Changes in cell-surface phenotypes of CD4⁺ T cells during primary HIV-1 infection. Flow cytometry histograms, gated on CD3⁺CD4⁺ T cells, show increases in (A) CCR5⁺CD38⁺⁺⁺; (B) CCR5⁺TIA-1⁺Ki-67⁺; (C) perforin⁺granzyme B⁺; and (D) CD127^– CD57^– T cells from representative early PHI patients and HIV^– controls. Subpopulations in quadrants are shown as percentages of CD3⁺CD4⁺ (A, C, D) or CD3⁺CD4⁺Ki-67⁺ (B) cells. Results from all patients and controls are summarized in panel E. Box plots show 10th, 25th, median, 75th, and 90th percentiles for each marker for each cohort.