The percentage of PD-1 and PD-L1 expressing Treg cells is increased in HIV-infected individuals.

(A) A representative flow cytometry dot plot from an HIV-infected individual with <500 CD4/μL and >2000 viral RNA copies/mL blood showing the gating of effector Treg cells (eTreg: CD4+CD45RA-FOXP3hi) and resting Treg cells (rTreg: CD4+CD45RA+FOXP3lo) from a previously gated CD4 T cell population. Numbers indicate percentages of each population. (B) Percentages of PD-1+ (left panel) and PD-L1+ (right panel) Treg (including eTreg and rTreg), eTreg and rTreg cell populations in HIV-infected individuals (black circles) and healthy, uninfected controls (empty triangles). The mean ± SEM (standard error of the mean) is shown. Significant differences were determined by a Mann-Whitney U test and indicated by asterisks (*p <0.05; **p <0.01; ***p <0.001; ns: non significant). (C) Correlation between PD-1 expression and PD-L1 expression on Treg cells from HIV-infected individuals. The Spearman’s rank correlation coefficient (r) and the p value (P) are indicated. (D) Expression of PD-1 (left panel) and PD-L1 (right panel) in healthy control’s PBMC exposed to HIV-1 Bal (black bars) at 0.3 multiplicity of infection, compared with mock control (white bars). Bars represent the mean ± SEM (standard error of the mean) from 3 independent experiments with 7 different donors. Significant differences were determined by Wilcoxon matched pairs test and indicated by asterisk (*p <0.05). ns, non significant.