Monoclonal anti-Fc IgG receptor antibodies trigger B lymphocyte function

Despite intensive investigation, it remains unclear which receptor(s) on the B lymphocyte receives the signal(s) which leads to differentiation and antibody secretion. Binding of ligand (that is, specific antibodies) to the antigen receptors IgM or IgD, in the absence of T lymphocytes or their soluble products, leads to proliferation of normal B cells but not to antibody secretion 1,2 . Based on the observation that IgG Fc receptors (Fc γ R) have specific and unique interactions with other B-lymphocyte surface membrane molecules including I -region antigens 3 , IgM 4 and IgD 5 , it was suggested that Fc γ R assist in regulation of B-lymphocyte responses 5 . Here we demonstrate that monoclonal antibodies specific for Fc γ R trigger normal B cells both to proliferate and to secrete antibody in the absence of T lymphocytes. These data suggest that the functional activation of B lymphocytes during normal immune responses may be mediated by Fc γ R.