Influence of interferon γ on B cell replication

Abstract

Semisolid agar culture techniques, recombinant murine gamma interferon, (Mu IFN γ) and monoclonal anti- Mu IFN γ antibodies were used to evaluate the role of interferon in mitogen-dependent B cell proliferation. Subtle, but significant, effects of interferon addition were noted when unseparated spleen cells were cultured. Depending on culture conditions, the cloning efficiency of the B cells was slightly increased by optimal concentrations of interferon. When the spleen cells were cultured over unstimulated peritoneal macrophages separated by an agar spacer, and especially when no other potentiators were added to the cultures, substantial enhancement of B cell proliferation routinely resulted. The mechanism of this effect was then investigated with macrophage depleted spleen cells as well as highly enriched, positively selected, B cell suspensions. Results of these experiments indicated that B cell replication can be modulated by direct interaction with interferon and again, the conditions of culture determined the magnitude and direction of the effect. Addition of anti-interferon antibodies, indomethacin, or interleukin 1 (IL-1) to the cultures did not influence the cloning efficiency of normal splenic B cells. Therefore, we found no evidence that endogenously produced interferon, prostaglandins, and IL-1 influence B cell colony formation. Since interferon stimulated macrophages dramatically improved B cell proliferation without direct cell contact, some other monokine may be involved. Therefore, gamma interferon can participate in humoral immune responses by influencing the expansion of activated B cells directly as well as indirectly via stimulation of macrophages.