CD69 and neoplasm: The C-type lectin receptor CD69 represents an early activating marker and may play a direct role in mediating cytotoxicity against tumor target cells 41, whereas KLRG1 is a C-type lectin inhibitory receptor, expressed on a subset of mature NK cells that produce low levels of IFN-γ and have a slow in vivo turnover rate and low proliferative responsiveness to IL-15 42.