IL-2 Expression in Activated Human Memory FOXP3(+) Cells Critically Depends on the Cellular Levels of FOXP3 as Well as of Four Transcription Factors of  T Cell Activation.

The human CD4(+)FOXP3(+) T cell population is heterogeneous and consists of various subpopulations which remain poorly defined. Anergy and suppression are two main functional characteristics of FOXP3(+)Treg cells. We used the anergic behavior of FOXP3(+)Treg cells for a better discrimination and characterization of such subpopulations. We compared IL-2-expressing with IL-2-non-expressing cells within the memory FOXP3(+) T cell population. In contrast to IL-2-non-expressing FOXP3(+) cells, IL-2-expressing FOXP3(+) cells exhibit intermediate characteristics of Treg and Th cells concerning the Treg cell markers CD25, GITR, and Helios. Besides lower levels of FOXP3, they also have higher levels…