Tumor-infiltrating regulatory T cells: origins and features.

Tumor cells evolve multiple sophisticated mechanisms to escape immune surveillance, one of which is to establish tolerogenic microenvironment by recruiting certain immune suppressive cells such as regulatory T cells (Tregs) and myeloid derived suppressor cells (MDSCs). Tregs are subpopulation of CD4⁺ T cells, which specialize in suppressing immune responses and preventing autoimmune damage to collateral tissue. Emerging evidence suggests that Treg cell number increases in various types of cancer, which correlates with tumor grade and poor patient prognosis. This review will focus on discussion of the origins and features of tumor-infiltrating Treg cells. Ultimately, these features may provide insight into potential therapeutic intervention by targeting Treg cells to invigorate immune response against tumor.