To test the role of the individual Crk proteins in GvHD pathology, lethally irradiated BALB/c mice were injected with T-cell depleted C57BL/6 bone marrow (TCDBM) along with CD8+ T cells from WT, DKO, CrkI/II KO, or CrkL KO C57BL/6 mice. This evidence concerns the gene CD8A and graft versus host disease.