Mitigation of graft-versus-host disease in mice by treatment of donors with bacterial endotoxin.

Treatment of DBA/2 (H-2d) mice with bacterial endotoxin prior to transplantation of their spleen and lymph node cells into immunosuppressed AKR (H-2k) mice prevented acute mortality from graft-versus-host (GVH) disease. AKR mice that received immunocompetent cells from untreated DBA/2 mice had a median survival time (MST) of 13 days. In contrast, AKR mice that received immunocompetent cells from endotoxin-treated DBA/2 donors had an MST of 54 days. Endotoxin treatment of AKR recipients was not essential for preventing mortality from acute GVH disease. Chimerism was proved by demonstrating that the lymphoid cells of long-term surviving AKR mice had the characteristics of DBA/2 lymphoid cells as measured by their response in mixed leukocyte culture (MLC) tests. Spleen cells from endotoxin-treated DBA/2 mice were able to stimulate, and to be stimulated by, AKR spleen cells in MLC assays. Furthermore, spleen cells from endotoxin-treated DBA/2 mice did not suppress the responses of DBA/2 or AKR spleen cells in 'three-party' MLC tests.