Helios+ and Helios− Cells Coexist within the Natural FOXP3+ T Regulatory Cell Subset in Humans

Abstract

FOXP3-expressing T regulatory cells (Tregs) can be divided into two distinct subsets: naturally occurring Tregs (nTregs) that develop in the thymus, and induced Tregs (iTregs) that differentiate in peripheral tissues upon exposure to Ag in a tolerogenic environment. Recently it has been proposed that expression of Helios, an Ikaros family transcription factor, may specifically identify nTregs, allowing specific tracking of Tregs from different origins in health and disease. Surprisingly, we found that Helios- cells can be readily identified within naive (CD45RA+CD31+CCR7+CD62L+) FOXP3+ Tregs, a finding inconsistent with the notion that lack of Helios expression identifies Ag-experienced iTregs that should express memory markers. To investigate the phenotype and function of naive Helios+ and Helios− Tregs within the nTreg population, we isolated single-cell clones from each subset. We found that both Helios+ and Helios− nTreg clones have a similar suppressive capacity, as well as expression of FOXP3 and cell surface proteins, including CD39 and CTLA-4. Helios− nTregs, however, produced significantly more CCL3 and IFN-γ compared with Helios+ nTregs. Despite increased cytokine/chemokine production, Helios− FOXP3+ nTreg clones were demethylated at the FOXP3 Treg-specific demethylated region, indicative of Treg lineage stability. When cultured under Th1-polarizing conditions, Helios+ and Helios− nTreg clones had an equal ability to produce IFN-γ. Collectively, these data show that a lack of Helios expression does not exclusively identify human iTregs, and, to our knowledge, the data provide the first evidence for the coexistence of Helios+ and Helios− nTregs in human peripheral blood.

IL-1R1 is expressed on both Helios+ and Helios−FoxP3+CD4+ T cells in the rheumatic joint

“…Helios, a transcription factor belonging to the Ikaros family, has been studied extensively in the context of human T reg in health and disease [14,[16][17][18][19][20]36]. We have a longstanding interest in the rheumatic joint, a site of inflammation characterized by extensive cell influx and proliferation and where, in addition to activated memory effector T cells, T regs are also enriched significantly compared to PB [23].…”

“…Helios appears to be associated more with the path of activation rather than the origin of these cells [16,17]. However, it has been of interest to distinguish Helios 1 from Helios 2 T regs as some functional differences have been suggested, such as the ability to produce cytokines [18,19]. Recently, surface expression of IL-1R1 (IL-1 receptor type 1) in conjunction with CCR7 has been shown to be a useful combination of cell surface markers to distinguish Helios 2 T regs from Helios 1 T cells [20].…”

FOXP3+ regulatory T cells and their functional regulation

“…Helios and neuropilin-1 are usually highly expressed by tTreg cells but poorly expressed by pTreg cells; however, pTreg cells may upregulate expression of both these factors depending on local inflammatory conditions or the type of antigen-presenting cells and activation signals that are present. [11][12][13] Treg cells are a stable lineage with minimal capacity to dedifferentiate and convert into Teff cells, whereas CD25 low Treg cells may lose FOXP3 expression and convert into Th cells under certain conditions. 14 DNA methylation experiments have revealed that the Foxp3 promoter and conserved non-coding DNA sequence 2 (CNS2) region are highly demethylated in tTregs, which facilitate mRNA transcription of Foxp3 and contribute to lineage stability through FOXP3 expression, while in vitro induced Treg cells are substantially methylated at the CNS2 region.…”

Allogeneic Mature Human Dendritic Cells Generate Superior Alloreactive Regulatory T Cells in the Presence of IL-15

“…4A). nTregs before expansion consisted of ∼30% of HELIOS 2 T cells (51). Upon expansion this frequency did not change significantly.…”