Anti-CD3 antibodies induce T helper function for human B cell differentiation in vitro by an interleukin 2-independent pathway.

Previously we have shown that interleukin 2 (IL 2) is an essential mediator in T cell-dependent B cell differentiation induced by pokeweed mitogen. Here we show that activation with monoclonal anti-CD3 antibodies of peripheral blood T cells led to the induction of helper activity for IgM secretion by human B cells from a prolymphatic leukemia. With the use of monoclonal antibodies against the IL 2 receptor and CD3+CD4+CD8- chronic lymphatic leukemia T cells with a strongly reduced capacity to produce IL 2, it was demonstrated that the anti-CD3-driven Ig secretion was obtained by an IL 2-independent pathway. The T cell help in this system is mediated by soluble factors.