Interferon-alpha can synergize with interleukin 2 for human in vitro antibody response

We tested the effect of interferon (IFN)-alpha on the specific anti-2,4,6-trinitrophenyl (TNP) response induced by TNP-conjugated polyacrylamide beads in cultures of purified human B cells. IFN-alpha alone had no effect. Interleukin 2 (IL2) alone had a restorative effect which could be considerably (10X) enhanced by IFN-alpha. This reflected a true synergy most apparent with IL2 concentrations of 10 U/ml and IFN-alpha concentrations of 10(3)-10(5) U/ml. The highest concentrations of IFN-alpha were not inhibitory. In contrast, IFN-alpha did not enhance the effect of an IL2-free T cell-derived supernatant able to support the B cell differentiation. Sequential incubations showed that IFN-alpha acted earlier than IL2 on B cell response. The effect of IFN-alpha was dependent on an efficient interaction between IL2 and its receptor which could be inhibited by a monoclonal antibody toward the CD25 antigen. Thus, IFN-alpha can positively interact with a well defined interleukin, IL2, at a pre or post receptor level to potentiate antibody response.