expression. NK cells are cytotoxic cells, circulating in the bloodstream, killing virus-infected, and tumor cells. ILC1s, are non- cytotoxic or weakly cytotoxic, tissue resident cells, functioning in the defence against infections with viruses and certain bacteria.

Due to ILC1s and NK cells having both shared and unshared features, the classification of human ILC1s has been problematic. Both cell types produce IFN-?