc yu v d t do lc ct ca dng huyt ng. Kt qu l cc t bo T dnh vo tiu tnh mch giu ni m vi lc dnh lng lo trong mt vi giy, ri li tch ra, dnh vo v ln trn b mt ni m. Trong lc , cc chemokin c sn xut trong hch c th xut hin trn b mt ca t bo ni m gn glycosaminoglycan. T bo T ln trn lp ni m c th gp cc chemokin ny v gia tng lc kt dnh, c th co dn thnh dng vn ng v trn qua khe h gia cc t bo ni m vo vng m ca hch. T bo lymph i khi tiu tnh mch giu ni m nh vo chnh nng chemokin. Nh cp trc y, t bo T nguyn vn c mang th th CCR7 v di chuyn vo vng t bo T l vng sn xut ra chemokin c i tnh vi CCR7; cn t bo B mang CXCR5 nn di chuyn vo vng nang l ni sn xut chemokin lin kt vi CXCR5. Vai tr quan trng ca L-selectin v chemokin trong hin tng homing ca t bo lymph v cc m lymph th cp c nhiu

tc gi chng minh bng thc nghim. Hin nay, ngi ta cn t bit v bn cht ca th th homing hay addressin tham gia vo qu trnh ti tun hon t bo lymph ngang qua lch, mc d bit rng t l ca lng lymph bo qua lch trong 24 gi bng mt na tng s t bo lymph. Phn t MadCAM-1 trn b mt t bo ni m nm cc xoang mch xung quanh vng t bo T ca lch hnh nh c lin quan n hin tng homing ca t bo T nguyn vn. Lch khng c cc tiu tnh mch giu ni m c th nhn ra bng hnh thi hc, v c l hin tng homing ca lymph bo v lch khng c tnh chn lc nh cc lymph bo homing v hch. T bo nguyn vn i vo hch c th c hot ho bi nhng khng nguyn c vn chuyn n hch. Sau mt vi gi tip xc vi khng nguyn ngoi bin, lng mu n mch c th c huy ng tng ln hn 20 ln nhm lm tng s lng t bo lymph nguyn vn n v tr c khng nguyn. ng thi, lc ny lng mu ra khi hch gim i. Nhng thay i ny l do mt phn ng vim chng li vi sinh vt hay chng li t cht i cng khng nguyn. T bo T nguyn vn i vo vng t bo T ca hch s r sot ton b t bo hnh sao trong vng ny tm ra khng nguyn v nhn din chng. Khi nhn din khng nguyn, t bo T chu s tng sinh pht trin cln, ri bit ho thnh t bo hiu qu hoc t bo nh sau bc vo cc con ng ti tun hon khc nhau. Nu t bo T khng nhn din khng nguyn chng s i ra khi hch theo bch mch i vo h tun hon v ri homing ti mt hch khc. 2.2.2. S di c ca lymph bo hiu qu v lymph bo nh n ni c vim T bo T hiu qu v T nh i ra khi hch v c xu hng mun di c n cc m ngoi bin ni c nhim trng; ti chng s lm nhim v loi b vi sinh vt, l giai on hiu qu p ng min dch thu c. S bit ho ca t bo T nguyn vn thnh t bo hiu qu trong c quan lymph ngoi bin ko theo s thay i ca nhiu phn t kt dnh. S th hin ca L-selectin gim xung, nhng s lng mt s integrin, cc u lin kt ca E- v P-selectin v CD44 th gia tng. S bit ho ca t bo T hiu qu cng gy ra mt th th chemokin CCR7. Do , t bo hiu qu khng cn c gi li trong hch na, chng s theo bch mch i vo h tun hon. Ti v tr nhim trng, phn ng min dch bm sinh sn xut ra nhiu cytokin. Mt s cytokin ny tc ng ln ni m mch mu ti ch kch thch th hin cc u lin kt i vi integrin v E- cng nh P-selectin. ng thi

chng cng kch thch tit mt s chemokin tc ng ln t bo T. Nhng chemokin ny lm tng i lc lin kt ca integrin trn t bo T vo cc u lin kt ca n. Nh vy, t bo T bm cht vo t bo ni m v chui ra khi thnh mch n v tr nhim trng. Bi v cc integrin v CD44 cng lin kt vi cc protein ca c cht ngoi bo nn t bo T hiu qu c lu gi li ti cc ni ny. Do t bo hiu qu c th thc hin chc nng loi b nhim trng ca chng. T bo T nh rt a dng v cch thc th hin cc phn t kt dnh v xu hng di c n nhng m khc nhau. Mt s t bo nh di chuyn n m da v nim mc; mt s phn t kt dnh ng vai tr quan trng trong qu trnh ny. V d, mt s t bo nh mang integrin (a 4b6) l phn t c th tng tc vi addressin MadCAM ca t bo ni m nim mc v nh th kch thch qu trnh homing ca t bo T nh v m lymph nim mc. T bo T nh trong biu m ng tiu ho mang mt integrin khc (aEb7) l phn t c th kt ni vi phn t E-cadherin trn t bo biu m, v cho php t bo T lu li nh nhng lymph bo trong biu m. Nhng t bo T nh khc c xu hng di c v da mang mt u kt ni cacbon hyrat c tn l CLA-1 (cutaneous lymphocyte antigen-1) c kh nng kt ni vi E-selectin. Li cn nhng t bo nh khc mang L-selectin v CCR7, v nhng t bo ny c xu hng di chuyn n hch bch huyt, chng c th m rng cln nhanh chng nu gp khng nguyn thch hp.

2.2.3. Ti tun hon ca lymph bo B V nguyn tc, s di chuyn ca t bo lymph B n cc m khc nhau cng ging nh s di chuyn ca t bo T v c iu ho bi c ch phn t tng t. T bo B nguyn vn di chuyn n hch, c th l n cc nang nh vo s dng cc th th L-selectin v chemokin CXCR5. Khi c hot ho, t bo B mt i phn t b mt CXCR5 v i khi nang vo vng t bo T ca c quan lymph. T bo T hot ho c mang cc integrin v dng chng di chuyn n cc m ngoi bin. Mt s tng bo sn xut khng th di chuyn vo tu xng; phn t no tham gia vo vic ny th cha r. Cc t bo tit khng th khc li trong c quan lymph v khng th do chng sn xut s i vo tun hon tm khng nguyn trong khp c th.

KHNG TH Mt trong nhng thng bo thc nghim u tin v p ng min dch thu c l s trnh by v min dch dch th chng li c t vi khun. Vo nhng nm u ca thp k 1900, bnh nhn b nhim trng bch hu c th b nguy him tnh mng nhng c th iu tr c bng cch tim huyt thanh ca nhng nga c gy min dch vi c t bch hu. Th dng min dch ny c gi l min dch dch th v c trung gian bi mt h glycoprotein c tn l khng th. Khng th, phn t MHC (phc h ho hp m ch yu), v th th khng nguyn ca t bo T l ba loi phn t tham gia vo vic nhn din khng nguyn trong min dch thu c. Trong ba loi phn t ny th khng th lin kt vi nhiu cu trc khng nguyn nht, c kh nng tt nht trong vic phn bit cc khng nguyn khc nhau, v lin kt vi khng nguyn vi lc mnh nht. Khng th cng l phn t c nghin cu nhiu nht trong ba phn t lin kt khng nguyn ny.

