To evaluate the effect of IL-21 on GVHD, we next supplemented the BM graft with mature RAG2p-GFP-derived allogeneic T cells (donor lymphocyte infusion (DLI)) and found that PBS-treated animals became ill as of the 3rd week post-BMT with a 50% survival rate (Fig. 5a) according to weight loss assessment (Fig. 5b). The gene discussed is IL21; the disease is graft versus host disease.