Different cytokine productivity of CXCR1⁺ and CXCR1⁻ effector subsets among HCMV-specific CD8⁺ T cells. (A) Cytokine productivity of HCMV-specific effector CD8⁺ T cells. CXCR1⁺ and CXCR1⁻ cells in the CD27⁻CD28⁻CD8⁺ cell population were sorted from HCMV-seropositive healthy subject number U-14. Sorted cells were cocultured with C1R-A*0201 cells pulsed with HCMV-1 CTL epitope peptide for 6 hours, and then the frequency of cytokine-positive cells was determined by staining for intracellular cytokine. These cells were also stained with HCMV-tetramer in tubes separate from those used for the cytokine staining to detect the frequency of HCMV-specific CD8⁺ cells. The frequency of cytokine-producing cells in the total HCMV-specific cell population of each subset is shown as the percentage of cytokine-positive cells relative to the percentage of the HCMV-tetramer⁺ cell population (%/Tet). Nonspecific cytokine-positive cells (ie, cytokine-positive cells in the coculture of C1R-A*0201 cells without peptide) were subtracted from all data. (B) The mean percentage and SD of cells producing each type of cytokine in each HCMV-specific CD8⁺ T-cell subset from 3 HCMV-seropositive healthy subjects are shown.