Loss of Gas6 conferred protection from lethal acute GVHD. Bone marrow isolated from donor mice was T cell–depleted. Each lethally irradiated recipient mouse (Balb/C, H-2^d) with a wild-type (WT) or Gas6^−/− genotype received 5 × 10⁶ T cell–depleted BMCs from a pool of full MHC-mismatched WT donors (C57BL/6, H-2^b). We infused 0.5 × 10⁶ WT splenic donor T cells to WT or Gas6^−/− recipient mice. (A) Kaplan-Meier plots of the survival of WT and Gas6^−/− mice. Survival after lethal acute graft-versus-host disease (GVHD) was improved in Gas6^−/− mice compared with WT mice (log-rank test, n = 10 and 13, respectively, P > .017). (B) Clinical signs of GVHD scored daily after transplantation according to Cooke et al.¹⁹  A score of 3 was assigned to mice that died in the course of the experiment. Two-way analysis of variance for repeated measures; n = 13 for WT and 10 for Gas6^−/−, P = .012; followed by Bonferroni post tests for specific time points, **P < .01, ***P < .001.