Figure 1.

Surface expression of HLA-DR is stably detected in variable proportions of circulating NKG2C+ adaptive NK cells in the absence of activation markers. NKG2C and HLA-DR expression was analyzed by flow cytometry in circulating NK cells from seronegative (n = 5; HCMV–) and seropositive (HCMV+) individuals with (n = 8; NKG2C^bright) or without (n = 7; NKG2C^dim) NKG2C+ adaptive NK cells. (A) Representative dot plots of NKG2C and HLA-DR expression in CD56^dim NK cells from HCMV- and HCMV+ individuals. Inset numbers indicate proportions of HLA-DR+ in CD56^bright and CD56^dim gates. (B) Percentage of NKG2C+ and HLA-DR+ cells in CD56^dim and CD56^bright NK cell subsets in individuals categorized according to their HCMV serology and the presence (NKG2C^bright) or absence (NKG2C^dim) of NKG2C+ adaptive NK cells. (C) Dot plots showing NKG2C and HLA-DR phenotype along time in two out of five HCMV+ individuals analyzed. Inset numbers indicate frequencies of HLA-DR+ cells in NKG2C+ and NKG2C- NK cells. (D) HLA-DR, CD25, and CD69 expression on circulating CD56^dim NK cells from HCMV+ individuals with NKG2C+ adaptive NK cells (mean ± SEM, n = 6) (*p < 0.05, **p < 0.01, ***p < 0.001).