CMV-specific T-cell frequencies in healthy individuals.

(A) Dot plot of anti–IFN-γ–FITC fluorescence (x-axis, arbitrary units, log scale) versus CD69-PE fluorescence (y-axis, arbitrary units, log scale) of lymphocytes gated on positive CD4-APC fluorescence after incubation with CMV antigen. (B) Dot plot of anti–IFN-γ–FITC fluorescence (x-axis, arbitrary units, log scale) versus CD69-PE fluorescence (y-axis, arbitrary units, log scale) of lymphocytes gated on bright positive CD8-APC fluorescence after incubation with the HLA-A2–binding CMV-pp65 peptide NLVPMVATV. (C) NLVPMVATV-HLA-A2.1/tetramer-APC fluorescence (“tetramer,” x-axis, arbitrary units, log scale) versus CD8-PerCP fluorescence (y-axis, arbitrary units, log scale) of lymphocytes gated on forward scatter and side scatter parameters. (D) Correlation of the frequency of IFN-γ–producing CMV-specific CD4⁺ T cells (x-axis, percentage of CD4⁺ T cells) and IFN-γ–producing HLA-*0201 restricted CMVpp65_(NLVPMVATV)-specific CD8⁺ T cells (y-axis, percentage of CD8⁺ T cells) in HLA-A2⁺CMV-seropositive healthy individuals (n = 7). IFN-γ–producing CMV-specific CD4⁺ T-cell frequencies correlate with IFN-γ–producing CMV-specific CD8⁺ T cells (r = 0.7928, P = .0480).