PD-1 expression on HIV-specific CD8⁺ T cells is higher in TP patients than in LTNPs. (A) Frequencies of PD-1–expressing CD3⁺, CD4⁺, and CD8⁺ T cells in the 4 groups, including healthy controls (HCs), long-term nonprogressors (LTNPs), typical progressors (TPs), and complete responders to HAART (CRs). Case numbers for the 4 groups are the same as shown in Table 1. (B) The frequency and mean fluorescence intensity (MFI) of PD-1 molecules expressed on pentamer⁺ HIV-specific CD8⁺ T cells in TPs and LTNPs. Error bars indicate standard deviation. (C) Representative flow cytometric plots of PD-1–expressing virus-specific CD8⁺ T cells from LTNPs and TP patients showing different CD4 T-cell numbers (cells/μL) and viral loads (copies/mL). Values in the upper right quadrant represent the percentage of pentamer⁺CD8⁺ T cells that express PD-1. (D-E) Total and virus-specific CD8⁺ T cells that up-regulate PD-1 molecules are inversely correlated with CD4 T-cell numbers. (F-G) Total and virus-specific CD8⁺ T cells that express PD-1 are positively correlated with viral load. □ indicates LTNPs; ○, TP patients; solid line, linear growth trend; r, correlative coefficient. P values are shown.