Analysis of Nfil3-deficient mice has identified a key role for Nfil3 in the development of natural killer (NK) cells,6 with similar functions in other innate lymphoid cells,7 and the CD8α+ dendritic cell subset.8 Within T cells, Nfil3 enhances the Th2 lineage9 while suppressing the Th17 lineage.10 The net effect of these changes is the spontaneous development of colitis, a process dependent on microflora and T cell activation.11 Less is known about the function of NFIL3 in humans. This evidence concerns the gene NFIL3 and colitis.