Evidence for Two Types of Non‐specific Suppressor Cells Activated by the Graft‐versus‐Host Reaction in Mice

Abstract

In vitro experiments were carried out to investigate the immunosuppressive efect of different populations of spleen cells obtained from animal experiencing a graft-versus-host reaction (GVHR). To induce the GVHR, parental lymphoid cells were injected into adult F1 hybrid mice. GVHR-activated spleen cells (GVH-sc) taken at different times post-GVHR induction were separated into adherent and non-adherent fractions and treated with anti-theta serum plus complement. The different types of GVH-SC were added to either parental (donor-type) of F1 (host-type) normal spleen cells and cultured with sheep erythrocytes in a modified Marbrook chamber. It was found that both adherent and non-adherent 10-day GVH-SC significantly inhibited the plaque-forming cell response of F1 normal spleen cells but not that of parental normal spleen cells. Significant suppression of the parental response was observed following the addition of 15-day GVH-SC or anti-theta treated adherent and non-adherent 7-day GVH-SC. The results suggest that the non-specific immunosuppressive effect of GVH-SC is mediated by GVHR-activated macrophages and B lymphocytes found in the anti-theta treated adherent and non-adherent fractions of the GVH-SC suspensions respectively.