Damage control: Rorγt+ innate lymphoid cells in tissue regeneration.

Innate lymphoid cells (ILC) function at the crossroads of innate and adaptive immunity. ILC expressing Rorγt are involved in lymphoid organ formation during embryonic development and mucosal homeostasis and immunity after birth in both mice and man. Mucosal ILC can express natural cytotoxicity receptors NKp44 and NKp46 and produce IL-22, a cytokine pivotal in the control of epithelial innate defenses. The requirements for mouse Rorγt+ ILC development are well charted and in recent years factors involved in differentiation of human ILC have also been identified. In this review we will focus on recent observations that uncovered Rorγt+ ILC as mediators of epithelial tissue regeneration after radiation-induced damage.