Antibody mediated regulation of immune responses. I. Enhancement of specific antibody responses through IgM antibodies.

Injection of monoclonal IgM antibodies to sheep red blood cells (SRBC) 2 h before immunization with a low dose of antigen (Ag) specifically enhances the direct and indirect plaque-forming cell response. This enhancement was specific: the specific antigen had to be present; the plaque-forming cell (PFC) response to TNP-Ficoll- or bromelein-treated mouse red blood cells was not enhanced; the PFC response to SRBC was not enhanced by injections of monoclonal antibody to TNP. The optimum conditions for enhancement were found to be dependent on both the dose and the time of administration of antibody in relation to antigen. The possible mechanisms for this enhanced antibody response are discussed.