Proliferation potency of CXCR1⁺ and CXCR1⁻ effector CD8⁺ T cells. (A) TCR engagement–induced proliferation of effector CD8⁺ T cells. The CXCR1⁺ and CXCR1⁻ subsets were sorted from healthy subject no. U-4. The CFSE-labeled sorted CD8⁺ T-cell subsets were analyzed for CFSE dilution profiles after 5 days of solid-phase anti-CD3 mAb stimulation with or without IL-2 (200 u/mL). The values in each histogram show the percentage of divided cells (CFSE^low) and undivided cells (CFSE^high). (B) Mean percentage and SD of CFSE^low and CFSE^high cells in each CD8⁺ T-cell subset after 5 days of anti-CD3 mAb stimulation from 4 individuals are shown. (C) Ag-driven proliferation of CXCR1⁺ and CXCR1⁻ effector subsets. The effector CXCR1⁺ and CXCR1⁻subsets were sorted from the HCMV-seropositive healthy subjects U-14 and U-1. The percentage of HCVM-tetramer⁺ CD8⁺ T cells in each subset before stimulation is as follows: U-14 total CD8⁺ T cells: 2.2%, CXCR1⁺ subset: 3.3%, CXCR1⁻ subset: 5.2%; U-1 total CD8⁺ T cells: 2.4%, CXCR1⁺ subset: 0.5%, and CXCR1⁻ subset: 1.3%. The CFSE-labeled sorted CD8⁺ T-cell subsets were cocultured for 5 days with irradiated C1R-A*0201 cells pulsed or not with HCMV-1 CTL epitope peptide. The percentages of divided HCMV-1-A*0201 tetramer⁺ (top left), divided tetramer⁻ (bottom left), undivided tetramer⁺ (top right), and undivided tetramer⁻ (bottom right) cells in each sorted subset are shown.