CD4 T cells in PB of HIV-infected patients are skewed toward a Th1 phenotype. PB lymphocytes from cohorts of HIV-infected (●) and uninfected persons (○) were stimulated with anti-CD3 overnight in the presence of brefeldin A and stained as in Figure 1. The frequency of memory CD27⁺ (A) and CD27⁻ (B) CD4 T cells that produced IL-17 or IFN-γ was then measured by flow cytometry. The ratio of IL-17–producing cells to IFN-γ–producing cells was then compared within both memory CD27⁻ and CD27⁺ CD4 T-cell subsets from HIV⁻ (C, ○) and HIV⁺ (D, ○) patients. Statistical significance was determined by the Mann-Whitney test.