The retinoic acid-metabolizing enzyme Cyp26b1 regulates CD4 T cell differentiation and function

The vitamin A metabolite retinoic acid (RA) has potent immunomodulatory properties that affect T cell differentiation, migration and function. However, the precise role of RA metabolism in T cells remains unclear. Catabolism of RA is mediated by the Cyp26 family of cytochrome P450 oxidases. We examined the role of Cyp26b1, the T cell-specific family member, in CD4⁺T cells. Mice with a conditional knockout of Cyp26b1 in T cells (Cyp26b1−^/− mice) displayed normal lymphoid development but showed an increased sensitivity to serum retinoids, which led to increased differentiation under both inducible regulatory T (iT_reg) cell- and T_H17 cell-polarizing conditions in vitro. Further, Cyp26b1 expression was differentially regulated in iT_reg and T_H17 cells. Transfer of naïve Cyp26b1−^/− CD4⁺ T cells into Rag1−^/− mice resulted in significantly reduced disease in a model of T cell-dependent colitis. Our results show that T cell-specific expression of Cyp26b1 is required for the development of T cell-mediated colitis and may be applicable to the development of therapeutics that target Cyp26b1 for the treatment of inflammatory bowel disease.