3.1. Phn b t nhin v sn xut khng th Khng th c phn b trong cc dch sinh hc khp c th v c tm thy trn b mt mt s t bo. Lymph bo B l t bo duy nht sinh tng hp c phn t khng th. Trong t bo B, khng th hin din trong cc b phn lin kt vi mang trong bo tng (nh h li ni bo v h Golgi) v trn b mt t bo ni m chng c xem nh l mt protein mng. Dng tit ca khng th hin din trong huyt tng, dch nim mc, v dch gian bo ca cc m. Khng th do t bo B tng hp v sn xut s gn ln b mt ca mt s t bo hiu qu min dch nh thc bo n nhn, t bo NK (git t nhin), v dng bo l nhng t bo c th th c hiu dnh cho phn t khng th. Khi mu hay huyt tng to thnh cc ng, khng th nm trong khi dch cn li gi l huyt thanh. Huyt thanh c cha khng th chng li mt khng nguyn nht nh no c gi l khng huyt thanh. (Do , nhng nghin cu v khng th v tng tc ca n vi khng nguyn c gi mt cch kinh in l huyt thanh hc). Nng ca khng th trong huyt thanh chng li mt khng nguyn c bit no thng c o bng cch tnh xem n pha long no th phn ng gia khng nguyn v khng th khng cn thy c na. pha long c gi l hiu gi

khng th. Mt ngi ln kho mnh nng 70 kg sn xut khong 3 g khng th mi ngy. Khong 2/3 trong s ny l khng th c tn l IgA c sn xut bi t bo B trong thnh rut v ng h hp v sau chuyn vo lp dch nim mc ca nhng ni ny. Mt lng ln IgA c sn xut chng t cc c quan ny c b mt nim mc rt ln. Sau khi tip xc vi mt khng nguyn no , p ng to khng th ban u a s xy ra cc m lymph, ch yu l lch, hch bch huyt v m lymph nim mc; nhng nhng t bo to ra khng th lu di th c th nm cc m khc, nht l ty xng. Nhng khng th i vo tun hon th c thi gian na i sng rt ngn. Loi khng th c nhiu nht trong huyt thanh l IgG ch c thi gian na i sng l 3 tun.

3.2. Cu trc phn t ca khng th Cc nghin cu trc y v khng th ch yu l ly khng th t mu cc c th c gy min dch ri sau tinh ch kho st. Nhng cch ny th khng th dng xc nh cu trc ca khng th mt cch chnh xc, bi v huyt thanh cha qu nhiu loi khng th c sn xut bi nhiu cln t bo B p ng vi nhiu quyt nh khng nguyn (epitp) khc nhau (v c gi l khng th a cln). C hai pht hin t ph to iu kin c th kho st cu trc khng th mt cch chnh xc. Pht hin th nht l bnh nhn a u ty c mt khi u tng bo tit ra khng th n cln vi lng ln trong mu v nc tiu c th xc nh tnh cht ha sinh ca chng. Pht hin th hai, quan trng hn, l k thut to ra khng th n cln c Georges Kohler v Cesar Milstein m t nm 1975. H tm c cch lm cho t bo sn xut khng th bt t bng k thut to u lai (hybridoma); nhng u lai ny cho php sn xut khng th chng li ch mt tnh c hiu khng nguyn nh trc. Vic to ra c qun th t bo sn xut khng th thun nht ny gip cho cc nh nghin cu xc nh c trnh t acid amin ca tng phn t khng th. 3.2.1. c im chung ca cu trc khng th Cc glycoprotein huyt tng hoc huyt thanh trc y thng c phn chia theo tnh cht ha tan ca chng thnh albumin v globulin v phn

chia su hn da theo tnh in di ca chng. Hu ht khng th c tm thy trong thnh phn in di nhanh th ba ca globulin v c gi l gamma globulin (gamma l ch ci th ba trong mu t Hy Lp). Mt tn thng gi na ca khng th l immunoglobulin (globulin min dch), vit tt l Ig. Trong quyn sch ny hai thut ng immunoglobulin v khng th thng c dng vi cng mt ngha. Tt c mi phn t khng th u c chung mt cu trc c bn ging nhau, v s khc bit ch thy v tr kt hp khng nguyn. S khc bit ca vng kt hp khng nguyn gip cho khng th lin kt d dng vi khng nguyn v mt cu trc. Trong mi c th c khong t 107 n 109 phn t khng th khc nhau mang nhng vng kt hp khng nguyn khc nhau. Cc chc nng hiu qu v tnh cht ha l ca khng th thng do phn khng lin quan n khng nguyn m trch v nhng phn ny thng khng khc nhau my gia cc khng th. Mi phn t khng th c mt cu trc li i xng c cu to bi hai chui nng v hai chui nh ging ht nhau (Hnh 3.1). Mi chui nh c trng lng phn t khong 24 kD, v mi chui nng khong 55-70 kD. Mt chui nh c lin kt ng ha tr vi mt chui nng bng mt cu disulphua v cc chui nng cng ni vi nhau bng nhng cu disulphua. C chui nh v nng u cha nhng chui n v ng nht v lp i lp li. Mi n v c di 110 acid amin cun li mt cch c lp thnh nhng bi gi l lnh vc Ig (Ig domain). Mt lnh vc Ig cha hai tm gp b, mi lp c 3-5 chui polypeptid. C nhiu protein quan trng khc trong h thng min dch cng cha nhng lnh vc c cu to m-tp tm gp tng t nh vy v c cc chui acid amin ging nh Ig. Tt c nhng phn t cha cu to theo m-tp ny c t chung mt tn l siu h Ig (Ig superfamily), v tt c nhng gen m ha cho cc lnh vc Ig ca nhng phn t ny c cho l u tin ha t mt gen t tin.

Hnh 3.1. Cu trc ca mt phn t khng th A. S cu trc ca mt phn t IgG. Din kt hp khng nguyn c to bi lnh vc thay i ca chui nh (VL) v chui nng (VH) nm cnh nhau. Cc vng C ca chui nng tn cng ti phn ui. B. S cu trc ca phn t IgM gn trn mng t bo lymph B. IgM c nhiu hn IgG mt lnh vc vng C chui nng (CH) v tn cng bng mt on C cm xuyn qua mng t bo. C. Cu trc ca IgG ngi c v nh php chp tinh th bng tia X. Trong s ny chui nng c v bng mu xanh nc bin v , cn chui nh c mu lc.

C chui nng v nh u mang mt u tn cng amin lun thay i (gi l vng bin i hay vng V) tham gia vo vic nhn din khng nguyn v mt u tn cng cacboxyl hng nh (gi l vng hng nh hay vng C); vng hng nh ca chui nng lm trung gian cho cc chc nng hiu qu. Trn chui nng, vng V ch c 1 lnh vc Ig, nhng vng C th c 3-4 lnh vc Ig. Mi chui nh ch cu to bi 1 lnh vc Ig vng V v 1 lnh vc Ig vng C. Vng bin i ca mi phn t khng th gip phn bit khng th

