[CD4+CD25+ T regulatory cells: their physiology and role in modulating immune response]

Understanding the role of immune system homeostatic balance is crucial for a better understanding of the pathogenesis of many diseases. The efficient regulation of immune response has been recently investigated in numerous studies that emphasize the important role of CD4+CD25+ regulatory T cells. These regulatory cells suppress the proliferation and cytokine secretion of effector cells directly via cell-cell contact and probably indirectly via TGF-beta. This makes T regulatory cells responsible for the control and suppression of inappropriate immune response to self antigens. Moreover, CD4+CD25+ regulatory T cells have an important function in the immunopathology of cancer, allotransplantion, and allergy. Based on murine and human studies, this review presents a characterization of the origin, phenotype, and function of CD4+CD25+ regulatory T cells. In addition, we show a hypothetical mode of the in vivo action of regulatory T cells, which play a central role in maintaining immune homeostasis.