NCAM1 and HIV-1 infection: The classical description of NK cell phenotypes relies on CD56 and CD16 expression with the distinction of three broad phenotypes which include CD16+/−CD56bright cells representing a minority of circulating and the majority of tissue-associated NK cells, CD16+CD56dim cells that constitute the majority of circulating NK cells and are viewed as effectors cells, and CD16+CD56− exhausted NK cells that are poorly functional express low levels of natural cytotoxicity receptors (NCRs) and may become more abundant in PB during chronic infections, such as HIV-1 infection.