Nfil3 is crucial for development of innate lymphoid cells and host protection against intestinal pathogens

The bZIP transcription factor Nfil3 (also known as E4BP4) is required for the development of natural killer (NK) cells and type 1 innate lymphoid cells (ILC1s). We find that Nfil3 plays a critical role in the development of other mucosal tissue-associated innate lymphocytes. Type 3 ILCs (ILC3s), including lymphoid tissue inducer (LTi)–like cells, are severely diminished in both numbers and function in Nfil3-deficient mice. Using mixed bone marrow chimeric mice, we demonstrate that Nfil3 is critical for normal development of gut-associated ILC3s in a cell-intrinsic manner. Furthermore, Nfil3 deficiency severely compromises intestinal innate immune defense against acute bacterial infection with Citrobacter rodentium and Clostridium difficile. Nfil3 deficiency resulted in a loss of the recently identified ILC precursor, yet conditional ablation of Nfil3 in the NKp46(+) ILC3 subset did not perturb ILC3 numbers, suggesting that Nfil3 is required early during ILC3 development but not for lineage maintenance. Lastly, a marked defect in type 2 ILCs (ILC2s) was also observed in the lungs and visceral adipose tissue of Nfil3-deficient mice, revealing a general requirement for Nfil3 in the development of all ILC lineages.