B cells and humoral immune response 1. Recognition of the specific Ag 2. Activation proliferation, differentiation 2. Germinal center: laterevent 3. General feature of Ab response
B cells and humoral immune response 1. Recognition of the specific Ag 2. Activation, proliferation, differentiation 2. Germinal center: later event 3. General feature of Ab response
thymus-dependent (TD)antigens B response to TD Ag requires direct contact with Th cells thymus-independent (TI)antigens TI-1 Ag bacterial cell-wall components ipopolysaccharide (lps) TI-2 Ag highly repetitious molecules bacterial flagellin bacterial cell-wall polysaccharides with repeating units
highly repetitious molecules, bacterial flagellin bacterial cell-wall polysaccharides with repeating units. thymus-dependent (TD) antigens B response to TD Ag requires direct contact with Th cells, thymus-independent (TI) antigens TI- 1 Ag TI-2 Ag bacterial cell-wall components, lipopolysaccharide (LPS)
Recognition of TD Ag Thymus-dependent antigen ◇ Directly recognize Ag (B cell epitope) No MHC involvement B cell antigen surfaced displayed B cell-epitopes epitope antibody bcr
Recognition of TD Ag Directly recognize Ag (B cell epitope) No MHC involvement surfaced displayed B cell-epitopes
Antibodies bind to epitopes displayed on the o surface Ab(BCR)binds the B-cell epitope directly, of antigens TCR binds with a self-MHC-T-cell-epitope complex The epitopes recognized The antigen must first The epitope peptide binds The T-cell receptor binds to by T-cell receptors are be broken down into to a self molecule, an a complex of MHC molecule often buried peptide fragments MHC molecule and epitope peptide TCR epitope peptide molecule MHC molecule
Ab (BCR) binds the B-cell epitope directly, TCR binds with a self-MHC-T-cell-epitope complex
BCR-Iga/gB -coreceptor complex B cell epitope (cD21cD19-cD81) coreceptor C3d B cell epitope BCR Ag-C3d CR2 BCR CR2 Iga Igβ CD19 ga/b CD81 CD19 Signal ITAM ignal 3P13K B cell activation ++十
B cell activation B cell epitope BCR-Iga/Igb -coreceptor complex B cell epitope BCR Iga/b Signal + Ag-C3d CR2 CD19 Signal + +++ （CD21-CD19-CD81） coreceptor