RAG2 and dermatitis: To evaluate pathogenicity of Dsg3H1-Rag2−/− CD4+ T cells, Dsg3H1-Rag2−/− CD4+ T cells that had developed without undergoing Dsg3-specific negative selection in Dsg3−/− mice were isolated from peripheral lymph nodes (LNs) or spleen (Sp) and transferred to Rag2−/− immunodeficient mice; subsequently, Dsg3H1-Rag2−/− CD4+ T cells proliferated under lymphopenic conditions, and the recipients developed skin inflammation pathologically classified as interface dermatitis (Fig. 1C).