KEGG results indicated that co-expressed genes of CYP27A1 significantly enriched in the intestinal immune network for IgA production, rheumatoid arthritis, cell adhesion molecules, inflammatory bowel disease, complement and coagulation cascades, natural killer cell-mediated cytotoxicity, cytokine-cytokine receptor interaction, etc. (Fig. 7B). Here, CYP27A1 is linked to rheumatoid arthritis.