lymphoid organs and system. lymphoid tissues (primary lymphoid organs) thymus, b.m., (in embryonic...

Download Lymphoid organs and system. lymphoid tissues (Primary lymphoid organs) Thymus, B.M., (in embryonic course comprise Yolk sac, Liver and spleen) lymphoid

Post on 18-Jan-2016

230 views

Category:

Documents

0 download

Embed Size (px)

TRANSCRIPT

  • Lymphoid organs and system

  • lymphoid tissues (Primary lymphoid organs) Thymus, B.M., (in embryonic course comprise Yolk sac, Liver and spleen)

    lymphoid tissues (Secondary lymphoid organs) Lymph nodes, Liver Spleen, Lymphocytes, NK, MONO, MQ, DCs, NEUT, EOS,..

    Immune response sites (Tertiary lymphoid organs) Any where that immune system fight with organismsLymphoid Organs

  • Th, CD3+, CD4+Tc, CD3+, CD8+B , CD19+, CD20+NK, CD16+, CD56+MQ, CD14+DC, CD11c+Production of nave (in mice 1-3 months) lymphocyte is under equilibration with lymphocyte death with apoptosis (homeostasis)Self- renewing

  • T Cells80% of circulating lymphocytesSome of the types:Cytotoxic T cells: attack foreign cells or body cells infected by viruses (cell-mediated immunity)Regulatory T cells: Helper T cells and suppressor T cells (control activation and activity of B cells)Memory T cells: produced by the division of activated T cells following exposure to a particular antigen (remain on reserve, to be reactivated following later exposure to the same antigen)Memory T cells (CD44 high) CD45RO whereas Naive T cell express CD45RA receptor.

  • B Cells10-15% of circulating lymphocytesCan differentiate into plasmocytes (plasma cells) when stimulated by exposure to an antigenPlasma cells produce antibodies: soluble proteins which react with antigens, also known as immunoglobulins (Igs)Humoral immunity, or antibody-mediated immunityMemory B cells: produced by the division of activated B cells following exposure to a particular antigen (remain on reserve, to be reactivated following later exposure to the same antigen)

  • NK Cells5-10% of circulating lymphocytesAttack foreign cells, normal cels infected with viruses, cancer cells that appear in normal tissuesKnown as immunologic surveillance

  • What are T cells?Migrate from marrow and develop in thymusHave antigen receptors on PM = immunocompetentMitosis produces clonesClonal deletion destroys self-reactive clonesGood at destroying cells and stimulating B cellsThey do NOT secrete antibodies as B cells doT cell types movie

  • DCDC

  • T cells (helper and cytotoxic) feel cellsCheck for MHC (hotdog bun)MHC = major histocompatibility complexMHC-I on all cellsMHC-II only on APCsHLA (human leukocyte antigen) group = MHC

  • Dendritic cells known as professional APC

  • Lymph nodes Spleen Thymus Peyers patches Tonsils Red Bone Marrow Appendix

    Lymph Organs:

  • Part of the immune system that consists of 2 independent parts:meandering network of lymphatic vesselsvarious lymphoid tissues and organs

    Lymphatic system is located within loose connective tissue systems of the bodyThe Lymphatic System

  • Lymphatic SystemConsists of three partsA network of lymphatic vessels (lymphatics)Lymph - a fluidLymph nodes

  • Lymphatic CapillariesAbsent from teeth, bone marrow and the CNS (Brain lacks immune system generally)Lacteals: specialized lymph capillaries present in intestinal mucosaAbsorb digested fat and deliver fatty lymph (chyle) to the blood

  • Lymphatic SystemOne way system: to the heartReturn of collected excess tissue fluidReturn of leaked proteinLymph is this fluidEdema results if system blocked or surgically removed

  • Lymph capillariesHave one way minivalves allowing excess fluid to enter but not leavePicks up bacteria and viruses as well as proteins, electrolytes and fluid(lymph nodes destroy most pathogens)

  • Dynamics of Capillary Exchange

  • Figure 20.2aCervical nodesEntrance of rightlymphatic duct into veinInternal jugular veinEntrance of thoracicduct into veinThoracic ductCisterna chyliLymphaticcollecting vesselsAxillary nodesAortaInguinal nodesRegionallymph nodes:(a) General distribution of lymphatic collecting vessels and regional lymph nodes.Drained by the rightlymphatic ductDrained by thethoracic duct

  • Fig. 22.04Systemic Circulation

  • HEV; High endothelia venule that present in Lymph node and Pier patches but not in spleen.

