Modulation of polyclonal B cell differentiation by human leucocyte alpha interferon

Although interferon (IFN) profoundly affects immune responses in animals, less is known about its immunoregulatory activity in man. Therefore, peripheral blood mononuclear cells (PBM) from 20 healthy volunteers were incubated with pokeweed mitogen (PWM) in the presence and absence of human leucocyte alpha interferon (IFN alpha). In 18/20 experiments, IFN alpha added at initiation of culture markedly suppressed PWM-induced generation of immunoglobulin secreting cells (IgSC). IFN alpha suppressed proliferative responses in all experiments but the degree of suppression was not correlated with concomitant suppression of IgSC responses. Suppressive activity was resistant to pH 2 treatment but sensitive to treatment with trypsin. Delayed addition of IFN alpha was associated with decreased suppression. Suppression was not due to non-specific cytotoxicity since we observed (1) comparable viabilities in cultures with or without IFN alpha and (2) negligible effect when IFN alpha was added for the final 24 hr of culture. The data confirm previously described effects of IFN on mitogen stimulated PBM and, more importantly, provide convincing evidence that IFN alpha regulates human B cell functions.