3. RECALL Pathogens extracellular Antibodies secreted in 2 ND LT & Bone Marrow B cell function extracellular spaces Other Pathogens fluids B cell PM cell virus ~~~~~~ ~~~ Next cell bacteria Y Y Y intracellular virus
14. Protein or carbohydrate epitopes Bacterial cell Naïve Mature B cell IgM’s X-linked by repetitive Ag epitopes Ig Ig IgM Ig Ig Note that BCR signal transduction resembles that of TCR Signal transduction extracellular intracellular
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31. 9-4: Activation of naïve B cells by most antigens requires help from CD4 T cells
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37. Two signals B cell proliferation & differentiation into plasma cell B-cell activation in response to TD-Ag requires T cell help
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43. 9-7 Activated B cells undergo somatic hypermutation and isotype switching in the specialized microenvironment of the B-cell zone
44. Common theme of lymphocyte development B cell maturation in germinal center Activation proliferation selection Activation proliferation selection
45. Proliferation in the GC, Okay What about hypermutation and affinity maturation in the GC? centroblasts dividing in germinal center somatic hypermutation & isotype switching T-cell cytokines Nondividing centrocytes Mutated surface Ig Post hypermutation Surface Ig of centrocyte Affinity for a specific antigen higher lower equal
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47. Mutated centrocytes compete! To engage a helper T cell Centrocyte bind Ag process antigen surface = MHCII + Ag Mutated centrocytes now compete! Access of Ag on FDC’s Ag-specific helper T cells MHCII 1 2 Follicular dendritic cells provide a source of intact Ag Mutated centrocyte
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55. Chapter 9 – Lecture Notes Immunity Mediated by B Cells and Antibodies