  • Formation of Lymph

  • What does the lymphatic system do?Return interstitial fluidCapillaries only reabsorb 15%Funneled into subclavian veins Absorb and transport lipids from intestinesGenerate and monitor immune responseslymphatic system movie

  • Lymphatic System: FunctionsReturns interstitial fluid and leaked plasma proteins back to the bloodOnce interstitial fluid enters lymphatics, it is called lymphTogether with lymphoid organs and tissues, provide the structural basis of the immune systemAntigen concentration and focusing

  • Lymphatic CapillariesSimilar to blood capillaries, exceptVery permeable (take up cell debris, pathogens, and cancer cells)Endothelial cells overlap to form one-way minivalves, and are anchored by collagen filaments, preventing collapse of capillaries

  • Form a 1-way system in which lymph fluid flows only toward the heart Vessels are similar to capillaries, but very permeable. They occur everywhere blood capillaries occur.Lymphatic vessels

  • Lymph Transport lacks pump for circulation relies on activity of skeletal muscles and pulsation of nearby arteries for movement of fluid 3L of lymph enters blood stream every 24 hrs proteins easily enter lymphatic system uptake of large particles such as cell debris, pathogens, and cancer cellslymph nodes where it is cleansed of debris and examined by cells of the immune system.

  • Lymph node anatomy(FDC)Cytokine determined anatomical distribution of immune cells in L.N. and CCR7 helps DC and Lym and CXCR5 for Ln-B to transfer to lymph nods. Cell migration through HEV carried out in Cortex area. LT-B is important in lymph node formation.

  • What is in the lymphatic system?Lymph nodesFilters lymph fluid for antigens, bacteria, etc.B-lymphocytes made hereSome T-lymphocytes and macrophages congregate Afferent (more) and efferent (less) vessels lymph fluid exits through hilumCommon site for cancerWhy?Hodgkins lymphoma: lymph node malignancyEtiology unknownNon-Hodgkins lymphoma: all other cancers of lymphoid tissueMultiplication/metastasis of lymphocytes5th most common cancer

  • The Lymphatic system

  • Afferent lymphaticvesselsEfferent lymphaticvesselsCapsuleTrabeculaeHilumCortex Lymphoid follicle (B cell rich zone) Germinal center Subcapsular sinusMedulla: Medullary cord Medullary sinus(a) Longitudinal view of the internal structure of a lymph node and associated lymphatics

  • lymphatic capillariesblood capillarieslymphatic vesselslymphatic nodeone-way valves

  • Figure 20.2aCervical nodesEntrance of rightlymphatic duct into veinInternal jugular veinEntrance of thoracicduct into veinThoracic ductCisterna chyliLymphaticcollecting vesselsAxillary nodesAortaInguinal nodesRegionallymph nodes:(a) General distribution of lymphatic collecting vessels and regional lymph nodes.Drained by the rightlymphatic ductDrained by thethoracic duct

  • Fig. 22.03

  • After Antigen stimulation Flow rate to Lymph node increase more than 20 times.

  • SpleenLargest lymphoid organServed by splenic artery and vein, which enter and exit at the hilusFunctionsSite of lymphocyte proliferation and immune surveillance and responseCleanses the blood of aged cells and platelets, foreign matter, bacteria, viruses and debrisStores breakdown products of RBCe.g. ironErythrocyte production in fetus (normally ceases after birth)

  • Structure of the SpleenTwo distinct areasWhite pulp around central arteriesMostly lymphocytes on reticular fibers and involved in immune functionsRed pulp in venous sinuses and splenic cordsRich in macrophages for disposal of worn-out RBCs and bloodborne pathogens

  • (b) Diagram of spleen histologySplenicarterySplenicveinHilum(a) Diagram of the spleen, anterior viewWhite pulp; Adjacent to artery and contain PALS, Follicle and marginal zoneRed pulp; Adjucent to tiny venule and contain RBC, MQ, DC, Ln, and plasmacell.Red pulp area contains MQ that deleted opsonized bacteria such as Meningococcal, Pneumonococci

  • ThymusLocated: on top of heart Secretes hormones thymosin and thymopoeitin Causes T-lymphocytes to function against specific pathogens in the immune response (called immunocompetent) Most active during youth; it in size during childhood, by old age, it's mostly been replaced by fibrous and fatty connective tissue

  • ThymusDiffers from other lymphoid organs in important waysIt functions strictly in T lymphocyte maturationIt does not directly fight antigensThe stroma of the thymus consists of star-shaped epithelial cells (not reticular fibers)These thymocytes provide the environment in which T lymphocytes become immunocompetent

  • ThymusThymic lobes contain an outer cortex and inner medullaCortex contains densely packed lymphocytes and scattered macrophagesMedulla contains fewer lymphocytes and thymic (Hassalls) corpuscles involved in regulatory T cell development

  • Figure 20.7CortexMedullaThymic (Hassalls)corpuscle

  • Immune system in skinLangerhans cells after antigen capture immigrate to derma area. IEL contain TCD8+ cells.

  • MALTMucosa-associated lymphatic tissue, includingPeyers patches, tonsils, and the appendix (digestive tract)Lymphoid nodules in the walls of the bronchi (respiratory tract)Protects the digestive and respiratory systems from foreign matter

  • Mucosal Immune system (Three compartment)ABCIn mice 50% and in human 10% of such T cells are CD8+Most T cells in lamina properia are activated CD4+

  • Aggregates of Lymphoid FolliclesPeyers patchesClusters of lymphoid folliclesI

View more >