Differential regulatory capacity of CD25+ T regulatory cells and preactivated CD25+ T regulatory cells on development, functional activation, and proliferation of Th2 cells

CD25(+) T regulatory (Treg) cells play a central role regarding the maintenance of peripheral tolerance via suppression of autoaggressive CD4(+) T cells, CD8(+) T cells, and Th1 cells. In this study we demonstrate that CD25(+) Treg cells can also suppress the differentiation of murine conventional CD4(+) T cells toward Th2 cells in a contact-dependent manner. However, the cytokine production and proliferation of established Th2 cells could not be inhibited by freshly isolated CD25(+) Treg cells, whereas a strong inhibition of differentiated Th2 cells by in vitro preactivated CD25(+) Treg cells could be observed. Inhibition of both conventional CD4(+) T cells and Th2 cells is accompanied by a strong enhancement of the expression of FoxP3 in the suppressed T cells. Hence, our study indicates that CD25(+) Treg cells have a therapeutic potential for Th2-mediated diseases and suggests a novel mechanism of suppression mediated by the transcriptional repressor FoxP3.