RAG2 and graft versus host disease: In this paper, we show that HUMAMICE developed by backcrossing derived Sure-L1 mice with Rag2-/- mice, IL2rγ-/- mice and Perf-/- mice can be efficiently reconstitute with HLA-matched PBMCs without developing GvHD and with a functional immune system able to launch a robust human T cell-dependent response.