This model has been criticized for frequent development of graft versus host disease (GvHD) symptoms affecting studies of innate immunity, yet recent models such as C57BL/6 RAG2 -/- common γ chain -/- CD47 -/- triple knockout mice present dramatically reduced risks of GvHD and improved reconstitution of human adaptive immune system (88). This evidence concerns the gene RAG2 and graft versus host disease.