Repeated intraperitoneal injections of saline attenuate the antibody response to a subsequent intraperitoneal injection of antigen.

The results of two experiments with male C3H/HeJ mice indicated that repeated intraperitoneal (ip) injections of sterile saline over a 2-week period resulted in an attenuated antibody response to the subsequent ip injection of a soluble protein antigen, keyhole limpet hemocyanin. There were no differences among experimental groups that received a different number of preimmunization injections of saline, and comparable effects were obtained simply by the daily handling of mice. Neither repeated ip injections nor handling altered preimmunization (baseline) corticosterone levels, and only previously unmanipulated mice showed an elevation in corticosterone levels 30 min after ip immunization. These latter results suggest that the depressed IgM and IgG responses were not due to the immunosuppressive effects of endogenously elevated adrenocortical steroids.