c sn xut bi mt cln t bo B ny vi khng th c sn xut bi mt cln t bo B khc. Vng bin i ca chui nng (c gi l VH) nm st bn cnh vng V ca chui nh (c gi l VL) to nn din kt hp khng nguyn (Hnh 3.1). Bi v n v cu to c bn ca mi phn t khng th cha 2 chui nng v 2 chui nh nn n c 2 din kt hp khng nguyn. Cc lnh vc ca vng C tch bit vi din kt hp khng nguyn v khng tham gia vo qu trnh nhn din khng nguyn. Cc vng C ca chui nng c kh nng tng tc vi cc phn t v t bo hiu qu khc ca h min dch nn do m trch hu ht cc chc nng sinh hc ca khng th. Ngoai ra, u tn cng cacboxyl ca cc chui nng c tc dng gn cc phn t khng th mng vo mng t bo B. Vng C ca chui nh khng tham gia vo cc chc nng hiu qu v cng khng dnh vo mng t bo. 3.2.2. c im cu trc ca vng bin i v mi lin quan vi s lin kt khng nguyn Mi mt khng th thng mang 3 on ngn acid amin vng V (ca c chui nng v chui nh) rt ring cho khng th v c gi l vng siu bin. Nhng vng siu bin ny c di khong 10 acid amin v c gi yn ti v tr ca n chui peptid to nn lnh vc ca vng V. Trong mi phn t khng th, 3 vng siu bin ca vng VL v 3 vng siu bin ca vng VH c ko li vi nhau to nn mt cu trc khng gian ba chiu, l din kt hp khng nguyn. Bi v cu to ny c to ra sao cho khp vi cu trc khng gian ba chiu ca phn t khng nguyn tng ng nn nhng vng siu bin ny cn c gi l vng xc nh tnh b khuyt (complementarity-determined regions, CDR). Trn mi chui acid amin ca VL hoc VH, cc vng ny c t tn l CDR1, CDR2 v CDR3. Vng CDR3 ca c VL v HL l vng c bin i cao nht trong s 3 vng va k. C nhng c ch di truyn to ra tnh a dng cao hn CDR3 so vi CDR1 v CDR2. Nghin cu hnh nh tinh th ca khng th cho thy cc CDR to ra nhng cung ha hc a ra b ngoi khng th sn sng tng tc vi khng nguyn. S khc bit v trnh t acid amin trong cc CDR ca cc phn t khng th khc nhau to ra cu trc ha hc ring bit cho chng v c th hin ra b mt ca khng th to nn tnh c hiu i vi khng nguyn. 3.2.3. c im cu trc ca vng hng nh v mi lin quan vi chc nng hiu qu Cc phn t khng th c th c chia thnh nhiu lp khc nhau da trn s khc bit v cu trc vng C ca chui nng. Cc lp khng th cn

c gi l isotyp v gm c 5 lp c t tn l: IgA, IgD, IgE, IgG, v IgM. ngi, cc isotyp IgA v IgG c th c chia thnh cc tiu lp v t tn l: IgA1, IgA2, IgG1, IgG2, IgG3, IgG4. ( chut nht, loi ng vt thng c dng trong nghin cu min dch hc, th lp IgG c chia thnh cc tiu lp IgG1, IgG2a, IgG2b, v IgG3.) Vng C ca chui nng ca tt c cc phn t khng th trong mt lp hoc tiu lp u c chung mt trnh t acid amin. Trnh t ny khc vi trnh t ca lp khc hay tiu lp khc. Cc chui nng c t tn theo ch ci Hy Lp tng ng vi isotyp khng th: IgA1 cha chui nng a1; IgA2 cha a2; IgD cha d; IgE cha e; IgG1 cha g1; IgG2 cha g2; IgG3 cha g3; IgG4 cha g4 v IgM cha m. Trong khng th ca IgM v IgE ngi, vng C cha 4 lnh vc Ig ni tip nhau. Vng C ca IgG, IgA, v IgD ch cha 3 lnh vc Ig. Nhng lnh vc ny c k hiu l CH v c nh s t u tn cng amin n u tn cng cacboxyl (v d CH1, CH2, .v.v.). Trong mi isotyp, cc vng ny c k hiu c th hn (v d Cg1, Cg2 trong IgG). Khng th c th c tc dng nh mt khng nguyn khi n c a vo mt c th l v kch thch c th to khng - khng th. Bng cch gy min dch mt con vt bng khng th ly t mt con vt khc loi, chng ta c th sn xut ra cc khng - khng th c hiu cho mt lp hoc tiu lp Ig, v khng th kiu ny thng c dng thng xuyn trong cc nghin cu lm sng hoc thc nghim v p ng min dch dch th. Nhng lp v tiu lp khng th khc nhau s to nn nhng chc nng hiu qu khc nhau. Nguyn nhn l v hu ht cc chc nng hiu qu u qua trung gian ca s kt hp vng C chui nng vo th th ca n ln cc loi t bo nh i thc bo, t bo NK, t bo mast, hoc kt hp vi cc loi protein huyt tng khc nhau nh protein b th. Cc lp v tiu lp khng th khc nhau vng C nn cng khc nhau v chc nng hiu qu. Chui nh ca khng th c hai lp v c gi l k v l phn bit nh vng hng nh tn cng bng cacboxyl. Mt phn t khng th c th c hoc l 2 chui nh k hoc l 2 chui nh l, v khng bao gi c mi loi mt chui. Trnh t acid amin ca vng C chui nh k (Ck) khc vi trnh t ca vng C chui nh l (Cl), nhng trnh t Ck ca tt c cc phn t khng th u ging ht nhau, v trnh t Cl cng vy. Mc d c khc nhau v trnh t acid amin nhng Ck v Cl hon ton ng nht v mt cu trc, v u gp vo trong cng mt lnh vc Ig. ngi, khong 60% phn t khng th c chui nh k v 40% c chui l. Ngi ta tm thy t l ny thay i rt r trn bnh nhn u t bo B n cln bi v cc cln t bo ung th sn xut nhng phn t khng th vi cng mt lp chui nh m thi. V ngi ta dng t l t bo mang k v t bo mang l chn on u lymph t bo

B. chut, lng khng th cha k nhiu gp 10 ln lng khng th cha l. Khc vi lp chui nng, cc lp chui nh khng to ra iu g khc nhau v chc nng ca khng th. Khng th c th xut hin di dng cht tit (dng tit) hoc nm trn mng t bo (dng mng). Dng khng th ny khc vi khng th huyt thanh v trnh t acid amin u tn cng cacboxyl ca vng C chui nng. Dng tit gp trong mu v cc dch ngoi bo. i vi dng ny, trnh t acid amin ca vng CH c tn cng bng cc acid amin a nc v tch in. y l cu trc c trng cho cc protein gn trn mng t bo. Cc khng th IgG v IgE c tit ra di dng n phn t tc dng n v khng th c bn (bao gm 2 chui nng v 2 chui nh). Ngc li, cc khng th IgM v IgA th thng to nn nhng phc hp a phn t tc bao gm t 4 chui nng v 4 chui nh tr ln. Cc khng th a phn t IgM v IgA cn cha mt polypeptid ph vi trng lng phn t 15 kD gi l chui J (lin kt), gn vi cc phn t khng th bi cc cu ni disulphua v c chc nng lm bn vng cc phc hp a phn t ny. 3.2.4. S tng hp v biu hin ca phn t Ig Cc chui nng v nh ca Ig c tng hp trong cc ribosom nm trn b mt ca h li ni bo. S kt hp ng ha tr ca cc chui nng v cc chui nh c thc hin nh cc cu ni disulphua v cng xy ra trong h li ni bo. Sau khi c hnh thnh phn t Ig c chuyn n th Golgi t chuyn ra mng t bo trong cc nang nh v sau c tit ra khi t bo qua mt qu trnh gi l thot bo (exocytosis). Cc protein khc cn gn vo Ig nh cc chui J cng ng thi c thc hin trc khi bi tit ra khi t bo. Trong nhng t bo sn xut khng th lp IgA v IgM th s sao chp ca gen chui nng v gen chui nh c thc hin ng thi vi s sao chp gen chui J. S trng thnh ca cc t bo B trong ty xng thng i km vi s thay i biu hin gen Ig dn n sn xut cc phn t Ig di cc dng khc nhau (Hnh 3.2). Cc t bo sm nht ca dng lymph B c gi l t bo tin B sn xut ra cc dng mng ca chui nng m, nhng a s cc protein li trong bo tng. Hu ht cc chui nng m ni bo trong t bo tin B u t phn hy ngay trong t bo. Ch mt lng nh cc phn t ny c biu hin mng t bo v kt hp vi nhng protein c tn l chui nh thay th to nn th th ca t bo tin B. Cc t bo B trng thnh hoc cha trng thnh u sn xut cc chui nh k hoc l lin kt vi

