Suppressive effect of graft versus host reactions on the immune response to heterologous red cells.

Graft versus host (GVH) reactions induced by the inoculation of parental spleen cells into adult untreated F recipients caused a marked suppression of the cellular and humoral immune response to sheep red cells (SRBC) and lipopolysaccharide, provided the GVH reaction was induced 7 days before immunization with SRBC. Adoptive transfer of parental or F spleen cells mixed with SRBC into irradiated F recipients, which had been subjected to a GVH reaction for 7 days, resulted in marked suppression of cellular antibody synthesis to both antigens. When the GVH reaction was induced by parental spleen cells from donors immunized to SRBC and the immune response to SRBC tested after 7 days, a marked suppression of cellular antibody synthesis occurred when the parental cells were of -2 genotype, but not if they were of -2 or -2 genotypes. The number of antigen-sensitive cells of parental genotype sensitive to SRBC in animals being subjected to a GVH reaction for 7 days was unaffected when the donors were of -2 or -2 genotypes, but decreased when the donors were -2. The number of antigen-sensitive cells of F genotype was only slightly decreased by a GVH reaction. It is suggested that the suppressive effect of a GVH reaction on antibody synthesis to other antigens represents an example of antigenic competition. This phenomenon would be caused by suppressed proliferation of immunocompetent cells of bone-marrow origin and not by competition for pluripotent antigen-sensitive cells. This suppression would be mediated by antigen stimulated thymus-derived lymphocytes.