Expression of CD39 and CD73 ectonucleotidases in CD4+ lymphocyte populations in healthy children

Abstract

Purinergic system plays an important role in functional regulation of immune system. Extracellular ATP belongs to non-infectious danger signals (DAMP), has a pro-inflammatory effect and modulates the immune response. The end product of ATP breakdown, adenosine, plays an important role in limiting the inflammatory response. The activity of ectonucleotidase CD39 and CD73 supports the balance of ATP and adenosine at the site of inflammation. CD39 and CD73 expression is characterized by high variability. From the literature data, appropriate studies were carried out either in transgenic mice, or with adult healthy donors. The number of cells expressing CD39 and CD73 in T lymphocyte populations has not been evaluated in healthy children. Hence, our aim was to study the features of CD39 and CD73 expression in various subpopulations of CD4+ lymphocytes in apparently healthy children of different ages.
 We examined 45 healthy children aged 3.7 to 17.5 years (Me (Q0.25-Q0.75) 12.4 (10-16.1). The numbers of CD4+ cells, regulatory T lymphocytes (Treg CD4+CD25highCD127low), activated T helpers (Tact CD4+CD25+CD127high), and Th17 lymphocytes (CD4+CD161+CD3+) expressing CD39 and CD73 were evaluated by the flow cytometry.
 The number of cells expressing CD39 and CD73 depends on specific cell subpopulation. The highest content of CD39+ cells was observed in Tregs, and maximal amounts of CD73+ cells were found among Tact subset. In the Th17 lymphocyte subpopulation, there was no significant difference between the number of cells expressing CD39 and CD73. E have also shown an increase in the relative number of Th17 cells expressing CD73, along with age-dependent decrease in the relative number of Tact cells expressing CD39. An age-dependent decrease in absolute values with age was revealed for Treg, CD39+Treg, CD73+Treg, CD39+Th17, thus being consistent with age-related decrease in absolute numbers of lymphocytes and CD4+ cells.
 The obtained data concerning specific pattern of ectonucleotidases expression in functionally different populations of CD4+ lymphocytes should be taken into account when studying children with immune-mediated diseases from different age groups.