The many faces of regulatory T cells

"Regulatory T cell" is a generic name that globally covers a number of T cell subsets that can mediate suppression of cellular immunity in some in vitro and in vivo experiments. One of these subsets becomes differentiated in the thymus and is chiefly characterized by the expression of the Foxp3 transcription factor. It is postulated that these natural T reg cells recognize self peptides complexed to self MHC with moderate affinity and are thought to contribute to the preservation of self tolerance beyond negative thymic selection against high affinity anti-self T cell receptors. This is illustrated by mice and human patients devoid of these cells, who develop aggressive and extended autoimmune lymphoid infiltrates in different organs. CD4+ T cells producing anti-inflammatory cytokines also down regulate cellular immunity although they might cooperate with certain humoral responses. The rapidly progressing knowledge on the surface phenotype, and the transcriptome/proteome of these cells is offering plenty of opportunities for immune intervention. Deactivation or depletion of Treg cells might lead to increased immunity against viral chronicity or malignant diseases, whereas adoptive transfer or agonist stimulations of their function might have a role in the treatment of organ specific autoimmunity. However, abundant experimental discrepancies and uncertainties challenge and complicate this promising field for translational research.