In a series of experiments involving adoptive T cell transfer, chimeric mice, and the Rag1–/– mice where Brd4 was deleted in HFSCs, we demonstrated that deletion of Brd4 in the Rag1–/– hosts abrogated hair growth and regeneration without the induction of dermatitis, but adoptive transfer of γδ T cells into those mice readily capitulated dermatitis as observed in Brd4fl/fl Ox40-Cre mice. The gene discussed is RAG1; the disease is dermatitis.