FasL⁺ allogeneic CD4⁺ T cells play a major role in BM GVHD. [B6→BDF₁] transplantation model using combinations of donor BM and spleen cells with different Fas or FasL genotype. In panel B, groups are labeled as source of BM/source of SPL on the flow cytometric representations and — indicates no splenic cells. Values represent mean and SE (n = 3-6). Experiments were performed at least twice. (A-B) Flow cytometric analysis of B220⁺ and IgM⁺ cells. (C) Body weight change. (D) Numbers of splenic CD4⁺ and CD8⁺ cells.