chui nng m to nn phn t IgM. S t hp ny bo v cho chui nng khi b phn hy trong ni bo v cho php IgM biu hin trn b mt t bo. T bo B trng thnh c biu hin ca IgM v IgD trn b mt. Cc th th Ig mng ny c chc nng nhn din khng nguyn v khi ng qu trnh hot ha t bo B. Th th khng nguyn ca t bo B lin kt khng ng ha tr vi hai protein mng khc l Iga v Igb to nn cc phc hp phn t v iu ny rt cn i vi vic th hin IgM v IgD b mt. Khi t bo B c khng nguyn hoc cc kch thch khc hot ha, chng bit ha thnh cc t bo sn xut khng th. Qu trnh ny thng phi hp vi s bin i cc th dng sn xut Ig. Mt trong nhng bin i l s chuyn t Ig mng sang Ig tit. Mt bin i th hai l xut hin cc biu hin khc ca isotyp chui nng ngoi IgM v IgD. Qu trnh ny gi l chuyn mch isotyp chui nng.

Hnh 3.2. S bc l Ig trong qu trnh trng thnh t bo B Cc giai on trng thnh t bo B thng i km vi cc bin i trong sn xut chui nng v chui nh ca Ig. 3.3. S kt hp khng nguyn khng th 3.3.1. Cc c im lin quan n qu trnh nhn din khng nguyn Phn t khng th c nhiu c im cu trc rt quan trng i vi qu trnh nhn din khng nguyn cng nh thc hin chc nng hiu qu. Cc c im ny nm ch yu vng V ca phn t khng th. 3.3.1.1. Tnh c hiu (specificity)

Khng th bao gi cng kt hp rt c hiu cho khng nguyn tng ng ca mnh. Ch cn mt khc bit nh v cu trc ha hc l c th lm cho s kt hp khng nguyn-khng th b tr ngi. Tnh c hiu tinh t ca phn t khng th hin din trn tt c cc lp phn t. V d, khng th c th phn bit hai quyt nh khng nguyn khc nhau ch mt v tr acid amin c th hin rt t trn cu trc cp hai. Bi v cu to sinh ha ca tt c sinh vt sng u c bn l tng t nhau, nn tnh c hiu cao ny rt cn khng th to c p ng vi mt khng nguyn ca mt vi khun m khng to p ng vi phn t c cu trc tng t ca c th mnh hay ca vi khun khc. Tuy vy, cng c trng hp mt s khng th c sn xut chng li mt khng nguyn li c th lin kt vi mt khng nguyn khc c cu trc lin quan. iu ny c gi l phn ng cho. Khng th c to ra chng vi khun i khi li cho phn ng cho vi t khng nguyn ca c th mnh v c th gy ra mt s bnh l min dch. 3.3.1.2. Tnh a dng (diversity) Nh trnh by phn trc, mt c th c kh nng to ra mt s lng ln (n 109) khng th c tnh c hiu khc nhau. S hin din ca lng ln khng th vi tnh c hiu khc nhau ny c gi l tnh a dng ca khng th v ton b su tp khng th vi tnh c hiu khc nhau ny c gi l h cha (repertoire) khng th. C ch di truyn ca tnh a dng ny nm t bo lymph. Chng c thc hin trn c s s ti t hp ngu nhin ca mt s b trnh t DNA di truyn vo cc gen chc nng m ha cho vng V ca chui nng v chui nh. Mt c s khc ca tnh a dng l s thm ngu nhin cc trnh t nucleotide khng theo khun mu vo cc gen on V. Hng triu dng cu trc khc nhau tp trung ch yu vo vng siu bin ca c chui nng v chui nh to nn tnh c hiu i vi khng nguyn. 3.3.1.3. i lc (affinitive) v i tnh (avidity) Kh nng trung ha c t v vi sinh vt ca khng th lun ph thuc vo s gn kt cht ch ca chng vo khng th. S gn kt ny c c l do i lc v i tnh cao ca s tng tc. C ch to ra i lc cao ca khng th l do nhng bin i tinh vi ti vng V ca phn t khng th trong giai on p ng dch th. Nhng bin i ny c to ra do qu trnh t bin thn ca t bo lymph B sau khi c khng nguyn kch thch. Kt qu l

hnh thnh nhng cu trc mi ca lnh vc V, trong s c nhng cu trc gn kt c i lc cao hn nhiu so vi cu trc ban u ca cc lnh vc V (Hnh 3.3). Nhng t bo B sn xut khng th c i lc cao rt d c khng nguyn kch thch v tr nn t bo B ch o i vi nhng ln tip xc khng nguyn v sau. Qu trnh ny c gi l s trng thnh v i lc c kh nng lm tng dn i lc trung bnh ca khng th i vi khng nguyn trong vic to ra p ng dch th. V d, nu mt khng th trong p ng min dch tin pht i vi mt khng nguyn c h s i lc lin kt Kd l 10-7 n 10-9 M th trong p ng th pht i vi khng nguyn i lc s gia tng v h s Kd by gi s l 11-11 M hay thm ch nh hn.

3.3.2. Cc c im lin quan n chc nng hiu qu Cc chc nng hiu qu ca khng th thng lin quan n on Fc ca phn t khng th, do nhng isotyp khc nhau on Fc s to ra chc nng hiu qu khc nhau. V d, phn t IgG thng gn vi t bo vi khun chuyn vi khun n cho t bo trung tnh hoc i thc bo tiu dit. iu ny thc hin c l nh phn t IgG c gn khng nguyn nh c on Fc m c th lin kt vi chui nng g ca mnh vi phn t th th c hiu cho on Fc nm trn b mt ca t bo trung tnh v i thc bo. Ngc li, phn t IgE gn vo c th giun trn chuyn chng n cho t bo i toan tiu dit v trn t bo ny c nhiu th th c hiu dnh cho IgE. Mt c ch hiu qu khc ph thuc Fc trong min dch dch th l s hot ha h thng b th theo con ng c in. H thng b th to ra cc ha cht trung gian ca phn ng vim v thc y qu trnh thc bo cng nh ly gii t bo ch. Qu trnh ny c bt u vi s lin kt ca mt protein b th c tn l C1q vo on Fc ca phn t khng th IgG hoc IgM trong phc hp khng nguyn khng th. FcR v v tr kt hp b th ca khng th u nm khu vc C ca chui nng ca tt c cc isotyp. Tt c cc hiu qu chc nng ca khng th u ch c thc hin khi khng th lin kt vi khng nguyn ch khng phi dng Ig t do. Nguyn nhn l cn phi c t nht 2 on Fc nm k cn nhau c th tc ng vo cc h thng hiu qu nh cc protein b th v FcR ca ai thc bo. Yu cu phi c nhng phn t lin k ny m bo cho chc nng hiu qu c thc hin mt cch c hiu n ng khng nguyn ch v loi b chng v cng l nhm lm cho cc khng th lu ng t do trong mu

khng tc ng tha vo h thng hiu qu.

