The functions of antigen recognition in T cell-dependent B cell activation.

B cells get help from T cells by acting as antigen-specific APC. A signal from the B cell antigen receptor is not required for efficient antigen presentation or for the B cell response to T cell help. T cells provide help by making lymphokines, some of which, like CD40 ligand, remain T cell-associated and require cell contact for function. The function of class II MHC is to induce help in the T cell, rather than to deliver help to the B cell. T cell help uses different intracellular signaling pathways from those engaged by the B cell antigen receptor.