Suppression of mouse IgE response by immune complexes

The effect of antibodies alone or complexed to antigen on an IgE response was compared in mice immunized with a low dose of antigen. The results demonstrated that immune complexes (ICs) at equivalence were more efficient than antibodies in promoting a suppression of this response when they were injected simultaneously or before, but not after, the antigen. This effect was dose dependent, antigen specific, and long lasting. Furthermore, only isologous ICs were suppressive. ICs prepared with IgG1 antibodies were more effective than ICs prepared with IgG2. Digestion of the Fc fragment of the antibody eliminated completely the suppressive action of antibodies alone, but not of ICs. These results indicate that, whereas an Fc-dependent mechanism is responsible for the effect of antibodies, an additional mechanism is also operating in suppression induced by ICs.