CD4 and HIV-1 infection: In healthy individuals, a median of 26% of total CD4+ T cells (interquartile range [IQR], 21 to 30%) expressed CD161, which was 1.5 times higher than the proportion in HIV-1-infected individuals not on ART (median, 16%; IQR, 12 to 22%) and 1.8 times higher than that in HIV-1-infected donors on ART (median, 14%; IQR, 11 to 17%) (Fig. 1A), suggesting that HIV-1 infection may deplete or downregulate CD161+ CD4+ T cells.