Attributes of circulating CD34⁺ HPCs. (A) Representative examples of CD34 and CD45 staining to identify HPCs in PBMC samples. (B) Absolute counts of CD34⁺ CD45^low Lin⁻ cells in middle aged (M; n = 27) or old (O; n = 26) adults, and in treatment-naive HIV-1–infected patients, grouped according to CD4⁺ T-cell counts: > 500 CD4⁺ (H; n = 35), between 200 and 500 CD4⁺ (I; n = 44), or < 200 (L; n = 23) CD4⁺ T cells/μL. (C) Correlation between CD34⁺ HPC and CD4⁺ T-cell counts in treatment-naive HIV-1–infected patients. The Spearman rank test was used to determine the correlation. (D) Numbers of total or white (CFU-GM and CFU-GEMM) progenitor CFUs generated from CD34⁺-sorted cells of HIV-1–infected patients and healthy donors. (E) Representative stainings for CD117, CD45RA, and CD10 on CD34⁺-sorted cells from PBMCs of HIV-1–infected patients and healthy controls. Numbers indicate percentages of cells in the different quadrants. (F) Ratio lymphoid (CD38⁺ CD117⁻ CD45RA⁺ CD10⁺) versus myeloid (CD38⁺ CD117⁺ CD45RA⁻ CD10⁻) HPCs within CD34⁺ cells from PBMCs of HIV-1–infected patients and healthy controls. (G) Frequency of lymphoid HPCs in the blood of HIV-1–infected patients and healthy controls. The Mann-Whitney or Kruskal-Wallis tests were used for comparing 2 groups or ≥ 3 groups, respectively. *P < .05, **P < .01, and ***P < .001. Bars indicate the median.