The frequency of PD-1-expressing Treg cells correlates with markers of disease progression.

(A) Representative flow cytometry dot plots showing PD-1 gating on Treg cells (including eTreg and rTreg). One HIV-infected individual from each study group is displayed. Numbers indicate the percentage of PD-1+ Treg cells in PD-1 stained samples (down) compared with isotype control antibodies (up). (B) PD-1 expression on Treg cells from different HIV-infected study groups (black circles) and healthy controls (empty triangles) are shown as indicated. Each dot represents the result from one individual. The mean ± SEM (standard error of the mean) is shown. Significant differences were determined by a Mann-Whitney U test, corrected for multiple comparisons using Bonferroni method, and indicated by asterisks (*p <0.05; **p <0.01; ***p <0.001). (C) Correlation of PD-1 expression on Treg cells from HIV-infected individuals with viral loads (up) and CD4 T cell counts (down), respectively. Spearman’s rank correlation coefficients (r) and p values (P) are indicated.