IL-2 enhances gut homing potential of human naive regulatory t cells early in life

Recent evidence suggests early environmental factors are important for gut immune tolerance. Although the role of regulatory T (Treg) cells for gut immune homeostasis is well established, the development and tissue homing characteristics of Treg cells in children have not been studied in detail. In this article, we studied the development and homing characteristics of human peripheral blood Treg cell subsets and potential mechanisms inducing homing molecule expression in healthy children. We found contrasting patterns of circulating Treg cell gut and skin tropism, with abundant β7 integrin+ Treg cells at birth and increasing cutaneous lymphocyte Ag (CLA+) Treg cells later in life. β7 integrin+ Treg cells were predominantly naive, suggesting acquisition of Treg cell gut tropism early in development. In vitro, IL-7 enhanced gut homing but reduced skin homing molecule expression in conventional T cells, whereas IL-2 induced a similar effect only in Treg cells. This effect was more pronounced in cord compared with adult blood. Our results suggest that early in life, naive Treg cells may be driven for gut tropism by their increased sensitivity to IL-2-induced β7 integrin upregulation, implicating a potential role of IL-2 in gut immune tolerance during this critical period of development.