Passive transfer of antibody across the placenta or in milk has been thought to have a regulatory effect on the immune responsiveness of young animals. The effect of maternal antibody against rat male accessory glands (MRAG) on the systemic autoimmune responses of rat kits was studied. Serum obtained during the nursing period from female rats immunized with 5 mg/0.5 ml of MRAG or human serum albumin (HSA) emulsified in Freund's complete adjuvant before and during pregnancy contained anti-MRAG or anti-HSA, respectively. Kits born to MRAG-immunized dams were intradermally immunized with 5 mg/0.5 ml of MRAG-CFA at 21 and 51 days of age. Control kits from dams immunized with 5 mg/0.5 ml of human serum albumin emulsified in Freund's complete adjuvant (HSA-FCA) were similarly immunized with MRAG-FCA. Delayed-type hypersensitivity (DTH) studied 13 days after immunization with MRAG given at 21 days of age was significantly reduced only in the male kits born to MRAG-immunized dams compared with that of male kits from HSA-immunized dams (P less than 0.005). This hyporesponsiveness was not found in female kits from dams immunized with MRAG-FCA. The titre of circulating anti-MRAG studied at 65 days of age in kits born to MRAG-immunized dams approximated that in control kits. Antibodies against MRAG passively acquired from MRAG-immunized mothers did not alter the humoral autoimmune response of their kits.
