To confirm the expression of the IL-22 receptor IL-22Rα1 in the hippocampus, double immunofluorescence staining of IL-22Rα1 and Iba-1 was performed, and the results showed that IL-22Rα1 expression was increased in the hippocampus of DM model mice and that IL-22Rα1 was localized to Iba-1-expressing cells (Fig. 5d). The gene discussed is IL22RA1; the disease is diabetes mellitus.