KGF reduces GVHD mortality and morbidity in allogeneic BMT. Recipients were transplanted with 5 × 10⁶ bone marrow cells and 0.5 × 10⁶ splenic T cells from allogeneic (B6) or syngeneic (B6D2F1) donors after 1,550 cGy of TBI. KGF (Amgen) or control diluent was given subcutaneously from either day -3 to day 0 or day -3 to +7. Syngeneic BMT (n = 22, - - - ), control diluent-treated allogeneic BMT (n = 26, - · · - ), KGF-treated (day - 3 to 0) allogeneic BMT (n = 16, ), KGF-treated (day -3 to +7) allogeneic BMT (n = 18, ). (A) Survival. Control-treated allogeneic BMT recipients versus KGF-treated (both treatment schedules) and syngeneic BMT recipients (P < .01 by Mantel Cox logrank test). (B) GVHD clinical score. Animals were scored for clinical GVHD by five parameters as described in Materials and Methods. GVHD severity (mean ± standard error [SE]) was significantly less in animals receiving KGF from day -3 to +7 than those receiving KGF from day -3 to 0 and control-treated animals from day 21 onwards (P < .05) and significantly higher than in syngeneic BMT recipients (P < .05). Data represent results combined from two similar experiments.