Phenotypic and Functional Properties of Helios+ Regulatory T Cells

Abstract

Helios, an Ikaros family transcription factor, is preferentially expressed at the mRNA and protein level in regulatory T cells. Helios expression previously appeared to be restricted to thymic-derived Treg. Consistent with recent data, we show here that Helios expression is inducible in vitro under certain conditions. To understand phenotypic and functional differences between Helios+ and Helios− Treg, we profiled cell-surface markers of FoxP3+ Treg using unmanipulated splenocytes. We found that CD103 and GITR are expressed at high levels on a subset of Helios+ Treg and that a Helios+ Treg population could be significantly enriched by FACS sorting using these two markers. Quantitative real-time PCR (qPCR) analysis revealed increased TGF-β message in Helios+ Treg, consistent with the possibility that this population possesses enhanced regulatory potential. In tumor-bearing mice, we found that Helios+ Treg were relatively over-represented in the tumor-mass, and BrdU studies showed that, in vivo, Helios+ Treg proliferated more than Helios− Treg. We hypothesized that Helios-enriched Treg might exert increased suppressive effects. Using in vitro suppression assays, we show that Treg function correlates with the absolute number of Helios+ cells in culture. Taken together, these data show that Helios+ Treg represent a functional subset with associated CD103 and GITR expression.

Helios expression in FoxP3+T regulatory cells

“…Most Tregs in human glioblastoma multiforme and mouse brain tumours expressed Helios [12]. Additionally, tumour-infiltrating FoxP3 + Tregs are largely positive for Helios expression [6,13]. Consistent with this, we also found that the majority (75 and 81%) of FoxP3 + Tregs isolated from two human metastatic lesions express Helios ( Figure 1A).…”

“…Since then, concerns have been raised on the suitability of Helios as thymic-derived nTreg marker. Some studies reported that Helios expression can be induced in vitro, depending on the method of activation rather than the origin of FoxP3 + cells [4][5][6]. Additionally, Helios was suggested as a marker of T cell activation and proliferation, rather than a marker for discriminating natural from induced Tregs [4].…”

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

“…Next we analysed the expression patterns of GITR, CTLA-4 and L-selectin lymph node homing receptor CD62L. All these three proteins have been associated with functional properties of T regs [32][33][34][35][36]. The frequencies of GITR-positive cells were equally high in both FoxP3 subsets in the inflamed joints and also overall higher compared to blood, where only a low frequency of GITR expression was observed (Fig.…”

“…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].…”

KLF2 is a rate-limiting transcription factor that can be targeted to enhance regulatory T-cell production

“…We next addressed the physiological relevance of KLF2 by examining peripheral Treg (pTreg) populations under homeostatic conditions. Reports indicate that Helios (an Ikaros transcription factor family member) and Neuropilin 1 (Nrp1, a membrane-bound surface receptor) are preferentially but not exclusively expressed by tTregs relative to pTregs (20)(21)(22)(23)(24)(25). To determine whether either of these molecules were appropriate surrogates for pTreg identification, we initially characterized expression patterns within the entire regulatory Tcell compartment.…”