To induce GvHD, we used MHC-mismatched donors and recipients, with T cell-depleted bone marrow (TCDBM) from WT mice, donor CD4 T cells from either C57BL/6 (B6) WT or TCF-1 cKO mice (MHC haplotype b), and lethally irradiated BALB/c (MHC haplotype d) mice as recipients. Here, CD4 is linked to graft versus host disease.