Inhibition of immune responses to sheep red cells in rats pre-immunized with heterophilic antigen.

After immunization of rats with heterophilic antigen (boiled homogenates of guinea-pig kidney), their immune responses to sheep red cells were consistently depressed, whereas those to heterophilic antigen were increased, as compared with controls. The suppression of immune responses to sheep red cells in rats immunized with heterophilic antigen may represent an animal model paralleling the interference with Rh immunization of ABO incompatibility in man. Experiments intended to elucidate the mechanism of this interference included simultaneous administration of sheep red cells and heterophilic antigen; comparison of antibody formation in intact and splenectomized rats; and passive immunization with isophilic and/or heterophilic antibodies prior to challenge with sheep red cells. On the basis of the experimental observations, a hypothesis was proposed according to which cellular diversion of antigen may be responsible for these inhibitions of immune responses.