In our experiments, the severity of T-cell transfer-induced colitis did not differ between Rag1−/− mice and RAG1−/− mice that had been backcrossed onto an β2i/MECL-1&β5i/LMP7-deficient background (Figure 1), arguing against a role for immunosubunit expression in the inflamed gut in colitis development. The gene discussed is RAG1; the disease is colitis.