Feedback regulation of immune responses by immune complexes; possible involvement of a suppressive lymphokine by FcR gamma-bearing B cell.

Inoculations of antigen-antibody complexes (immune complexes) with the intact Fc portion generates suppressor cells in vivo by binding to FcR gamma on B cells via Fc portions. The cell type responsible for the suppression appears to be B cells bearing FcR gamma. Neither T cells nor macrophages participate in both the inductive and effective phases of this type of regulation. The suppression caused by splenic B cells, previously stimulated with immune complexes in vivo, is mediated by humoral factor(s) released from them. The suppressive factor(s) have H-2 gene product(s) coded by the right-hand side of the H-2 gene complex, but not for FcR gamma themselves or immunoglobulins. It has shared component(s) with suppressive B cell factor (SBF) released from FcR gamma + B cells stimulated with immune complexes in vitro, and it resembles SBF in its mode of action. These findings indicate that immune complexes, the final products of antibody responses, control the immune responses by stimulating surface FcR gamma on B cells. It is of interest that this type of regulation functions in vivo.