Phenotype of the CD4⁺CD25⁺ and CD4⁺CD25^– T-cell subsets in HIV-infected patients. The membrane or intracellular (CTLA-4) expression of the different molecules was determined in whole blood cells by 4-color direct flow cytometry after successively combining the forward scatter/side scatter (FSC/SSC), CD3⁺, CD4⁺, and CD25 gates. Analysis was performed on CD25⁺ (▪) and CD25^– (□) T cells. Data from 15 patients studied are presented as mean percent positive cells ± SD (*P < .05).