RÉSUMÉ
The mucosal tissues form the interface between the outside world and the sterile environment of the body.Innate immunity plays a critical role in the maintenance of mucosal homeostasis.Recently,a new subset of innate immune cells named NK-22 has been discovered to reside at tonsil and intestine both in human and mice.NK-22 cells share features with both natural killer (NK) cells and lymphoid tissue-inducing (LTi) cells.NK-22 cells express a variety of NK cell receptors and phenotypically resemble that of immature NK cells (iNKs).However,they are quite different from NK cells in function and development.NK-22 cells lack conventional NK cell cytotoxic function and produce IL-22 instead of IFN-?.It is currently considered that NK-22 cells are not a subset of NK cells.They develop from LTi cells and the development process depends on ROR?t and commensal microflora.NK-22 cells are involved in immune protection against the pathogen Citrobacter rodentium.The IL-22 secreted by NK-22 cells contributes to epithelial cell resistance to injury and mucosal tissue repair after microbial infection.