Lymphotoxin-β receptor-independent development of intestinal IL-22-producing NKp46+ innate lymphoid cells.

The natural cytotoxicity receptor NKp46 is an activating receptor expressed by several distinct innate lymphoid cell (ILC) subsets, including NK cells, some γδ T cells and intestinal RORγt(+) IL-22(+) cells (NCR22 cells, IL-22-producing NKp46(+) cell). NCR22 cells may play a role in mucosal barrier function through IL-22-mediated production of anti-bacterial peptides from intestinal epithelial cells. Previous studies identified a predominant proportion of NCR22 cells in gut cryptopatches (CP), lymphoid structures that are strategically positioned to collect and integrate signals from luminal microbes; however, whether CP or other lymphoid structures condition NCR22 cell differentiation is not known. Programmed and inducible lymphoid tissue development requires cell-surface-expressed lymphotoxin (LT)α(1) β(2) heterotrimers (provided by lymphoid tissue inducer (LTi) cells) to signal lymphotoxin-β receptor (LTR)(+) stromal cells. Here, we analyzed NCR22 cells in LTβR-deficient Ncr1(GFP/+) mice that lack organized secondary lymphoid tissues. We found that NCR22 cells develop in the absence of LTβR, become functionally competent and localize to the lamina propria under steady-state conditions. Following infection of LTβR(-/-) mice with the Gram-negative pathogen Citrobacter rodentium, IL-22 production from NCR22 cells was not affected. These results indicate that organized lymphoid tissue structures are not critical for the generation of an intact and fully functional intestinal NCR22 cell compartment.