B cell growth factor activity of interferon-gamma. Recombinant human interferon-gamma promotes proliferation of anti-mu-activated human B lymphocytes.

Abstract

Human B lymphocyte activation from small, resting B cells to larger activated B cells can be induced by cross-linking of surface IgM with anti-μ antibody or Staphylococcus aureus Cowan I bacteria. After activation, human B cells can undergo proliferation and differentiation into plasma cells in response to soluble factors released by T lymphocytes. Factors that promote B cell proliferation are generally referred to as B cell grown factors (BCGF), and for some years they had been considered to be distinct from interleukin 2 (IL2). More recently, however, both immunoaffinity-purified and recombinant IL 2 (rIL 2) were shown to act as a potent BCGF. Moreover, activated B cells have been shown to express receptors for IL 2 indistinguishable from those of activated T cells. Although BCGF activity may be largely related to IL 2, several experimental evidences indicate that molecules distinct from IL 2 may act as BCGF. In this report, we show that recombinant interferon-γ (rIFN-γ) promotes proliferation of anti-μ-activated human B lymphocytes. Moreover, a synergistic effect was observed when IL 2 was simultaneously added to cultures. Because the B cell proliferation induced by crude polyclonal supernatants was strongly reduced by the simultaneous addition of monoclonal antibodies to IL 2 receptors or to IFN-γ, it is likely that IL 2 and IFN-γ at least partially account for the T cell-derived BCGF activity.