Blood groups and Hemostasis

Dpt. Of Normal, Pathological and Clinical Physiology

Blood groups

blood transfusion often resulted in agglutination and hemolysis, often led to death (renal shock)

antibodies in the plasma of one blood react with antigens on the surface of the red cells of another blood

more than 30 commonly occurring antigens

hundreds of rare antigens

two particular groups of antigens: AB0 and Rh systems are immunogenic enough to cause hemagglutination

AB0 system - history

Landsteiner Jánský actual nomenclature

A II A

B III B

C I 0

--- IV AB

AB0 system

four groups: A, B, AB, 0two (3) agglutinogens = antigens on the surface of RBCtwo agglutinins = antibodies present in the plasmaagglutinogens = glycoprotein, oligosaccharides having different carbohydrate at their endingsA – N-acetylgalactosaminB – galactoseH – fucosotransferasa

AB0 agglutinogens

determined by two genes, one on each of two paired chromosomes0 is functionless gene; O = “ohne”A gene determines A group; B gene determines B groupcodominancy:blood type A: genotype AA, A0blood type B: genotype BB, B0blood type AB: genotype ABblood type 0: genotype 00 (or hh “Bombay” + either AA, AO, BB, BO,

or AB)

+ Hh or HH

AB0 agglutinogens

antigen H forms the antigen-carrying moleculesubtypes of A antigen A1…A6, different immunogenitydetectable in 4weeks old embryoduring labor, 20-30% of the immunogenity in adult (> 18 years)

AB0 agglutininsantibodies present in the plasmaγ-globulins, IgG and IgM molecules (pentamers, not diffusing trough the placenta)

not present immediately after birthproduced in 2-8 months after birth by plasma cells (specialized B-cells, stimulated by similar oligosaccharides often expressed in the nature – food, intestinal bacterias)highest titer around at 10 years of ageantibodies against the AB0type not present in the bloodgroup A antibodies anti-Bgroup B antibodies anti-Agroup AB no antibodiesgroup 0 antibodies anti-A and anti-B

Frequencies of the different blood types

differ according to geographic and time locationsgroup A: Atlantic population and Eskimos (60%)group B: east-south Asia, India (40%)group 0: America's Indians (100%)the Czech Rep.: A-42 %, 0-32 %, B-18 %, AB-8 %white people: A-47 %, 0-41 %, B-9 %, AB-3 %

universal donor, universal acceptor - antigensautotransfusion

Rh system II

Landsteiner 1940C, D, E antigens (D is most immunogenic)

85 % white people Rh+, 99 % Asians Rh+, African black 100 % Rh+clinical importance:

1. blood transfusion 2. pregnancy: mother Rh negative and fetus Rh positive, antibodies diffuse

trough the placenta (erythroblastosis fetalis, new-born hemolysis, kernicterus, jaundice)

in both cases the exposition to the antigen is needed first (sensitization), because anti-Rh antibodies are NOT normally produced – Rh antigen is not often present in the nature

Other systems

MNSs: very low immunogens, normally no natural antibodies in blood occur, Landsteiner 1927P system: Landsteiner, low immunogens ( 80% people); subtypesKell, Duffy, Kidd, Lutheran, Diego

Hemostasis

three mechanisms:

1. vascular spasm2. formation of a platelet plug3. blood coagulation

Vasoconstriction

neural: nervous reflexes induces by activation of pain fibers, local myogenic spasmhumoral: thromboxan A2 and serotonin and other substances produced by activated plateletsvasoconstriction itself stops the bleeding in vessels as large as a. radialis (under ideal circumstances / i.e. crushed, not cut)

lasts for minutes or even hours

Plateletsdo not have nuclei, oval discs 2-4 m, half-life 4-8 daysmegakaryocytes (1000-5000 platelets)150 – 300.000 per 1 microliterplatelets cytoplasm contains:

1. actin and myosin and thrombosthenin (platelet contraction)2. vesicles containing Ca2+ , serotonin, ADP3. enzymes that synthesize prostaglandins4. -granules: PDGF, coagulating factors, von Willebrandt factor

(adhesion)5. lysozomyplatelets membrane contains large amount of phospholipids

platelets function

1. adhesion, collagen: vonWillebrandt Factor released from endothel

2. activation: swelling, irregular forms, pseudopods, release of serotonin, vWF, tromboxan A2, ADP activation of other platletes

3. aggregation: stimulated by trombin, tromboxan A2, vWF, fibrinogen platelet plug (loose, then fibrin threads form an unyielding plug)

closing the minute ruptures (small vessels, many times per day, petechiae)

