Chapter 10 Immune system

1. Components 1)      Cells

① Lymphocyte: a. T-lymphocytes: cytotoxic T cell: Tc C- kill the tumor cell, virus infective cell and foreign cell helper T cell: Th C- promotes activity of BLC and Tc C suppressor T cell: Ts C –regulate the function of BLC and TC b. B-lymphocytes: become into plasma cell c. NK cell: counteract virus infective cell and tumor cell

②Plasma cell ③antigen presenting cell: a. dendritic cell: Blood DC Langerhans cell interstitial cell veiled cell interdigitating cell b.macrophage: mononuclear phagocytic system

④other cells: granulated cell mast cell blood platelet blood-borne stem cell *Function: i.      immunologic defence function ii.     immune surveillance function iii.    immune homeostasis

2)     Lymphoid tissue ---reticular T: reticular cell: stellate-shaped with processes to form network reticular fiber ---lymphocytes, macrophage, plasma cell and mast cell

a. Diffuse LT: no clear boundary mainly consists of TLC postcapillary venules: -high endothelial venules -opening for LC enter LT from blood

b. Lymphoid nodule: spherical or ovoid have clear boundaries mainly composed of BLC germinal center: stained pale * primary LN → secondary LN

3) Lymphoid organs a. Central lymphoid organs: thymus, bone marrow developed earlier blood-borne stem cell comes from yolk sac microenvironment → proliferation promoting send LC to PLD and LT two weeks before borne

b. Peripheral lymphoid organs: lymph node, spleen and palatine tonsil developed later LC come from CLO cell proliferation need antigen stimulating- antigen dependent place for immune reactions

2.thymus Structure of thymus ---capsule: CT→interlobular septum ---cortex: dark-staining ---medulla: lighter-staining ---consists of thymic epithelial cell, thymic stromal cell( ma, eo,mc, fibroblast and myoid cell) and thymocytes

①cortex: ---thymic epithelial cell(epithelial reticular cell): subcapsular epithelial cell: /flattened /secret β 2-microglobulin, thymosin and thymopoietin interdigitation dendritic cell: /more processes /MHC antigen ---thymocyte: different stages of LC large LC( prethymocyte): superfacial cortex common thymocyte: deep cortex- 85-90%

2) medulla: ---epithelial reticular cell medullary epithelial cell: secret thymosin thymic corpuscle epithelial cell * thymic corpuscle: /spherical or ovoid, 30-50um in D /concentrically-arranged epithelial reticular cells /peripheral cell: inmature /near centra: mature /center cell: keratinased-eosinophilic, hyalinised, with invading of macrophage, eosinophil and LC /function: unknown ---thymocyte, macrophage

3) Blood-thymus barrier: ---Components Contineous endothelial cell Complete basement membrane of endothelium peri-vessel space containing macrophage basal lamina of epithelial reticular cell Processes of epithelial reticular cell ---Function: provide a stable environment for lymphocytes development

4) function: a. Place for mature and differentiation of TLC b. Immune regulation

3. Lymph node ---widely distributed ---in groups ---ovoid or kidney-shaped with hilum ---afferent and efferent lymphatic vessel

1) Structure ---capsule: CT, trabeculae or septa ---cortex: outer densely-stained part ---medulla: inner paler-stained part

①Cortex: a. superfacial cortex: ---lymphoid N: BLC, Macrophage, FDC, Th primary LN → secondary LN *germinal center: central pale area /dark zone: large, immature BLC, Th /light zone: medium-sized BLC, Th C, macrophage, FDC /cap: small BLC: mature←supermutation ---diffuse LT: thin layer

FDC: (follicular dendritic cell) light zone no expression of MHC-II molecules (major histocompatibility complexes) have Fc receptor and C3 receptor: collect the antigen-antibody complexes and transfer them to BLC and Th C function: i. active the BLC ii. regulate the synthesis of antibody

b.Paracortex zone-deep cortex unit ---diffuse LT: TLC, Marcophage, Th cell interdigitating cell: DC cell -more processes -N: irregular -less organelle -express MHC-II postcapillary venules: -thick endothelial cell -LC within the wall -opening for LC enter LN

c. Cortical sinus ---subcapsular sinus: afferent LV enter ---peritrabecular sinus ---structure: endothelium RF and RC cavity: -endothelial cell: stellate for support -macrophage: filter lymph -veiled cell: Langerhans cell ( phagocytose antigen) → efferent LV → LN → paracortex zone

②Medulla ---medullary cord: LT cord: /BLC, plasma cell, macrophage, mast cell /postcapillary venules: channel ---medullary sinus: /similar to cortical sinus and connect with C S /more macrophage

③Passage of Lymph in LN afferent LV →subcapsular sinuses→peritrabecular sinuses→(narrow channel) →medullary sinus→efferent LV

3)      Functions: a.Filter the lymph b.Place to give rise to the immune response c. Involve in the recirculation of LC *Recirculation of LC: LC(blood) →(postcapillary venules) → LN → medulla → efferent LV → Blood →LN artery → postcapillary venules →LN Time: 24-48h

4. Spleen 1) Structure ---capsule: thick DCT with SM and mesothelium, also form trabeculae ---white pulp ---marginal zone ---red pulp

① White pulp: 1-2mm gray-white spots periarterial lymphatic sheath: -central artery -diffuse LT : TLC, macrophage, interdigitating cell splenic corpuscle: -BLC, macrophage, FDC -lymphoid nodules

② Marginal zone: 100um width TLC, BLC, macrophage, less erythrocyte marginal sinus: central artery’s branch- channel for antigen and LC enter LT place: capture recognize and induce immune reaction

③ Red pulp: constitute about 2/3 of splenic volume a. splenic cord: LT cord BLC, DC. M, TC , erythrocytes place: filter blood b. splenic sinus: Blood sinus; 12-14um endothelial cell: rod-liked, gap RT basal lamina: incomplete M-more

2) Blood supply of spleen splenic A→trabecular A→central A branches → marginal sinuses penicillar Arterioles(including: pulp arteriole→ sheathed capillary→ arterial capillary) → splenic sinus→ pulp venule→ trabecular vein→ splenic vein

3) Function: a. filter the blood b. immune reaction c. production of blood in fetus d. blood storage: 40 ml

5. tonsil ---palatine tonsil ---pharyngeal tonsil ---lingual tonsil

palatine: ---structure: Stratified squamous epi: invaginated to form many crypts Epithelium of crypt contain LC, PC, Ma and Langerhans cell Space and channel between epi.cell: opening to crypt epi. surface, LC filling the channel- lymphoepithelial tissue Lamina propria: Diffuse LT and LN