Recombinant interleukin 2 induces proliferation and differentiation of human B lymphocytes

Highly purified normal human tonsillar B lymphocytes were cultured with recombinant IL 2 (rIL 2). The responses were minimal when the cells were cultured with rIL 2 alone. Dose-dependent proliferation and differentiation into immunoglobulin-secreting cells were found when the cells were simultaneously activated with Staphylococcus aureus Cowan I (SAC). T cells were not found to proliferate in these cultures. B-cell responses were not augmented when 16% T cells were added to the B-cell population. In contrast, B-cell proliferation and Ig secretion were significantly enhanced by adding 0.5% T cells when cultured in the presence of pokeweed mitogen (PWM). Moreover, B-cell stimulation by rIL 2 was detected at very low cell densities. It is concluded that IL 2 directly affects the function of activated B cells.