Intriguingly, unlike allogeneic CD4+ or CD8+ T cells which cause severe GVHD [29], infusion of purified (Fig. S1) B6.lpr DN T cells pre-activated by alloantigen in vivo did not cause significant illness or mortality in lethally irradiated CB6F1 mice reconstituted with B6 (H-2b) BM (BM+DN, Fig. 1B–C). Here, CD8A is linked to graft versus host disease.