Hnh 3.3. Cc thay i ca cu trc khng th trong qu trnh p ng min dch dch th Trong qu trnh trng thnh i lc, t bin c th xy ra vng V dn n thay i tnh c hiu trong khi chc nng hiu qu ph thuc vng C khng thay i g. T bo B hot ha c th chuyn cc phn t Ig mng sang Ig tit. Ig tit c th c t bin gen hoc khng. Trong qu trnh chuyn mch isotyp, c bin i vng C trong khi vng V khng c g thay i. Vic chuyn mch isotyp c th gp c Ig mng ln Ig tit. S thay i ca isotyp khng th trong qu trnh p ng dch th s nh hng vic p ng min dch hot ng loi b khng nguyn ni no v u. Sau khi c khng nguyn kch thch, mt cln t bo B s sn xut

khng th vi cc isotyp khc nhau nhng c cng lnh vc V tc la c hiu cng 1 khng nguyn. Cc t bo B cha tip xc khng nguyn s ng thi sn xut IgM v IgD c tc dng nh l th th b mt i vi khng nguyn. Khi t bo B tip xc vi mt vi khun chng hn th trong t bo s xy ra mt qu trnh gi l chuyn mch isotyp (isotype switching) trong typ ca vng CH do t bo B sn xut b chuyn i nhng cn vng V v tnh c hiu th khng thay i (Hnh 3.3). V qu trnh chuyn mch isotyp m cc t bo tin thn ca t bo B sn xut IgD v IgM sn xut c cc isotyp khc c kh nng tiu dit khng nguyn tt hn. V d, khng th chng vi khun v virus ch yu l typ IgG l typ c xu hng thc y qu trnh thc bo vi khun, cn typ chuyn i ph vi giun trn th ch yu l IgE l typ c kh nng ph hy k sinh trng ny. Vng C trn chui nng ca khng th cng quyt nh v tr phn b ca phn t khng th cc m. IgA thng l isotyp duy nht c th c bi tit qua lp thng b ca nim mc v do IgA l lp khng th ch yu ca cc dch tit k c sa. Tr s sinh c bo v khi cc bnh nhim trng nh khng th IgG c truyn t m sang trong qu trnh mang thai v trong giai on sm ca thi k b m. S truyn ny c thc hin qua trung gian ca mt th th Fc c bit c trong bnh nhau (gip khng th i vo tun hon phi) v trong ng tiu ha ca tr s sinh (gip hp th khng th t sa m). KHNG NGUYN 4.1. Cc tnh cht ca khng nguyn p ng to khng nguyn nh ta bit s xy ra khi c mt vt l t nhp vo c th v tip xc vi h thng min dch. Vt l c gi l cht gy khng th (antibody generator) hay khng nguyn (antigen). Tuy nhin, khng phi vt l no vo c th cng c tnh cht khng nguyn. Khng nguyn c hai tnh cht sau: (1) kch thch c c th to ra p ng min dch, tnh cht ny gi l tnh sinh min dch, v (2) c kh nng kt hp c hiu vi khng th tng ng, tnh cht ny l tnh c hiu. 4.1.1. Tnh sinh min dch Tnh sinh min dch ca mt khng nguyn ph thuc vo cc yu t sau:

(1) Tnh l ca khng nguyn: Khng nguyn cng l bao nhiu th kh nng kch thch to khng th cng mnh by nhiu. Tuy nhin, cn lu rng, trong mt s trng hp bnh l th thnh phn ca chnh bn thn c th cng c th gy ra p ng khng th chng li n, ta gi nhng thnh phn ny l t khng nguyn. (2) Cu trc ha hc ca khng nguyn: Cc khng nguyn thuc loi protein v polysaccharid c tnh sinh min dch cao. Khng nguyn cng phc tp v cu trc ha hc bao nhiu th tnh sinh min dch cng mnh by nhiu. Trn cu trc c nhng cu to chu trch nhim chnh trong vic kch thch to khng th, l cc quyt nh khng nguyn hay epitop. (3) Cch gy min dch v liu khng nguyn: Hu ht cc khng nguyn hu hnh (vi khun, hng cu, cc polymer ln,) khi a vo c th bng ng tnh mch u d dng gy p ng to khng th. Trong khi , c mt s phn t cn phi km thm mt cht h tr khc mi gy c p ng tt, ta gi cht h tr l t cht adjuvant. Loi t cht thng dng l t cht Freund, l mt hn dch vi khun lao cht trn trong nc v du. (4) S di truyn kh nng p ng ca c th: cng mt khng nguyn nhng cc c th khc nhau th to ra cc p ng min dch mc khc nhau. V th m Landsteiner phn bit hai khi nim: Tnh khng nguyn v tnh min dch, trong : Tnh sinh min dch = tnh khng nguyn + kh nng p ng ca c th. 4.1.2. Tnh c hiu Tnh c hiu ca mi p ng min dch c c l do mi khng nguyn c mt cu trc ring. Tnh c hiu ca khng nguyn khng phi do ton b phn t khng nguyn quyt nh, m do mt hoc nhiu on nh nm trn phn t khng nguyn quyt nh. Nhng on nh ny cc l quyt nh khng nguyn hay epitop. Epitop c hai chc nng, mt l kch thch c th to ra p ng min dch c hiu vi khng nguyn , v hai l lm v tr khng th hoc t bo lympho mn cm c th gn vo mt cch c hiu. Mt khng nguyn protein phc tp c th nhiu quyt nh khng

nguyn khc nhau, do m n c th kch thch to ra nhiu loi khng th khc nhau cng mt lc. Ty theo khng nguyn c th phn ng cng mt lc vi mt hay nhiu khng huyt thanh cha khng th do n to ra m ngi ta gi l khng nguyn n gi hay khng nguyn a gi. Trong cc phn ng huyt thanh hc ch c nhng khng nguyn a gi mi c th to ra mng li kt ta hoc ngng kt. 4.1.3. Phn ng cho Phn t khng th c tnh c hiu rt cao, nhng cng c trng hp khng th ca khng nguyn A li tc dng vi khng nguyn B, ta gi l phn ng cho. Nguyn nhn ca phn ng cho c th l do trn hai khng nguyn ny c hai epitop ging nhau hoc t nht l cng tng t nhau Trong thc nghim chng ta c th loi tr c phn ng cho bng phng php cho hp th. V d, ta bit khng huyt thanh khng A thng cho phn ng cho vi khng nguyn B cho nn khi lm phn ng tm khng nguyn A th kt ta d sai lc do tm nhm c B. Nh vy, trc khi tm A ta cho khng nguyn huyt thanh khng A vi khng nguyn B, nhng phn t no cho phn ng cho s to phc hp vi B. Sau khi ly tm loi phc hp ta s cn khng huyt thanh A khng cn phn ng cho vi B. 4.1.4. Hapten Hapten hay bn khng nguyn l mt khng nguyn khng ton nng, c trng lng phn t thp, khng c tnh sinh min dch nhng c tnh c hiu khng nguyn. Khi hapten c gn vi mt cht protein ti thnh mt phc hp th phc hp ny c tnh sinh min dch. Ni r hn, trong thc nghim, nu ta ch a hapten vo c th th khng c p ng min dch c hiu xy ra, nhng nu ta a phc hp protein-hapten vo th c th s p ng bng cch sn xut khng th chng li c hapten ln protein (Hnh 4.1). Khng th chng hapten do phc hp kch thch to ra c th phn ng c vi hapten t do. Trong trng hp ny, ta c th xem hapten nh l mt quyt nh khng nguyn c thm vo bn cnh nhng quyt nh khng nguyn khc c mt trn phn t protein. Trong s cc hapten th nhm dinitrophenyl v nhm azobenzenarsenat l hay c dng trong thc nghim. Nhm dinitrophenyl c th gn vo nhm NH2 ca lysine v nhm azobenzenarsenat c th gn vo gc tyrosin. Mt trng hp khc ta cn lu , c khi ch cn a hapten vo c th l c th gy p ng min dch (loi hapten thng dng nht cho th nghim kiu ny l DNCB,

dinitrochlorobenzen). L do l v hapten ny khi vo c th th gn vi protein ca c th tr thnh phc hp protein hapten c tnh sinh min dch.

