TH17 Cells in Autoimmunity and Immunodeficiency: Protective or Pathogenic?

In 2005 a newly discovered T helper cell subset that secreted interleukin (IL)-17 became the center of attention in immunology. Initial studies painted Th17 cells as the culprit for destruction in many different autoimmune and auto-inflammatory diseases. Subsequently, the discovery of patients with primary immunodeficiencies in the IL-17 pathway taught us that Th17 cells have a critical role in defense against certain fungal and bacterial infections. Moreover, the paradoxical exacerbation of Crohn’s disease in the clinical trials of a Secukinumab (AIN457), a fully human neutralizing antibody to IL-17A, has cast into doubt a universal pro-inflammatory and harmful role for Th17 cells. Evidence now suggests that depending on the environment Th17 cells can alter their differentiation program, ultimately giving rise to either protective or pro-inflammatory cells. In this review we will summarize the evidence from patients with immunodeficiencies, autoimmune, or auto-inflammatory diseases that teaches us how the pro-inflammatory versus protective function of Th17 cells varies within the context of different human diseases

The parasite cytokine mimic <i>Hp</i>-TGM potently replicates the regulatory effects of TGF-β on murine CD4+ T cells

Transforming growth factor‐beta (TGF‐β) family proteins mediate many vital biological functions in growth, development and regulation of the immune system. TGF‐β itself controls immune homeostasis and inflammation, including conversion of naïve CD4+ T cells into Foxp3+ regulatory T cells (Tregs) in the presence of IL‐2 and T cell receptor ligands. The helminth parasite Heligmosomoides polygyrus exploits this pathway through a structurally novel TGF‐β mimic (Hp‐TGM), which binds to mammalian TGF‐β receptors and induces Tregs. Here, we performed detailed comparisons of Hp‐TGM with mammalian TGF‐β. Compared to TGF‐β, Hp‐TGM induced greater numbers of Foxp3+ Tregs (iTregs), with more intense Foxp3 expression. Both ligands upregulated Treg functional markers CD73, CD103 and PD‐L1, but Hp‐TGM induced significantly higher CD39 expression than did TGF‐β. Interestingly, in contrast to canonical TGF‐β signalling through Smad2/3, Hp‐TGM stimulation was slower and more sustained. Gene expression profiles induced by TGF‐β and Hp‐TGM were remarkably similar, and both types of iTregs suppressed T cell responses in vitro and EAE‐driven inflammation in vivo. In vitro, both types of iTregs were equally stable under inflammatory conditions, but Hp‐TGM‐induced iTregs were more stable in vivo during DSS‐induced colitis, with greater retention of Foxp3 expression and lower conversion to a ROR‐γt+ phenotype. Altogether, results from this study suggest that the parasite cytokine mimic, Hp‐TGM, may deliver a qualitatively different signal to CD4+ T cells with downstream consequences for the long‐term stability of iTregs. These data highlight the potential of Hp‐TGM as a new modulator of T cell responses in vitro and in vivo

Human CD25+CD4+ T Suppressor Cell Clones Produce Transforming Growth Factor β, but not Interleukin 10, and Are Distinct from Type 1 T Regulatory Cells

T regulatory (Tr) cells are essential for the induction of peripheral tolerance. Several types of Tr cells exist, including CD4+ T cells which express CD25 constitutively and suppress immune responses via direct cell-to-cell interactions, and type 1 T regulatory (Tr1) cells, which function via secretion of interleukin (IL)-10 and transforming growth factor (TGF)-β. The relationship between CD25+CD4+ T cells and Tr1 cells remains unclear. Here, we demonstrate at the clonal level that Tr1 and CD25+CD4+ T cells are two distinct subsets of regulatory cells with different cytokine production profiles. Furthermore, CD25−CD4+ T cells can be rendered anergic by IL-10 and differentiated into Tr1 cells in the absence of CD25+CD4+ T cells. Cloned human CD25+CD4+ T cell populations are heterogeneous and only a subset of clones continues to express high levels of CD25 and is suppressive. The intensity of CD25, cytotoxic T lymphocyte antigen (CTLA)-4, and glucocorticoid-induced tumor necrosis factor (TNF) receptor expression correlates with the suppressive capacity of the T cell clones. None of the CD25+CD4+ T cell clones with suppressive function produce IL-10, but all produce TGF-β. Suppression mediated by CD25+CD4+ T cell clones is partially dependent on TGF-β, but not on constitutive high expression of CD25. Together these data indicate that naturally occurring human CD25+CD4+ T cells are distinct from IL-10–producing Tr1 cells

