Recently, the repertoire of cells that produce key cytokines implicated in IBD pathogenesis, such as interferon-γ (IFN-γ) and interleukin-17A (IL-17A), has been extended to include a population of cells termed innate lymphoid cells (ILCs) (Buonocore et al., 2010; Takatori et al., 2009). Here, IL17A is linked to inflammatory bowel disease.