Hnh 4.1. S minh ha p ng vi hapten Bn thn hapten khng to ra p ng, nhng khi c lin kt in vitro v/hoc in vivo vi cng hp protein th s to ra khng th phn ng c vi hapten v vi cng hp protein .

4.2. Mt s khng nguyn quan trng 4.2.1. H khng nguyn nhm mu ABO H ny bao gm 4 nhm mu khc nhau: A, B, AB v O. K hiu nhm mu biu th khng nguyn c mt trn b mt hng cu. C th nhm mu A th c khng nguyn A, nhm B th c khng nguyn B, nhm AB c khng nguyn A v B v nhm O th khng c c A v B trn hng cu. Mt c im khc ca c th l ngi mu A c mang khng th chng B trong huyt thanh, ngi mu B th c huyt thanh chng A, ngi AB th huyt thanh khng c khng th chng hai khng nguyn ny cn nhm O th c c hai loi khng th. Cc khng nguyn thuc h ABO do mt locus gen kim sot vi ba allel A, B, v O, trong A v B tri hn O. Tnh c hiu khng nguyn nhm mu trong h ABO c quyt nh bi s c mt ca mt s gc ose trong phn polysaccharid. Cc khng nguyn ny u c chung mt li sphingolipid- polysaccharid. Nu li ny c gn thm gc fucose th xut hin cht H. Cht ny c trn b mt hng cu ca hu ht cc c th v l nn sut hin khng nguyn A v khng nguyn B. Nu ti v tr galactose cui cng ca cht H c gn thm N-acetyl galactosamin th xut hin khng nguyn A. Cn nu gn thm mt galactose na th xut hin khng nguyn B (Hnh 4.2).

Hnh 4.2. S cu to khng nguyn ABO

Cc gen A hoc B m ha cho enzym transferase gn N-acetylgalactosamin hoc galactose vo cht H to nn nhm mu A hoc B. Nu khng c gen A hoc B th mu thuc nhm O. V mt di truyn, tham gia vo s hnh thnh khng nguyn nhm mu c hai h gen, l h Hh i vi cht H v h ABO. Hai h ny hot ng c lp vi nhau. i a s chng ta c gen H, nhng cng c ngi khng c (c th ng hp t hh). Nhng ngi ny d c gen ca h ABO nhng trn hng cu vn khng c khng nguyn A hoc B nn c ghi nhn l nhm O nhng khi truyn mu O thc s vo ngi ny (tc a cht H vo cho ngi khng c H) th c th gy tai bin truyn mu. Nhm c bit ny c gi l nhm O Bombay. 4.2.2. H khng nguyn nhm mu Rh Nm 1930, Landsteinner v Wiener pht hin ra nhm mu Rh. H gi nhng ngi c hng cu ngng kt vi huyt thanh th khng hng cu ca kh Rhessus l ngi Rh+, s ngi cn li l Rh-. Nhng ri sau ny, ngi ta pht hin ra rng, khng nguyn trong h Rh khng n gin nh vy. H Rh c nhiu khng nguyn, phn ln c tnh sinh min dch yu v hay gy phn ng cho. Ch c khng nguyn D l c tnh sinh min dch mnh. Khi hng cu c khng nguyn D th c gi l Rh+ m khng cn n cc khng nguyn khc trong h ny. Khng th khng D khng xut hin t nhim trong mu nh cc khng th ca h ABO. V khng nguyn Rh phn b tha tht trn hng cu nn thng kh gy ngng kt hng cu khi lm phn ng xc nh nhm mu Rh, v th ngi ta phi dng n th nghim Coombs gim tip (Hnh 4.3)

Hnh 4.3. Phn ng Coombs gin tip (a). Hnh nh phn ng m tnh; (b) Hnh nh phn ng dng tnh; (c) C ch phn ng trong trng hp bt ng nhm mu Rh. 4.2.3. Khng nguyn vi sinh vt Khng nguyn vi sinh vt l loi khng nguyn rt phc tp: khng nguyn v, khng nguyn thn, khng nguyn lng, khng nguyn ngoi t bo, v.v V khng nguyn v th khng nguyn v ca ph cu thng hay c nghin cu nhiu nht. Khng nguyn ny thuc loi polysaccaride, c ti 80 typ huyt thanh khc nhau. V khng nguyn thn th cc vi khun rut non, lp ngoi ca vch vi khun c mt lipopolisaccharide: phn lipid c tnh c, cn phn polysaccharid th c tnh khng nguyn v y chnh l khng nguyn thn (cn gi l khng nguyn O). Salmonella c n hn 60 khng nguyn O m cu trc c hai phn: phn nhn c bn v phn chui ngang. Phn nhn ging nhau tt c cc Salmonella. Phn chui ngang gm nhng tiu n v oligosaccharide sp xp lp i lp li. Chnh cc chui ngang quyt nh tnh c hiu ca mi nhm Salmonella. Cc khng nguyn lng ca Salmonella c bn cht l protein, cn c gi l khng th H, quyt nh tnh c hiu ca mi typ Salmonella. Ngi ta pht hin Salmonella c hn 1000 typ huyt thanh khc nhau.

Cc khng nguyn ngoi t bo nh c t v cc enzym cng c bn cht protein. Mt loi khng nguyn ngoi t bo ca lin cu l Streptolysin O thng c dng trong chn on huyt thanh. Cc vi khun trong bch hu, un vn c ngoi c t gy bnh v cc vaccin phng cc bnh ny y l c t c gii c. Khng th virus c th trn b mt ht virus (capsid) hoc bn trong. Ty theo tnh c hiu, c th phn bit cc khng nguyn nhm, cc khng nguyn typ v khng nguyn typ ph. Trong cc khng nguyn nhm, c th k lm v d khng nguyn nucleoprotein (NPA), l khng nguyn typ, chng hn trong bnh bi lit, cho php phn bit ba typ virus bi lit khc nhau. Trong trng hp virus cm, ngoi vic phn bit ba typ A, B, C, ngi ta cn phn bit typ ph na. Cc typ ph ca A v B l kt qu ca nhng bin i ca khng nguyn b mt. 4.2.4. Khng nguyn ha hp m T lu, ngi ta bit rng, vic truyn mu s d thnh cng l nh, s ph hp gia mu ca ngi cho v mu ca ngi nhn. Trong bi pht biu khi nhn gii Nobel vo nm 1931, Ladsteiner cho rng c l c nhng nhm ging nhm mu lin quan n vic chp nhn hoc thi b nhng m ghp khc. tng ny dn dt Gorer i n vic xc nh mt nhm khng nguyn chut m khi nhm khng nguyn ny ging nhau gia con cho v con nhn th mnh ghp c thi gian sng lu hn. Tn gi khng nguyn ha hp m c dng ch khng nguyn tham gia vo vic thi ghp ny. Ngi ta cng nhn thy rng ph trch m ha cc khng nguyn ny l mt vng c bit ca genom v ta gi vng ny l Phc h ha hp m ch yu (Major Histocompatibility Complex, MHC); chut nht n mang tn l vng H-2, v nm trn nhim sc th 17. Nhng h thng tng ng vi phc h ha hp m ch yu chut cng pht hin c trn tt c cc ng vt c v khc. ngi, phc h ha hp m ch yu l cm gen HLA trn nhim sc th s 6. S ti t hp gia cc cc ca phc h gen xy ra khong 1% cc gia nh, nh c th tnh c rng HLA chim khong 1/3.000 trong ton b genom. iu ny c ngha rng c th c hng trm gen nm trong cm HLA ny. Mc d MHC

