Loss of HIV-specific CD4⁺ T cells and progression to AIDS despite high levels of HIV-specific cytokine-producing CD4⁺ T cells early in infection. Representative FACS plots showing the lymphocyte gate (A), gating of the CD3⁺CD4⁺ T cells (B), production of IFNγ and IL-2 of CD3⁺CD4⁺ T cells in the absence of stimulus (C,G), after stimulation with a Gag-peptide pool (D,H), CMV lysate (E,I), and PMA/ionomycin as a positive control (F,J). Percentages of cytokine-producing CD3⁺CD4⁺ T cells are indicated. Results of HIV-specific single IFNγ⁺ CD4⁺ T cells, single IL-2⁺ CD4⁺ T cells, and IL-2⁺ and IFNγ⁺ CD4⁺ T cells are summarized in box plots and depicted in panels K to M. CMV-specific single IFNγ⁺ CD4⁺ T cells, single IL-2⁺ CD4⁺ T cells, and IL-2⁺ and IFNγ⁺ CD4⁺ T cells are summarized in panels N to P. Each box summarizes results of 6 LTAs (gray) or 7 progressors (white). The horizontal bar represents the median, the box length represents the interquartile range, and the error bars show the outliers.