IL-7 sustains CD31 expression in human naive CD4+ T cells and preferentially expands the CD31+ subset in a PI3K-dependent manner

Abstract

The CD31 + subset of human naive CD4+T cells is thought to contain the population of cells that have recently emigrated from the thymus, while their CD31 -counterparts have been proposed to originate from CD31+ cells after homeostatic cell division. Naive T-cell maintenance is known to involve homeostatic cytokines such as interleukin-7(IL-7). It remains to be investigated what role this cytokine has in the homeostasis of naive CD4+ T-cell subsets defined by CD31 expression. We provide evidence that IL-7 exerts a preferential proliferative effect on CD31 + naive CD4+ T cells from adult peripheral blood compared with the CD31 -subset. IL-7-driven proliferation did not result in loss of CD31 expression, suggesting that CD31 + naive CD4+ T cells can undergo cytokine-driven homeostatic proliferation while preserving CD31. Furthermore, IL-7 sustained or increased CD31 expression even in nonproliferating cells. Both proliferation and CD31 maintenance were dependent on the activation of phosphor-inositide 3-kinase(PI3K) signaling. Taken together, our data suggest that during adulthood CD31+ naive CD4 + T cells are maintained by IL-7 and that IL-7-based therapies may exert a preferential effect on this population. © 2009 by The American Society of Hematology.