Loss of T cell microRNA provides systemic protection against autoimmune pathology in mice

► MicroRNA are required to potentiate T cell activation and Th1 effector expansion. ► Excision of Dicer results in profound inhibition of T cell activation. ► The anti-autoimmune function of T cell microRNA is restricted to pathology of the colon. ► A pro-autoimmune function of T cell microRNA is observed systemically. ► Reduction of Dicer within T cells has the potential to mitigate Th1 autoimmunity.