KLRK1 and colonic neoplasm: Human intestinal CD8αβ T-IEL spontaneously kill selected colon cancer cell lines that express even low levels of NKG2D ligands, by triggering FasL-mediated cytotoxicity.61 However, freshly isolated human T-IEL did not kill other cell lines when triggered with anti-NKG2D antibodies,55 suggesting that colon cancer cell lines express other factors that enhance their killing.