A Transforming Growth Factor (3-like Immunosuppressive Factor in Immunoglobulin Gbinding Factor

Immunoglobulin G-binding factors (IgG-BF), which are produced by cells of the immune system, inhibit antibody production . In this paper, we show that transforming growth factor-(3 (TGF-(3) suppresses secondary in vitro anti-sheep red blood cell responses of mouse splenocytes and lipopolysaccharideor anti-IgM--stimulated mouse B cell responses in a way similar to, and with the same kinetics as, rodent IgG-BF . Moreover, the immunosuppressive activity ofIgG-BF was totally neutralized by polyclonal and monoclonal anti-TGF-(3 antibodies and it eluted with TGF-(3 by gel exclusion chromatography, suggesting that a TGF-R-like immunosuppressive factor is present in IgG-BF . We also show that TGF-R behaves as an IgG-BF since it binds to insolubilized IgG, but not to insolubilized F(ab') 2 or bovine serum albumin . Altogether, the data support the concept of a biological role for TGF-(3 in the IgG-mediated negative feedback of antibody responses .