For instance, a reduction of absolute NK cell numbers was found in HIV(+) as well as in HCV(+) patients[16,17] and both HIV and HCV mono-infection as well as HIV/HCV co-infection have been observed to be associated with the appearance of a highly dysfunctional subset of CD56- CD16+ NK cells, characterized by a poor cytotoxic activity[18–23]. This evidence concerns the gene NCAM1 and coinfection.