Ectonucleotidases CD39 and CD73 are expressed on the surface of regulatory T cells (Treg) and cleave ATP to immunosuppressive adenosine. CD39 could potentially serve as a new functional marker for Treg isolation. The frequency and absolute numbers of CD4+CD39+ T cells were determined in 32 HIV+ patients and in 10 healthy donors (HD). CD4+ T cells were negatively selected by magnetic beads PBMC. CD39+ Treg cells were then isolated by biotin-conjugated anti-CD39 Abs and anti-biotin magnetic beads. T cells were phenotyped by flow cytometry for CD39+, CD73+, FOXP3+, CCR4+, CD127neg, CD49dneg, and CD121a+. CFSE-based proliferation assays and ATP hydrolysis were used to measure Treg functions. Cytokine expression in CD4+CD39+ T cells was determined by Luminex. HIV-patients on and off anti-retroviral regimen had a significantly lower absolute number of CD39+CD25+ Treg and CD39+CD25neg T cells (p<0.05) than HD. The CD4+CD39+ T cell populations isolated on immunobeads contained two cell subsets: FOXP3+CD25+ Treg hydrolyzed exogenous ATP and suppressed CD4+ T cell proliferation, which was reversed by blocking ectonucleotidase activity. In contrast, the FOXP3negCD25neg T cells were CD127+CD49d+ and expressed IFNg, TNFa, and IL-10. The presence of two distinct CD4+CD39+ cell subsets in PBMC is a general phenomenon seen in normal donors, as well as patients with HIV and cancer. This suggests that phenotypic and functional plasticity characterizes the human Treg subset.
- Copyright © 2011 by The American Association of Immunologists, Inc.