CD73 Expression by CD4 T Cells Marks Early Effector Memory T Cells.

CD73 is a membrane bound ectoenzyme, dephosphorylating adenosine mono- and di-phosphate to immunosuppressive adenosine. It is strongly expressed by CD4CD25Foxp3 regulatory T cells, but when analysing conventional CD4 T cells only 50% express CD73. When analysing these two clearly distinct (i.e., CD73 and CD73) populations, we found that the naïve CD73CD4 subset exerted superior proliferation over the CD73CD4 cells, was more resistant to activation induced cells death (AICD) and was prone to develop into a "Th1-like" cell type, expressing the prototypic cytokines (IFN-γ, TNF-α) and specific transcription factors (i.e., Tbx21). Upon transfer into lymphopenic hosts, CD73CD4 cells exhibited increased proliferation and survival, and accumulated in inflammatory tissues, developing a CD44CD62L effector memory phenotype. Therefore, we conclude that CD73 in naïve CD4 T cells functions as a promotor of survival and proliferation of T cells, as well as a marker for their further differentiation into effector T cells.