Submitted July 2, 2008
Accepted November 6, 2008
IL-7 sustains CD31 expression in human naive CD4+ T cells and preferentially expands the CD31+ subset in a PI3K-dependent manner
Rita I Azevedo, Maria Vieira D Soares*, Joao T Barata, Rita Tendeiro, Ana Serra-Caetano, Rui M.M. Victorino, and Ana E. Sousa
Unidade de Imunologia Clinica, Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
Unidade de Biologia do Cancro, Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
Unidade de Citometria de Fluxo, Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
* Corresponding author; email: msoares{at}fm.ul.pt.
The CD31+ subset of human naive CD4+ T cells is thought to contain the population of cells that have recently emigrated from the thymus, whilst their CD31- counterparts have been proposed to originate from CD31+ after homeostatic cell division. Naïve T cell maintenance is known to involve homeostatic cytokines such as 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 as compared to 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 whilst preserving CD31. Furthermore, IL-7 sustained or increased CD31 expression even in non-proliferating cells. Both proliferation and CD31 maintenance were dependent on the activation of phosphoinositide 3-kinase (PI3K) signalling. 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.