Thrombopoetin

produced by the liver, little in kidney

receptors in plasma membrane of stem cells and megakaryocytes and platelets (regulation)

constant production, regulation by the number of platelets / the more platelets the more T bound to them less T act on stem cells and megakaryocytes liver diseases bleeding (together with lower production of clotting factors)

clotting pathways

the sense is to form fibrin monomers and then polymers = fibrin fibers (threads) within few seconds (and pesence of Ca2+) fibrin is formed by activated thrombin all activators of prothrombin are called trombokinases (tissue and plasmatic trk)

intrinsic pathway extrinsic pathway

common

clotting factors - proenzymes

I fibrinogen VIII AHF A

II prothrombin* IX Christmas (AHF B)*

III tissue thromboplastin X Stuart-Prower*

IV calcium XI AHF C

V proaccelerin XII Hageman

VII proconvertin* XIII fibrin-stabilizing

* vitamin K dependent

clotting pathway – common

X Xa: activated either by intrisic or extrinsic pathway

II IIa: protrombin, trombin

XIII XIIIa I Ia: fibrinogenfibrin

+V

stabilization

I fibrinogen

II prothrombin*

III tissue thromboplastin

IV calcium

V proaccelerin

VII proconvertin*

VIII AHF A

IX Christmas (AHF B)*

X Stuart-Prower*

XI AHF C

XII Hageman

XIII fibrin-stabilizing

I fibrinogen

II prothrombin*

III tissue thromboplastin

IV calcium

V proaccelerin

VII proconvertin*

VIII AH A

IX Christmas (AH B)*

X Stuart-Prower*

XI AH C

XII Hageman

XIII fibrin-stabilizing

XII XIIa: catalyzed by kalikrein a kininogen, activated by negative charges (glass, collagen)

XI XIa: activated by XIIa

IX IXa: activated by XIa

X Xa1 – 6 minutes

+VIII

clotting pathway – intrinsicsubmucosis, phospholipids released from platelets

I fibrinogen

II prothrombin*

III tissue thromboplastin

IV calcium

V proaccelerin

VII proconvertin*

VIII AHF A

IX Christmas (AHF B)*

X Stuart-Prower*

XI AHF C

XII Hageman

XIII fibrin-stabilizing

clotting pathway – extrinsictissue, lipoproteins

VII VIIa: activated by tissue factor III (thromboplastin) which is released from damaged tissues

X Xa: activated by VIIa

10 seconds, explosive

(VIIa activates IX of intrinsic pathway as well)

anticlotting mechanisms

endothelial smoothness, glycocalyx (mucopolysaccharide repelling the factors) and thrombomodulin (protein binding thrombin)

fibrin itself remove thrombin from the bloodcatching of activated factors by liverconsumption of activated factorsantithrombin III: proteases inhibitor, its binding is facilitated by heparin

no activation of IX, X, XI, XIIheparin – polysaccharide released from mast cells and basophils

fibrinolysis

thrombomodulin (endotelial wall) catalyzes activation of protein C by thrombinactivated protein C (APC)

1. inactivates VIII2. inactivates V3. activates tissue plasminogen activator (TPA)

TPA catalyzes activation of plasminogen to form plasmin, plasmin causes lysis of the clotalteplase (recombinant), streptokinase, urokinase

anticoagulants

heparin (+ antithrombin III)citrate, oxalate (bind Ca2+)coumarin, warfarin (inhibition of vitamin K)

excessive bleeding

failure of blood clotting (coagulopathy)– hematoms, joint bleeding

platelets failure thrombocytopathy– petechiae

vessels defects– petechiae

innate coagulopathy

abnormality or deficiency of one of the clotting factorshemophilia A, classic h.– defect of VIII (3 subunits, defect of the clotting factor)– transmitted genetically, X chromosome, males– hemophilic arthropathy, muscle bleeding in legs– 1 z 10000 born males

von Willebrandt disease: defect of VIII, all subunits impaired (vW factor, antigen factor and clotting factor)

hemophilia B: defect of IXother disorders when impaired factors I, II, V, VII, X, XIIIdeficiency of XI almost without any clinical signs

acquired coagulopthies

liver diseases (cirrhosis) – deficiency of all factorsheparindeficiency of vitamin KDIC– sepsis, leukemia, AB0 incompatibility

defects of platelets

trombocytopenia: aplasia (radiation), hypovitaminosis B12, sequestration

trombocytopathy: acetylsalicylic acid (inhibition of COX suppresses synthesis of thromboxan A2 and secretion of ADP

Defekty cév

von Willebrandtova choroba: defekt endotelu, chybí vWF porucha adheze, nedostatek VIII (vWF je jeho přenašeč)skorbutvrozené defekty pojiva: Rendu-Osler, Henoch-Schönlein