Human CD4 super(+)CD39 super(+) regulatory T cells produce adenosine upon co-expression of surface CD73 or contact with CD73 super(+) exosomes or CD73 super(+) cells

• Published in: Clinical and experimental immunology 2014-08, Vol.177 (2), p.531-543
• Main Authors: Schuler, P J, Saze, Z, Hong, C-S, Muller, L, Gillespie, D G, Cheng, D, Harasymczuk, M, Mandapathil, M, Lang, S, Jackson, E K, Whiteside, T L
• Format: Article
• Language: English
• ISSN: 0009-9104; 1365-2249
• DOI: 10.1111/cei.12354

While murine CD4 super(+)CD39 super(+) regulatory T cells (T sub(reg)) co-express CD73 and hydrolyze exogenous (e) adenosine triphosphate (ATP) to immunosuppressive adenosine (ADO), surface co-expression of CD73 on human circulating CD4 super(+)CD39 super(+) T sub(reg) is rare. Therefore, the ability of human T sub(reg) to produce and utilize ADO for suppression remains unclear. Using mass spectrometry, we measured nucleoside production by subsets of human CD4 super(+)CD39 super(+) and CD4 super(+)CD39(-)CD73 super(+) T cells or CD19 super(+) B cells isolated from blood of 30 volunteers and 14 cancer patients. CD39 and CD73 expression was evaluated by flow cytometry, Western blots, confocal microscopy or reverse transcription-polymerase chain reaction (RT-PCR). Circulating CD4 super(+)CD39 super(+) T sub(reg) which hydrolyzed eATP to 5'-AMP contained few intracytoplasmic granules and had low CD73mRNA levels. Only 1% of these T sub(reg) were CD39 super(+)CD73 super(+). In contrast, CD4 super(+)CD39 super(neg)CD 73 super(+) T cells contained numerous CD73 super(+) granules in the cytoplasm and strongly expressed surface CD73. In vitro-generated T sub(reg) (Tr1) and most B cells were CD39 super(+)CD73 super(+). All these CD73 super(+) T cell subsets and B cells hydrolyzed 5'-AMP to ADO. Exosomes isolated from plasma of normal control (NC) or cancer patients carried enzymatically active CD39 and CD73 super(+) and, when supplied with eATP, hydrolyzed it to ADO. Only CD4 super(+)CD39 super(+) T sub(reg) co-incubated with CD4 super(+)CD73 super(+) T cells, B cells or CD39 super(+)CD73 super(+) exosomes produced ADO. Thus, contact with membrane-tethered CD73 was sufficient for ADO production by CD4 super(+)CD39 super(+) T sub(reg). In microenvironments containing CD4 super(+)CD73 super(+) T cells, B cells or CD39 super(+)CD73 super(+) exosomes, CD73 is readily available to CD4 super(+)CD39 super(+)CD73 super(neg) T sub(reg) for the production of immunosuppressive ADO.