CD8^low CD8 naive T cells from untreated HIV-infected subjects are functionally impaired with respect to IL-2 secretion after TCR stimulation. PBMCs from subjects in study D, including 16 Prog. CD < 350 and 10 HAART subjects, were stimulated or not by the superantigen SEB to determine IFNγ and IL-2 intracellular cytokine response. Cells were stimulated overnight and analyzed for cytokine secretion in combination with surface staining for CD3, CD4, CD8, CD45RA, CD27, CD28, and CCR7. (A) Ethidium monoazide (EMA) labeling was also used to discriminate live from dead cells. (B) The frequency of IL-2 but not IFNγ-responding cells was determined in naive CD8⁺ T cells (EMA⁻CD3⁺CD8⁺CD45RA⁺CD27⁺CCR7⁺CD28⁺). P values were calculated using Mann-Whitney test for group analysis as indicated by the horizontal bar.