Insulin-Like Stimulatory Effect of Fc Fragments of Human Immunoglobulin G on Rat Adipocyte Lipogenesis: Indirect Evidence for Fc Receptor on Adipocytes

We have recently shown that human immunoglobulin G (IgG) exerts an insulin-like stimulatory effect on lipogenesis by rat and human adipocytes in vitro. Highly purified polyclonal IgGs prepared from normal subjects have stimulatory potencies similar to those of monoclonal IgGs obtained from patients with IgG myeloma. These observations suggest that this effect is probably exerted by a nonspecific nonvariable portion of the IgG molecule. We now present data to show that the Fc moiety of the IgG molecule is responsible for the stimulatory effect of this IgG molecule. These data also provide evidence for the first time that adipocytes may have Fc receptors.