Two distinct subsets of CD4+Foxp3+ regulatory T (Treg) cells have been described based on the differential expression of Helios, a transcription factor of the Ikaros family. Efforts to understand the origin and biological roles of these Treg populations in regulating immune responses have, however, been hindered by the lack of reliable surface markers to distinguish and isolate them for subsequent functional studies. Using a single-cell cloning strategy coupled with microarray analysis of different Treg functional subsets in humans, we identify the mRNA and protein expression of TIGIT and FCRL3 as a novel surface marker combination that distinguishes Helios+FOXP3+ from Helios−FOXP3+ memory cells. Unlike conventional markers that are modulated on conventional T cells upon activation, we show that the TIGIT/FCRL3 combination allows reliable identification of Helios+ Treg cells even in highly activated conditions in vitro as well as in PBMCs of autoimmune patients. We also demonstrate that the Helios−FOXP3+ Treg subpopulation harbors a larger proportion of nonsuppressive clones compared with the Helios+ FOXP3+ cell subset, which is highly enriched for suppressive clones. Moreover, we find that Helios− cells are exclusively responsible for the productions of the inflammatory cytokines IFN-γ, IL-2, and IL-17 in FOXP3+ cells ex vivo, highlighting important functional differences between Helios+ and Helios− Treg cells. Thus, we identify novel surface markers for the consistent identification and isolation of Helios+ and Helios− memory Treg cells in health and disease, and we further reveal functional differences between these two populations. These new markers should facilitate further elucidation of the functional roles of Helios-based Treg heterogeneity.

Immune dysregulation, polyendocrinopathy, enteropathy, X linked (IPEX) syndrome is a rare disorder in humans caused by germ-line mutations in the FOXP3 gene, a master transcriptional regulator for the development of CD4 regulatory T (Treg) cells. This T cell subset has global inhibitory functions that maintain immune homeostasis and mediate self-tolerance. Treg developmental deficiency or dysfunction is a hallmark of IPEX. It leads to severe, multi-organ, autoimmune phenomena including enteropathy, chronic dermatitis, endocrinopathy and other organ-specific diseases such as anaemia, thrombocytopenia, hepatitis and nephritis. In this review, the genetic, immunological and clinical characteristics of IPEX syndrome are described, and the impact of heritable mutations on the function of Treg cells highlighted.

Forkhead box protein 3 (Foxp3)(+) regulatory T (Treg) cells are critical mediators for the establishment of self-tolerance and immune homeostasis and for the control of pathology in various inflammatory responses. While Foxp3(+) Treg cells often control immune responses in secondary lymphoid tissues, they must also traffic to and persist within non-lymphoid tissues, where they integrate various environmental cues to coordinate and adapt their effector acitvities in these sites. In recent years, our group has made use of several mouse models, including the non-obese diabetic model of type 1 diabetes, to characterize the factors, which impact the homeostasis, function, and reprogramming potential of Foxp3(+) Treg cells in situ. In addition, our recent work shows that Foxp3(+) Treg cells possess distinct post-transcriptional mechanisms of gene regulation, namely mRNA translation, to modulate tissue-specific inflammatory responses. In humans, there is a pressing need for reliable markers of FOXP3(+) Treg cells and their related function in blood and tissue. Experimental progress in our group has enabled us to discover novel markers of FOXP3(+) Treg cell (dys)function and unique gene signatures that discriminate effector and Treg cells, as well as functional and dysfunctional FOXP3(+) Treg cells.

CD4FOXP3 regulatory T (T) cells are critical mediators of immune tolerance, and their deficiency owing to mutations in immunodysregulation polyendocrinopathy enteropathy X-linked syndrome (IPEX) patients results in severe autoimmunity. Different mutations result in a wide range of disease severity, reflecting the relative importance of the affected residues in the integrity of the FOXP3 protein and its various molecular interactions. We characterized the cellular and molecular impact of the most common IPEX mutation, p.A384T, on patient-derived T cells. We found that the p.A384T mutation abrogated the suppressive capacity of T cells while preserving FOXP3's ability to repress inflammatory cytokine production. This selective functional impairment is partly due to a specific disruption of FOXP3 binding to the histone acetyltransferase Tat-interacting protein 60 (TIP60) (KAT5) and can be corrected using allosteric modifiers that enhance FOXP3-TIP60 interaction. These findings reveal the functional impact of TIP60 in FOXP3-driven T biology and provide a potential target for therapeutic manipulation of T activity.

The CD4 + FOXP3 + regulatory T cell (Treg) subset is an indispensable mediator of immune tolerance. While high and stable expression of the transcription factor FOXP3 is considered a hallmark feature of Treg cells, our previous studies have demonstrated that the human FOXP3 + subset is functionally heterogeneous, whereby a sizeable proportion of FOXP3 + cells in healthy individuals have a diminished capacity to suppress the proliferation and cytokine production of responder cells. Notably, these non-suppressive cells are indistinguishable from suppressive Treg cells using conventional markers of human Treg. Here we investigate potential factors that underlie loss of suppressive function in human Treg cells. We show that high expression of the IL-6 family cytokine receptor subunit gp130 identifies Treg cells with reduced suppressive capacity ex vivo and in primary FOXP3 + clones. We further show that two gp130-signaling cytokines, IL-6 and IL-27, impair the suppressive capacity of human Treg cells. Finally, we show that gp130 signaling reduces the expression of the transcription factor Helios, whose expression is essential for stable Treg function. These results highlight the role of gp130 in regulating human Treg function, and suggest that modulation of gp130 signaling may serve as a potential avenue for the therapeutic manipulation of human Treg function.

Background: While a central role for the T helper (Th) 1/Th2 axis in food allergy has been established, the Th17 response in food-allergic humans has not been addressed. Methods: Th17 responses in 18 peanut-allergic children, who were also allergic to at least one additional food allergen, were assessed relative to 15 age-matched healthy controls. To account for the atopy background in the allergic children, 7 atopic, but not food-allergic, individuals and their age-matched controls were included in this study. PBMCs were analyzed by flow cytometry ex vivo or were stimulated in vitro with peanut allergens, gliadin, or tetanus toxoid followed by analysis of proliferation and cytokine production in antigen-responsive cells. Results: We observed a significantly lower interleukin (IL) 17 production in CD4+ T cells of food-allergic individuals ex vivo (p < 0.02). In vitro, we found that IL-17 production in CD4+ T cells in response to all antigens tested was significantly impaired in food-allergic subjects compared to healthy controls (Ara: p < 0.005; gliadin: p < 0.004; TT: p < 0.03). No significant differences were observed between atopic and nonatopic individuals with no food allergy. Conclusion: Our results thus reveal a systemic, non-allergen-specific defect in Th17 responses to antigen stimulation in food allergic individuals, suggesting a role for Th17 cells in the control of food allergy and implicating IL-17 as a potential biomarker for tolerance to food antigens.

An in-depth structural and functional analysis of the molecular domains of FOXP3 is essential for our understanding of the observed clinical heterogeneity and prognosis in IPEX.

Graft-versus-host disease is uncommon in autologous hematopoietic cell transplantation (HCT) and is typically brief and mild. We report unusual, protracted, and severe Omenn syndrome-like autoaggression following autologous HCT. We identified a profound FOXP3 ؉ regulatory T cell defect that coincided with hyperinflammatory T cell responses which were reversible with rapamycin in vitro. CASE REPORT