Suppression of immune responses to sheep red cell antigens in rats preimmunized with heterophilic antigen: cellular events.

Abstract

Depression of humoral immune response to sheep red cells (SRC) has been observed in rats previously immunized with heterophilic (Forssman) antigen. Analogous phenomena were observed by assay of splenic plaque-forming cells obtained from rats immunized in vivo with heterophilic antigen (HA) and challenged with SRC. Isophilic immune responses were almost completely suppressed. Kinetics of the primary and secondary immune responses were analyzed. Intervals of two to four days between administration of HA and SRC yielded maximal suppression. Primary immune responses to SRC were determined in cultures of splenic cell suspensions derived from rats which had been either injected in vivo with HA or received no treatment. Under these conditions, too, administration of HA interfered with the antibody responses to SRC. Both adherent and nonadherent cells caused inhibition, with this property appearing earlier in adherent than in nonadherent cells. A hypothesis, capable of explaining the observations made in this study and compatible with similar phenomena described in other systems, has been proposed according to which after immunization with HA, SRC are diverted to HA-stimulated cells which are not equipped to deal with the antigen complex represented by SRC.