ln u tin c pht hin nh vai tr ca n trong thi ghp, nhng ngy nay ngi ta bit rng, cc protein sn phm ca on gen ny tham gia vo nhiu cng on trong nhn din min dch, bao gm tng tc gia cc t bo lympho khc nhau cng nh cc lympho bo vi t bo trnh din khng nguyn. 4.2.4.1. S sp xp cc gen MHC Ngi ta xc nh c phc hp gen MHC mang nhiu gen ring l; v mc d phc hp c chc nng chung, tng i ging nhau gia cc loi, nhng chi tit v phn b th mi loi mi khc. Gn y, ngi ta thit lp c bn gen hon chnh cho MHC chut nht. Nh m chng ta bit c rng locus no th chu trch nhim m ha cho on polypeptid no. Ch cn iu vng mc l cch thc cc polypeptid v protein thc hin chc nng ca mnh nh th no cho ph hp vi quy nh ca MHC m ha tm ra c l nh k thut min dch hc (dng khng th n cln), do m ngi ta thng gi cc protein ny l khng nguyn MHC. Cc protein ca MHC gm c 3 lp khc nhau v c cu trc ln chc nng: -Protein lp I (tc khng nguyn MHC lp I) gm c hai polypeptid. Peptid ln c m ha bi MHC, peptid ny lin kt vi mt polypeptid th hai l b2- microglobulin c m ha bi mt gen ngoi on MHC. -Cc protein lp II (tc khng nguyn MHC lp II) gm c hai peptid khng ng ha tr vi nhau c tn l chui a v chui b, c hai u l sn phm ca MHC. - Cc protein lp III (tc khng nguyn MHC lp II) l cc thnh phn b th c m ha bi MHC. Ngoi ra cn c nhng locus ph nm ngoi phc hp H-2 (phc hp TLA) tham gia m ha cho protein lp I v bi v nhng protein ny cng c chc nng min dch nn cng c a vo bn gen Hnh 4.4.

Hnh 4.4. S v tr cc gen MHC C 17 gen Qa trong vng Qa v 12 gen trong vng Tla mc d a s chng dng ngh. ngi, nhng vng chnh l D, B, C, v A. Cc vng A v B ngi l vng c chc nng tng ng vi vng K v D chut, iu c ngha rng nhng sn phm ca chng tc ng vi t cch l nhng phn t nhn din trn b mt t bo, v t bo T gy c s nhn din nhng phn t ny khi thc hin chc nng ca n. Vng D ca ngi tng ng vi vng I ca chut v sn phm ca chng (hai chui protein a v b) tham gia vo qu trnh hp tc ca t bo gia t bo ca h min dch. Cc sn phm vng I ca chut c gi l khng nguyn Ia. Tng ng vi khng nguyn DR, DP, v DQ ca ngi. Ngi ta nhn thy rng, cng ca p ng min dch trn chut c xc nh mt phn bi cc gen p ng min dch. 4.2.4.2. Phn b ca khng nguyn MHC ngi, tt c cc t bo c nhn u nht thit phi mang cc khng nguyn ca vng A, B, C, nhng cn khng nguyn c m ha bi vng D th ch phn b hn ch nhng t bo tng ng vi t bo chut c mang khng nguyn I. Khng nguyn lp I ch c trn t bo B, i thc bo, t bo mono v c l c t bo biu m. Ngoi ra, mt s khng nguyn lp I xut hin c trn t bo T c ch v khng nguyn lp II th c trn t bo T c hot ha (Bng 4.1). Bng 4.1. Phn b ca khng nguyn MHC cc m

Tiu MHC H-2 K, D, L I-A I-E I-J

vng Phn b ca khng nguyn ti cc m HLA A, B, Tt c t bo c nhn v tiu cu C Hng cu (chut) D Lymph B, i thc bo, T bo mn, T bo thng b (?), T bo u sc t, T bo T hot ha Lymph T c ch

4.2.4.3. Cu trc ca khng nguyn MHC Nhng cng trnh gn y nghin cu cc khng nguyn MHC ring bit gip lm sng t cu trc ca chng. Vi t cch l phn t tham gia vo tng tc t bo, khng nguyn MHC thng c tm thy trn mng t bo. Chng l nhng phn t glycoprtein cm vo mng t bo, do nghin cu c chng ta thng phi tch ri chng khi mng bng hai cch: - Hoc l dng cc cht ty (detergent) gii phng chng khi mng. - Hoc l dng enzym papain ct phn MHC nm thi ra khi b dy ca mng. Khi phn t ny c ct bng enzym th chng c khc vi khng nguyn MHC nguyn vn bi v chng mt phn cm su vo mng t bo. Ngi ta lm tinh khit khng nguyn ha tan bng cc k thut ha sinh kinh in nh sc k i tnh, dng lectin hoc khng huyt thanh. Ngi ta nhn thy rng tinh luyn khng nguyn MHC bng sc k i tnh trn ct khng th n cln c nhiu u im hn cc k thut ha sinh khc (Hnh 4.5). Mi khng nguyn lp I bao gm mt polypeptid c gn ng c trng lng phn t khong 45.000 lin kt khng ng ha tr vi mt peptid khng c ng (tc b2 -microglobulin, c trng lng phn t khong 12.000). D b2 - microglobulin khng tham gia vo b mt khng nguyn ca phn t HLA, nhng n cn cho qu trnh th hin ca lp I. Nu mt c th no thiu bm sinh b2 - microglobulin th quyt nh khng nguyn ca lp I khng th hin c.

