抄録
Germinal center (GC) develops in secondary lymphoid tissues in response to thymus-dependent antigens (Ag), Ag-specific B cells are first activated in the T cell rich zones by T cells. Following conjugate formation between the T and B cell, Ag-specific B cell differentiation take place in two distinct sites, antibody forming cells (AFC) foci and GC. Recently has it been recognized that (i) B cell clonal expansion, (ii) somatic hypermutation in the variable (V) -region genes of immunoglobulin, (iii) selection on the basis of their ability to receive Ag-specific signals, (iv) isotypeswitching, and (v) the subsequent induction to differentiate into plasma cells or memory B cells take place in GCs. CD401igand-CD40 interaction is suggested to play crucial roles in these differentiation of GC B cells. We found that a significant proportion of mouse GC B cells expresses receptors (R) for IL-4 and IL-5. IL-4 in the presence of anti-CD40 mAb enhances viability of GC B cells, is essential for inducing differentiation of GC B cells into Ag-specific IgG1 AFC, and enhances the IL-5R expression on GC B cells. IL-5 further augments the IgG1 AFC response. We also discuss GC development and function of GC B cells in some mutant mice.
