Effects of Gas6 deficiency on acute lethal GVHD-associated histopathology. Lethally irradiated recipients from allogeneic T cell–depleted BMT that received 0.5 × 10⁶ WT splenic donor T cells were killed at day 6. (A) Flow cytometric analysis of recipient circulating cells on day 6. Left panel: B220-H-2^b double-positive cells gated to the mononuclear compartment; right panel: CD4⁺ cells gated to the H-2^b mononuclear compartment. No significant difference is shown between WT and Gas6^−/−. (B) Left panel: representative flow cytometric analysis of spleen cells on day 6. Right panel: donor lymphoid chimerism in the CD4⁺ or CD8⁺ splenic compartment of WT and Gas6^−/− recipient mice (n = 6 or 7; Student t test, P > .05). (C) Semiquantitative analysis of tissue pathology at day 6 after BMT according to Cooke et al¹⁹  and Hill et al²⁰  (Student t test, n = 6, ***P < .001).