医学免疫学英文版课件：Chapter14Recognition and Immune Response of B cells to Antigens

1、Chapter16 Recognition and Immune Response of B cells to AntigensB cells mediated immune responseHumoral immunity(HI) or antibody mediated immunity: The total immunological reaction that B cells recognize antigen, then activate, proliferate, differentiate into plasma cells and produce Ab. B2 cells me

2、diated immune response to TD-AgB1 cells mediated immune response to TI-AgContents Part Immune response of B2 cell to TD-Ag Part Immune response of B1 to cell TI-AgPart Rules of humoral immunityPart Immune response of B2 cell to TD-AgCharacteristics of TD-Ag:Possess T cell epitope and B cell epitopeN

3、eed Th cells participationBoth CMI and HIProduce several types of antibodies: IgGProduce immune memory Part Immune response of B2 cell to TD-Ag B2 cells recognize TD-Ag activate, proliferate,differentiate plasma cells produce Ab1.B cells recognize antigenBCR directly recognize the conformational det

4、erminant on the surface of AgNo APC , no MHC restrictionCapture Ag by BCR, present Ag signal to Th cells2. B cells activation, proliferation and differentiation (1) B cell activation: double signals First signal : antigen signal BCR-conformational determinant on the surface of Ag Ig/Igtransduct firs

5、t signal CD19/CD21/CD81/CD225 (co-receptor) binds to C3d on AgSecond signal: co-stimulatory signal The CD40 on B cells binds to CD40L on activated T cellsCD225(Leu-13) Activation of Th : APC present peptide-MHC II complex and provide B7 to T cell, T cell activate and express CD40L Th provide co-stim

6、ulatory signal to B cells:TCR on activated Th recognizes antigen peptide-MHC II molecules complex presented on B cell， CD40L on T cell bind to CD40 on B cells to pass co-stimulatory signal to B cell Second signal: -the help of Th cells to B cellsSites of T cells helping B cellsT cell regionGerminal

7、centreSpecific helpBystander helpInteraction between Th cell and B cellB cells act on Th cells:B cells present Ag to Th cellsB cells provide B7 for Th cellsTh cells act on B cells:Activated Th cells provide co-stimulatory molecule for B cells: CD40LCD40Activated Th produce Cks（IL-4、IL-5、IL-6、IL-10、I

8、L-13）which help B cells proliferation and differentiation(2) B-cell proliferation and differentiation-help of Th Activated B cells express receptors of cytokines(IL-2R, IL-4R, IL-5R )Activated Th2 secrete cytokines IL-2, IL-4, IL-5 to enhance proliferation and differentiation of B cells B cells diff

9、erentiate into plasma cells ( antibody forming cells)- produce Ab, part into memory B cells免疫记忆免疫记忆 Differentiation of B cell in germinal CenterReceptor revisionV(D)J re-rearrangementSome B cells differentiate to the plasma cells which produce IgM During proliferation and differentiation, Somatic hy

10、permutation of B cells induces affinity maturation of AbSome B cells have an isotype switch to produce other types of Ig Production of memory B cells C C C3 C1 C1 C2 C4 C C2C3. Stage of effect-the function of AbNeutralizationActivate complement systemADCCNKOpsonization - macrophage Part Immune respo

11、nse of B1 to cell TI-Ag Characteristics of TI-Ag:Repeat B cell epitopeNo T cells participationOnly humoral immunityOnly produce IgMNo immune memory Part Immune response of B1 to cell TI-Ag B1 cells recognize TI-1 Ag: TI-1 Ag usually called B cell mitogen High TI-1 Ag can induce polyclonal B cells pr

12、oliferation and differentiationLow TI-1 Ag only stimulate B cell clone with specific BCRResponse of B1 cell to TI-1 Ag earlier than that of B2 cell to TD-AgNo Ig isotype swicth, affinity maturation, and memory B cells Part Immune response of B1 to cell TI-Ag B1 cells recognize TI-2 Ag :Most TI-2 Ags

13、 belong to cell wall of bacteria and capsule polysaccharide with high repeat strutureOnly stimulate mature B1 cellsDensity of epitope is key to TI-1 Ag activating B cellsHelp macrophage phagocyte and digest extracellular bacteria under antibody of capsule polysaccharidePart Rules of humoral immunity 1. Primary response 2. Secondary response lag activity type maintaining phase affinity time primary Ir longer low IgM shortersecondary Ir shorter high IgM, IgG longerSignificance: On diagnosis: IgM is a marker for early diagnosis of infectious diseaseOn vacc