NCR2 and neoplasm: Several studies have shown phenotypic and functional defects in NK cells from HIV-infected patients, including aberrant antibody-dependent cellular cytotoxicity; high expression of inhibitory natural killer receptors; low levels of activating receptors, including NKp30, NKp44, and NKp46 (37); and reduced tumor cytotoxicity (27, 29, 38, 39).