KLRC2 and HIV-1 infection: Unexpectedly, the frequency of NKG2C+NK cells did not increase in the first and third months or after twelfth month after HIV-1 infection until reaching chronic HIV-1 infection over 2 years (Figure 4A, P = 0.005); the same situation was observed in NKG2A−NKG2C+NK subpopulation cells as shown in Figure 4B.