Expansion of CD94/NKG2C⁺ cells in PBLs from HCMV-positive donors. Blood donors were classified in 2 groups (HCMV-positive and HCMV-negative) according to the detection of circulating HCMV-specific IgG; PBL samples were analyzed as described (Figure 1). (A-B) The proportions of NKG2A⁺ (Z199⁺) and NKG2C⁺ (p25⁺Z199^-) cells detected in total PBLs, as well as in gated CD3⁺ and CD3^- subsets, from 68 different individuals are shown (mean ± SEM). (C) The percentage of NK cells (CD3^-CD56⁺) expressing NKG2A or NKG2C in PBLs from 21 HCMV-positive and HCMV-negative donors are displayed (mean ± SEM). Statistical analysis was carried out as described in “Patients, materials, and methods”; ^***P < .001.