ECP-treated cells reduce GVHD and mortality after allogeneic BMT. (A) Survival and clinical GVHD scores after BMT. C3H.SW mice received syngeneic (C3H.SW; □, n = 15) or allogeneic (B6-Ly5.2) BM transplant followed by 4 weekly infusions of diluent (♦, n = 26) or of B6→C3H.SW splenocytes that were untreated (▵, n = 19) or treated with ECP (, n = 34); versus ▵ or ♦, *P < .004. (B) Histopathology scores 56 days after BMT (n = 8-20 per group); ▩ versus ▨, *P < .03. (C) Spleen reconstitution with donor lymphocytes (B6-Ly5.2) 56 days after BMT (n = 6-8 per group); ▩ versus ■, *P < .02. (D) Survival and clinical GVHD scores after haploidentical BMT. B6D2F1 mice received syngeneic (B6D2F1; □, n = 6) or allogeneic (B6-Ly5.2) BMT followed by 4 weekly infusions of diluent (♦, n = 18) or of B6→B6D2F1 splenocytes that were treated with ECP (, n = 13); versus ♦, *P < .02. Data are means (± SD) pooled from at least 2 independent experiments.