Figure 9.5

   Armed helper T cells stimulate the proliferation and then the differentiation of antigen-binding B cells

The specific interaction of an antigen-binding B cell with an armed helper T cell leads to the expression of the B-cell stimulatory molecule CD40 ligand (CD40L) on the helper T-cell surface and to the secretion of the B-cell stimulatory cytokines IL-4, IL-5, and IL-6, which drive the proliferation and differentiation of the B cell into antibody-secreting plasma cells.