Analysis of functionally distinct populations of virus-specific CD4 T cells. (A) Flow cytometry profiles of the distribution of blood HIV-1- and CMV-specific CD4 T cells within IL-2-, IFN-γ-, and IFN-γ/IL-2-secreting cell populations in representative progressors, LTNPs, and HIV-negative subjects. The cluster of events shown in red correspond to the responder CD4 T cells, which express IL-2 and/or IFN-γ. (B) Mean ± SE of cumulative data on the proportion of HIV-1- and CMV-specific CD4 T cells within the different cytokine-secreting cell populations in progressors, LTNPs, and HIV-negative subjects.