KLRC2 and viral infectious disease: The reduced frequency of viral STIs in high-risk MSM could, potentially, be explained by this phenomenon, where CD57+/NKG2Chigh NK cells, activated through NKG2C by HLA-E, induce a strong antiviral response mediated by CD57+/NKG2Chigh NK cells that can protect these individuals against a variety of viral infections, including HIV.