Interferon-alpha suppresses the capacity of T cells to help antibody production by human B cells.

This study was designed to analyze the effect of interferon-alpha (IFN-alpha) on the potential of T cells to help B-cell differentiation in vitro. Human splenic T cells preactivated via the T-cell receptor (TCR)/CD3 complex, as well as murine EL4 thymoma T cells preactivated with phorbol esters, stimulated human B cells via a species cross-reactive physical interaction to differentiate into antibody-producing cells. If the human or murine T cells were activated in the presence of IFN-alpha, normal proliferation and interleukin-2 (IL-2) production occurred, but the cells did not acquire any B-cell helper potential. Therefore, IFN-alpha modulates the B-cell stimulatory potential of T cells by interfering with the T-cell activation process. In contrast, IFN-alpha neither acted on B cells directly nor on already activated T cells, because it did not suppress B-cell differentiation induced by T cells preactivated in the absence of IFN-alpha. IFN-alpha did not induce the production of inhibitory T-cell factor(s), since T cells preactivated in the presence of IFN-alpha did not inhibit the interaction of B cells with T cells optimally preactivated in the absence of IFN-alpha. Taken together the data indicate that IFN-alpha suppresses the potential of T cells to stimulate B-cell differentiation by interfering with the T-cell activation process, but acts neither on B cells directly nor on already activated T cells.