Helios expression defines a phenotypically distinct population of Treg cells

Abstract

Abstract The transcription factor Helios is expressed by 65–75% of Treg and we have proposed that it is a marker of thymic derived Treg (tTreg). In order to study the differences between Helios+ and Helios− Treg, we have generated a Helios-GFP/Foxp3-RFP double reporter mouse. Helios+ Treg expressed a more activated phenotype and had higher suppressive capability in vitro. Both subsets were equivalent in their ability to suppress IBD in vivo, but Helios+ Treg were more protective against disease induced by the transfer of splenocytes from scurfy mice. Both subsets expressed a highly demethylated Foxp3 TSDR, with slightly higher demethylation in the Helios+ Treg subset. Upon transfer to normal mice, both Helios+ and Helios− Treg cells maintained equal Foxp3 stability. However, upon transfer to lymphopenic mice, the percentage of cells from the Helios− subset that maintained Foxp3 expression was significantly lower than that of the Helios+ subset. Upon transfer to both normal and lymphopenic mice, Foxp3+Helios+ Treg maintained stable expression of Helios, while 30% of the Helios− Treg acquired low levels of Helios expression upon transfer to normal mice and 70–80% of the Helios− Treg acquired Helios expression when transferred to lymphopenic mice. Gene expression profiling of the two populations demonstrated 1000 differentially expressed genes. Additionally, TCR repertoire deep sequencing analysis revealed little to no overlap of the two populations. Taken together, our data indicate that Helios expression can differentiate two distinct populations of Treg with overlapping functions, most likely representing tTreg (Helios+) and stable peripherally-induced pTreg (Helios−). Supported by the Intramural Research Program of the NIH, NIAID.