Induction of proliferation and differentiation of neoplastic B cells by anti-immunoglobulin and T-cell factors.

Sepharose-bound anti-immunoglobulins, which are potent mitogens for normal adult B cells, are not mitogenic for tumor cells freshly isolated from mice carrying the B-cell leukemia BCL1. However, after 4 or more days of in vitro cultivation, BCL1 cells can be stimulated to divide by either anti-mu or anti-delta antibodies. These results suggest that in vitro cultivation of BCL1 cells results in their differentiation into more mature cells which can be triggered to proliferate by their interaction with anti-Ig antibodies. Addition of T-cell helper factors to anti-Ia treated BCL1 cells results in their differentiation into Ig-secreting cells. These results indicate that surface Ig molecules on BCL1 cells are capable of delivering an activation signal to the cells but that the cells require a second signal from T cells for induction of Ig secretion.