IgG1 is the predominant subclass ofin vivo- andin vitro-produced anti-tetanus toxoid antibodies and also serves as the membrane IgG molecule for delivering inhibitory signals to anti-tetanus toxoid antibody-producing B cells

Abstract

Peripheral blood leukocytes from individuals immunized with tetanus toxoid can be stimulated by pokeweed mitogen to produce IgG anti-tetanus toxoid antibody (IgG-Tet)in vitro. Previous studies have shown that treatment of these cells with tetanus toxoid or anti-human IgG reagents can inhibit thisin vitro antibody synthesis. We have examined the four IgG subclasses on the surface of B cells for their relative contributions in the anti-IgG antibody-induced inhibition of IgG-Tet production. With all donors, the inclusion of anti-IgG₁, but not anti-IgG₂,-IgG₃, or -IgG₄, antiserum resulted in thein vitro inhibition of IgG-Tet synthesis. The magnitude of this inhibition was similar to that induced by treatment of the B cells with tetanus toxoid antigen. When the supernatants from normalin vitro cultures were assayed for IgG-Tet of the various IgG subclasses, it was observed that the IgG-Tet were almost exclusively IgG₁. Similar results were obtained when serum IgG-Tet were measured. Thus, IgG₁ appears to be the major subclass for (1) thein vivo-produced IgG-Tet, (2) thein vitro-produced IgG-Tet, and (3) the membrane receptor which can selectively convey an inhibitory signal to the IgG-Tet B cell.