IL-10Rα blockade restores HIV-specific CTL function in individuals with uncontrolled viremia. (A) Flow cytometry was used to assess proliferation of HIV-specific HLA class I tetramer–labeled CD8 T cells from 2 subjects incubated with the cognate HIV epitope, plus isotype control antibody or IL-10Rα blocking antibody. Representative data from 2 subjects is shown. Numbers in upper right quadrants indicate the percentage of CD3⁺CD8⁺Tetramer^high cells for each condition. (B) Statistical comparison of impact of IL-10Rα blockade on HIV p24–specific Tet⁺ CD8 T-cell proliferation in chronically HIV-infected subjects with undetectable viral loads (AVIR; n = 7), and chronically infected individuals with viral loads of greater than 1000 RNA copies/mm³ (VIR; n = 13) demonstrated a significant difference between these groups (P = .009; Mann-Whitney U test). The vertical axis (IL-10 proliferation index) corresponds to the ratio of the fraction of Tet⁺ cells (%CD3⁺CD8⁺Tet^high) cells in the presence of the IL-10Rα blocking antibody versus isotype control. Short horizontal bars indicate median proliferation index. (C) Statistical analysis of the data on subjects in panel B indicated a significant correlation between untreated viral load and the effect of IL-10Rα blockade on HIV-specific CD8 T-cell proliferation (R = 0.5445, P = .013; Spearman rank sum test).