J Immunol 2010 Apr 1;184(7):3433-41. Epub 2010 Feb
Belkaid, Y; Korty, PE; Murray, PE; Shevach, EM.; Thornton, AM; Tran, DQ; Wohlfert, EA
Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
Helios, a member of the Ikaros transcription factor family, is preferentially expressed at the mRNA level by regulatory T cells (Treg cells). We evaluated Helios protein expression using a newly generated mAb and demonstrated that it is expressed in all thymocytes at the double negative 2 stage of thymic development. Although Helios was expressed by 100% of CD4(+)CD8(-)Foxp3(+) thymocytes, its expression in peripheral lymphoid tissues was restricted to a subpopulation ( approximately 70%) of Foxp3(+) T cells in mice and humans. Neither mouse nor human naive T cells induced to express Foxp3 in vitro by TCR stimulation in the presence of TGF-beta expressed Helios. Ag-specific Foxp3(+) T cells induced in vivo by Ag feeding also failed to express Helios. Collectively, these results demonstrate that Helios is potentially a specific marker of thymic-derived Treg cells and raises the possibility that a significant percentage of Foxp3(+) Treg cells are generated extrathymically.