Innate lymphoid cells in homeostasis, infection, chronic inflammation and tumors of the gastrointestinal tract

Purpose of Review: To highlight the functions of a recently discovered group of immune cells known as innate lymphoid cells (ILCs) during homeostasis and infections of the gastrointestinal tract. Recent Findings: ILCs are lymphocytes that lack specific antigen receptors. They are found in the mucosae and mucosal-associated lymphoid tissues, where they promptly initiate cytokine responses to pathogens upon initial exposure. ILCs have been classified into distinct groups based on their cytokine secretion: ILC1 produce IFN-γ, ILC2 secrete IL-5 and IL-13, and ILC3 produce IL-22 and IL-17. Recent studies have discovered the heterogeneity of ILC1 and ILC3 in the gastrointestinal tract. ILC1 subsets may contribute to the inflammatory bowel disease. ILC3 subsets may be beneficial in the defense against gastrointestinal infections, but their sustained activation may lead to cancer. Summary: ILCs may provide a target for new avenues of therapeutic intervention in inflammatory bowel disease and gastrointestinal cancer.