The gastrointestinal mucosa harbors diverse innate lymphoid cell (ILC) subsets that secrete specific cytokines early during the immune response. In Immunity, Fuchs et al. identify a subset of intraepithelial ILCs that are NKp44+CD103+ in humans and NKp46+NK1.1+CD160+ in mice and are distinct from classical NK cells, although they belong to the same group of ILC1 cells. These cells produce IFN-γ when stimulated with IL-12 and IL-15, can release lytic mediators, have an intraepithelial location and express markers consistent with TGF-β exposure and activation. In mice, they develop independently of IL-15 signaling, which confirms that they are not conventional NK cells. These cells are responsive to danger signals from epithelial and myeloid cells and proliferate in the small intestine epithelium in patients with Crohn's disease, which suggests that they may have a role in intestinal inflammation and immunopathology.

Immunity 38, 769–781 (2013)