Two Faces of Regulatory T Cells: From Immune Defense to Tumoral Progression

T cells are the most important cellular element of human immunity defending against virus, bacteria, non-self-tissue and tumor cells. Regulatory T cells (Tregs) are the major responsible for self-tolerance maintenance, especially those expressing forkhead box protein 3 (FOXP3) transcription factor. Tregs suppressive function is established through several mechanisms that are essential to immune system homeostasis, but also related to tumoral microenvironment. Recent studies have provided deeper understanding of Tregs role in cancer as well as promising therapeutic targets for improving prognosis in cancer patients. This review approaches Tregs subtypes, functions and its implication in tumor progression.