Specific immunosuppression after peroral administration of antibodies

: The influence of immunization of lactating female rats with sheep red blood cells on the primary immune response of their progeny, and oral administration of heterologous antibodies, on the immune response of suckling rats was studied in experiments on 52 August rats. It was shown that oral antibody administration with breast milk and feeding with heterologous serum resulted in a drastic suppression of the splenic antibody-producing cells and in a fall of the humoral antibody titre in the suckling rats. The immunosuppression was reversible and could not be adoptively transferred. It is concluded that the antibodies entering the newborns' body with the mother's milk not only provide the passive immunity but also produce a regulatory effect on the immune system.