RAG2 and Arthritis: Rag2−/− BM-transferred x-irradiated Csf2−/−Rag2−/− mice and Csf2−/−Rag2−/− BM-transferred x-irradiated Rag2−/− mice, in which GM-CSF production was restricted to ILCs or radio-resistant stromal cells including FLSs, respectively, developed significantly less severe arthritis than Rag2−/− BM-transferred x-irradiated Rag2−/− mice, in which both ILCs and radio-resistant stromal cells produced GM-CSF (Figure 5B).