Regulatory T cells in health and disease

Abstract EN

CD4+ T cells are commonly divided into regulatory T (Treg) cells and conventional T helper (Th) cells.

Th cells control adaptive immunity against pathogens and cancer by activating other effector immune cells.

Treg cells are defined as CD4+ T cells in charge of suppressing potentially deleterious activities of Th cells.

Suggested functions for Treg cells include: prevention of autoimmune diseases by maintaining self-tolerance; suppression of allergy, asthma and pathogeninduced immunopathology; feto-maternal tolerance; and oral tolerance.

Identification of Treg cells remains problematic, because accumulating evidence suggests that all the presently-used Treg markers (CD25, CTLA-4, GITR, LAG-3, CD127 and Foxp3) represent general T-cell activation markers, rather than being truly Treg-specific.

Treg-cell activation is antigen-specific, which implies that suppressive activities of Treg cells are antigen-dependent.

The classification of Treg cells as a separate lineage remains controversial because the ability to suppress is not an exclusive Treg property.

Suppressive activities attributed to Treg cells may in reality, at least in some experimental settings, be exerted by conventional Th cell subsets, such as Th1, Th2, Th17 and T follicular (Tfh) cells.

Recent reports have also demonstrated that Foxp3+ Treg cells may differentiate in vivo into conventional effector Th cells, with or without concomitant down regulation of Foxp3