Inhibition of IgG-mediated immunosuppression by a monoclonal anti-Fc receptor antibody.

IgG-antibodies can efficiently suppress the antibody response against their specific antigen. The suppressive capacity is dependent on intact Fc regions. However, it is not clear which of the Fc-mediated effector functions are necessary for the induction of immunosuppression. The monoclonal antibody 24G2, which binds to murine Fc receptors on macrophages and B cells, was used in the present study to address the question of whether IgG-mediated suppression is in fact dependent on the binding of IgG antibodies to Fc receptors on splenocytes. In a murine in vitro immunization system, 24G2 is shown to reverse efficiently the suppression of the sheep erythrocyte-specific antibody response. The role of B cells or macrophages as effector cells is discussed.