GENERATION OF MEMORY B-CELLS AND PLASMA-CELLS IN-VITRO

After germinal center B cells undergo somatic mutation and antigen sel ection, they become either memory B cells or plasma cells, but the sig nal requirements that control entry into either pathway have been uncl ear. When purified human germinal center cells were cultured with inte rleukin-2, interleukin-10, and cells expressing CD40 ligand, cells wit h characteristics of memory B cells were generated. Removal of CD40 li gand from the system resulted in terminal differentiation of germinal center B cells into cells with the characteristics of plasma cells. Th ese results indicate that CD40 ligand directs the differentiation of g erminal center B cells toward memory B cells rather than toward plasma cells.