IRF4 deficiency can confer resistance to Th17-related autoimmune diseases due to defects in Th17 cell differentiation.247,249,250 While IRF4 is not essential for Treg production, it is associated with Treg effector functions.244 Treg cells express high levels of IRF4, which can inhibit Th2 cell activity by regulating specific transcriptional programs within Treg cells.251 IRF5 appears to act as a positive regulator in Th17 differentiation. The gene discussed is IRF4; the disease is autoimmune disease.