Genomic definition of multiple ex vivo Treg sub-phenotypes

Regulatory T (Treg) cells that express the FoxP3 transcription factor are essential for lymphoid homeostasis and immune tolerance to self. Other non-immunological functions of Treg cells, such as controlling metabolic function in adipose tissue, are also emerging. Treg cells originate primarily in the thymus, but can also be elicited from conventional T cells by in vivo exposure to low-dose antigen or homeostatic expansion, or by activation in the presence of TGF in vitro. Treg cells are characterized by a distinct transcriptional signature controlled in part, but not solely, by FoxP3. For a better perspective on transcriptional control in Treg cells, we compared gene expression profiles of a broad panel of Treg cells from various origins or anatomical locations. Treg cells generated by different means form different sub-phenotypes identifiable by particular combinations of transcripts, none of which fully encompass the entire Treg signature. Molecules involved in Treg effector function, chemokine receptors, and the transcription factors that control them are differentially represented in these subphenotypes. Treg cells from the gut proved dissimilar to cells elicited by exposure to TGF, but instead they resembled a CD103+Klrg1+ subphenotype preferentially generated in response to lymphopenia.

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