Suppression of the mixed leukocyte response and of graft-vs-host disease by spleen cells following total lymphoid irradiation (TLI).

Total lymphoid irradiation (TLI) was administered to mice as 17 fractions of 200 rads delivered to the major lymphoid organs. Spleen cells capable of suppressing the in vitro mixed leukocyte response (MLR) and in vivo graft-vs-host disease (GVHD) were found in mice after treatment with TLI. Suppression was not antigen specific and was markedly reduced by treatment of the spleen cells with anti-Thy-1.2 antiserum and complement. Suppressor activity declined with time after irradiation and disappeared within 30 to 40 days. The evidence suggests that the suppressor cells may prevent initial BM rejection and acute GVHD in allogeneic BM transplant recipients prepared with TLI.