CD38 expression, although a correlate of apoptosis, does not explain on its own the selective apoptosis of HIV-specific CD8⁺ T cells. (A) The correlation between the percentage (%) of spontaneous, anti-CD95/Fas–induced, and treatment-specific CD8⁺ T-cell apoptosis and ex vivo percentages (%) of CD38⁺ cells (top left, middle, and right panels, respectively) in total CD8⁺ T cells from HIV⁺ patients (n = 21). (B) Representative flow cytometry showing HIV-specific and CD8⁺ T cells from an HIV⁺ patient. Histograms depict CD38 levels and annexin V positivity in HIV-specific CD8⁺ T cells after culturing PBMCs for 14 hours in the absence or presence of anti-CD95/Fas antibody. (C) Pooled data presenting annexin V positivity in CD38⁺ and CD38⁻ HIV-specific (n = 6) and CMV-specific (n = 7) CD8⁺ T cells from HIV⁺ patients. Open symbols represent CD38⁺ whereas closed ones represent CD38⁻CD8⁺ T cells. (D) Pooled data showing the ex vivo MFI of Bcl-2 staining for CD38⁺ and CD38⁻ HIV-specific (triangles; n = 8), CMV-specific (diamonds; n = 13), and total CD8⁺ T cells from HIV⁺ patients (circles; n = 30) and healthy donors (squares; n = 9). Horizontal lines depict mean values. The P values were calculated using Student t test.