Here, utilizing germ-free (GF) Il22-/- mice lacking the critical cytokine Il22 for an acute phase response and Rag1 knockout (Rag1-/-) mice lacking mature T and B lymphocytes in adaptive immune response, both of which are susceptible to CR infection under SPF condition, we assessed the impact of gut microbiota on the CR susceptibility. The gene discussed is RAG1; the disease is infection.