Inhibition of immunological memory and T-independent humoral responses by monoclonal antibodies specific for murine complement receptors.

The importance of the complement system for mounting an antibody response in vivo was investigated by down-regulating and blocking the complement receptors (CR) in mice with three different monoclonal rat antibodies (mAb): mAb 8C12 recognized the C3b-binding site of CR1, mAb 7G6 recognized another site of CR1 and the C3d-binding site of CR2 and mAb 7E9 again recognized other epitopes on CR1 and CR2. We have earlier shown that 7G6, is the only mAb that completely suppresses the primary antibody response to horse erythrocytes. This antibody was also shown to suppress induction of immunological memory and a secondary antibody response. In contrast to what seems to be the case for thymus-dependent antibody responses, all three mAb could inhibit the antibody response to a thymus-independent antigen, dextran B 1355S.