Hnh 4.5. S minh ha cu trc cc phn t MHC lp I v II S cho thy cc phn t MHC lun c cu trc cm su vo mng t bo Cu trc ca lp II t c bit r hn lp I, chng gm hai chui poypeptid khc nhau a v b gn vi nhau bi lc ni khng ng ha tr, c hai chui u cm vo mng t bo. Chui ngn mang cc khng nguyn allotyp, v hai chui u c mang cc n v ng. Ngi ta bit nhiu v cu trc ca vng H-2I ca chut hn vng tng ng vi vng ny ngi l vng HLA-D. Trn chut, ngi ta pht hin thm nhng tiu vng ca H-2I, l tiu vng I-A v I-E. Kho st ring tng vng peptid v ca khng nguyn I-E chut cho thy rng, a s cc bin i cu trc ch xy ra chui b (trng hp khng nguyn HLA-D cng vy). 4.2.4.4. Chc nng ca khng nguyn MHC Cc khng nguyn MHC rt cn thit cho cc qu trnh nhn din min dch. Cc khng nguyn MHC khc nhau c nhn din bi nhng loi t bo T khc nhau. Nhng t bo T gy c tham gia vo vic nhn din v loi b cc t bo nhim virus v m ghp l c kh nng nhn din cc phn t H-2K v H-2D (tng ng HLA-A v HLA-B ngi) trn cc t bo l, v khi hp tc vi t bo T gip th s gy ph hy t bo l (Hnh 4.6)

a s t bo nhim virus th hin khng nguyn virus trn b mt ca chng, v nhng khng nguyn ny c nhn din bi t bo T gy c. ng thi ngi ta cng bit c rng t bo T gy c ch nhn din c khng nguyn virus khi c phi hp vi vic nhn din khng nguyn K-2K v -D c mt trn t bo b nhim. Bng cch ny t bo T gy c c th git cht t bo nhim. Nh vy, phn t H-2 trn b mt t bo nhim virus tc ng nh mt du hiu hng dn a t bo T gy c n tip cn bo ch, v gip n phn bit t bo ch vi cc t bo khc mang khng nguyn virus. Ngi ta vn cha bit r rng t bo gy c nhn din cng mt lc tnh c hiu virus v khng nguyn MHC t bo ch nh th no. C hai gi thuyt (c minh ha Hnh 4.7): - T bo gy c nhn din c lp hai khng nguyn ny. - S kt hp ca khng nguyn virus v khng nguyn MHC trn b mt t bo t bo lm bin i hnh dng cu trc ca phn t MHC, do m n nhn din nh mt thnh phn bn thn b bin i.

Hnh 4.7. Hai gi thuyt v vic t bo Tc nhn din khng nguyn virus v MHC trn b mt t bo ch. T bo Tc c th nhn din c lp cc phn t khng nguyn virus v MHC (gi thuyt 1) hoc nhn din chung phc hp to nn bi khng nguyn virus v MHC (gi thuyt 2)

Nhiu chc nng ca MHC khc s c cp c th hn, chng ta nghin cu cc b phn ca h thng min dch v MHC tham gia vo ht cc qu trnh nhn din min dch. Nhng hiu bit gn y cho thy rng, MHC v phn t khc tham gia v nhn din min dch ging nhau mt phn cu trc, v iu ny c l c lin quan v mt tin ha vi nhng phn t nhn din u tin trong thi k bo thai. C mt iu chng ta cn lu l c rt nhiu thay i allotyp xy ra cho cc khng nguyn MHC. S xut hin ca nhng tnh c hiu mi ca MHC c th thy nhng loi khc nhau v c lin quan vi nhau. Nguyn nhn ca s thay i ln ny cha c r. V tnh cht rt c th ca tng c th sinh vt m trong mt qun th khng c yu t bnh nguyn no c th gy bin i ging nhau cho ton b cc c th mc nhn din khng nguyn. Tuy vy, chng ta cn bit rng trong mt qun th c th c hin tng mt c th mang mt khng nguyn MHC c bit no th c tnh

d mc mt bnh tng ng hoc khng mc mt bnh tng ng so vi nhng ngi khc. l c im di truyn ca MHC. CC T BO CH YU CA H THNG MIN DCH

Hnh 5.1. Tm tt p ng min dch in vivo Khng nguyn c cc t bo c tua bt gi v tp trung vo hch lymph, chng hot ha cc t bo lymph. T bo T hiu qu v T nh c hnh thnh trong hch ri i vo tun hon c th n cc m ngoi bin. Khng th c sn xut trong c quan lymph v a vo mu c th tip cn khng nguyn bt c ni no. T bo nh cng i vo tun hon v c th dng chn trong c quan lymph hoc cc m khc. p ng min dch thu c pht trin qua nhiu bc lin tc nhau m

trong mi bc cn n tnh cht c bit khc nhau ca t bo v m min dch. Cc giai on ch yu ca nhng p ng ny v vai tr ca cc t bo v cc m khc nhau c trnh by Hnh 5.1. T bo tham gia vo p ng min dch thu c bao gm cc lymph bo c hiu khng nguyn, t bo trnh din khng nguyn v cc loi t bo hiu qu c chc nng loi b khng nguyn. Nhng t bo ny c gii thiu Chng 1, y chng ti m t hnh thi hc v c im chc nng ca lymph bo v t bo trnh din khng nguyn v gii thch nhng t bo ny c t chc th no trong cc m lymph. S lng ca mt s t bo c trnh by Bng 5.1. Mc d nhng t bo ny c tm thy trong mu nhng ni chng phn ng vi khng nguyn l ti m lymph hoc cc m khc. iu ny khng gy bin i g v s lng ca bch cu lu ng.

Bng 5.1. S lng bnh thng ca t bo bch cu mu

T bo bch cu - Trung tnh - i toan - i kim - Lymph - Mn

Tr trung bnh/1 microlit 7.400 4.400 200 40 2.500 300

Gii hn bnh thng 4.500 11.000 1.800 7.700 0 450 0 200 1.000 4.800 200 800

5.1. T bo lymph T bo lymph l loi t bo duy nht trong c th c kh nng nhn din mt cch c hiu v phn bit c cc quyt nh khng nguyn. Chng chu trch nhim v hai c im ca p ng min dch thu c, l tnh c hiu v tnh nh min dch. C nhiu bng chng c a ra chng minh cho vai tr ca lymph bo vi t cch l t bo trung gian ca min dch thu c.

5.1.1. Hnh thi hc Cc t bo lymph nguyn vn, tc l cc lymph bo cha tng tip xc vi khng nguyn trc c cc nh hnh thi hc gi l t bo lymph nh. T bo ny c ng knh 8-10mm, c nhn ln, vi cht nhim sc m c v mt vnh bo tng mng cha mt t ti th, ribosom v lysosom, nhng khng c cc tiu c quan chuyn mn ho (Hnh 5.2). Trc khi c kch thch khng nguyn, t bo lymph nh trng thi ngh, hay cn gi l trng thi G0 ca chu k t bo. Khi c kch thch, lymph bo nh chuyn sang giai on G1. Chng tr nn ln hn (ng knh 1012mm), c nhiu bo tng hn, c tiu c quan v gia tng lng RNA bo tng; lc ny n c gi l t bo lymph ln, hay nguyn bo lymph (Hnh 5.2).

Hnh 5.2. Hnh thi hc lymph bo Hnh nh knh hin vi quang hc ca lymph bo trn tiu bn mu ngoi vi 2. Hnh nh knh hin vi in t ca t bo lymph nh 3. Hnh nh knh hin vi in t ca t bo lymph ln (nguyn bo lymph)1.

5.1.2. Cc loi t bo lymph T bo lymph bao gm nhiu tiu qun th khc nhau khc bit v chc nng, v sn phm protein nhng khng phn bit c v hnh thi (Bng 5.2). Tnh a dng ca t bo lymph c gii thiu Chng 1. T bo B l t bo sn xut khng th. Chng c tn nh vy l v loi chim chng c trng thnh trong mt c quan gi l Bursa Fabricius (ti

Fabricius). loi c v, khng c c quan tng ng vi bursa v giai on u ca s trng thnh t bo B xy ra trong tu xng (bone marrow). Nh vy gi tn t bo B l ch rng t bo ny xut pht t bursa hoc bone marrow. T bo T l t bo trung gian ca min dch t bo, n c t tn nh vy l v cc t bo tin thn ca chng sau khi c