Roles of RORγt+ innate lymphoid cells in mucosal tissues of mouse and human

Innate Lymphoid cells (ILCs) are recently defined lymphocytes composed of several subsets such as Natural Killer (NK), Natural Helper (NH) and RORγt(+) cells, which have no antigen receptors but exhibit rapid cytokine production after stimulation. Murine RORγt(+) ILCs can be classified either as CCR6(+)c-kit(high)IL-7Rα(high) or CCR6NK(-)p46(+) cells. The former ones play roles on the formation of secondary lymphoid tissues and the later ones contribute to the maintenance of intestinal epithelial integrity by producing IL-22. Human fetal intestine, tonsil and lympho nodes harbor both NKp44 positive and negative RORγt(+) ILC subsets. Since human Crohn's disease patients have increased number of RORγt(+) ILCs in the inflamed intestine, roles of RORγt(+) ILCs on the pathogenesis of Crohn's disease became of great interest.