Generation of Potent and Stable Human CD4+ T Regulatory Cells by Activation-independent Expression of FOXP3

Therapies based on enhancing the numbers and/or function of T regulatory cells (Tregs) represent one of the most promising approaches to restoring tolerance in many immune-mediated diseases. Several groups have investigated whether human Tregs suitable for cellular therapy can be obtained by in vitro expansion, in vitro conversion of conventional T cells into Tregs, or gene transfer of the FOXP3 transcription factor. To date, however, none of these approaches has resulted in a homogeneous and stable population of cells that is as potently suppressive as ex vivo Tregs. We developed a lentivirus-based strategy to ectopically express high levels of FOXP3 that do not fluctuate with the state of T-cell activation. This method consistently results in the development of suppressive cells that are as potent as Tregs and can be propagated as a homogeneous population. Moreover, using this system, both naive and memory CD4+ T cells can be efficiently converted into Tregs. To date, this is the most efficient and reliable protocol for generating large numbers of suppressive CD4+ Tregs, which can be used for further biological study and developed for antigen-specific cellular therapy applications

Process analytical utility of Raman spectroscopy for cell therapy manufacturing

Please click Additional Files below to see the full abstract

Induction of stable human FOXP3⁺ Tregs by a parasite-derived TGF-β mimic

Immune homeostasis in the intestine is tightly controlled by FOXP3 + regulatory T cells (Tregs), defects of which are linked to the development of chronic conditions, such as inflammatory bowel disease (IBD). As a mechanism of immune evasion, several species of intestinal parasites boost Treg activity. The parasite Heligmosomoides polygyrus is known to secrete a molecule (Hp-TGM) that mimics the ability of TGF-β to induce FOXP3 expression in CD4 + T cells. The study aimed to investigate whether Hp-TGM could induce human FOXP3 + Tregs as a potential therapeutic approach for inflammatory diseases. CD4 + T cells from healthy volunteers were expanded in the presence of Hp-TGM or TGF-β. Treg induction was measured by flow cytometric detection of FOXP3 and other Treg markers, such as CD25 and CTLA-4. Epigenetic changes were detected using ChIP-Seq and pyrosequencing of FOXP3. Treg phenotype stability was assessed following inflammatory cytokine challenge and Treg function was evaluated by cellular co-culture suppression assays and cytometric bead arrays for secreted cytokines. Hp-TGM efficiently induced FOXP3 expression (&gt; 60%), in addition to CD25 and CTLA-4, and caused epigenetic modification of the FOXP3 locus to a greater extent than TGF-β. Hp-TGM-induced Tregs had superior suppressive function compared with TGF-β-induced Tregs, and retained their phenotype following exposure to inflammatory cytokines. Furthermore, Hp-TGM induced a Treg-like phenotype in in vivo differentiated Th1 and Th17 cells, indicating its potential to re-program memory cells to enhance immune tolerance. These data indicate Hp-TGM has potential to be used to generate stable human FOXP3 + Tregs to treat IBD and other inflammatory diseases. </p

Circulating gluten-specific FOXP3 + CD39 + regulatory T cells have impaired suppressive function in patients with celiac disease

Background Celiac disease is a chronic immune-mediated inflammatory disorder of the gut triggered by dietary gluten. Although the effector T-cell response in patients with celiac disease has been well characterized, the role of regulatory T (Treg) cells in the loss of tolerance to gluten remains poorly understood. Objective We sought to define whether patients with celiac disease have a dysfunction or lack of gluten-specific forkhead box protein 3 (FOXP3)+ Treg cells. Methods Treated patients with celiac disease underwent oral wheat challenge to stimulate recirculation of gluten-specific T cells. Peripheral blood was collected before and after challenge. To comprehensively measure the gluten-specific CD4+ T-cell response, we paired traditional IFN-γ ELISpot with an assay to detect antigen-specific CD4+ T cells that does not rely on tetramers, antigen-stimulated cytokine production, or proliferation but rather on antigen-induced coexpression of CD25 and OX40 (CD134). Results Numbers of circulating gluten-specific Treg cells and effector T cells both increased significantly after oral wheat challenge, peaking at day 6. Surprisingly, we found that approximately 80% of the ex vivo circulating gluten-specific CD4+ T cells were FOXP3+CD39+ Treg cells, which reside within the pool of memory CD4+CD25+CD127lowCD45RO+ Treg cells. Although we observed normal suppressive function in peripheral polyclonal Treg cells from patients with celiac disease, after a short in vitro expansion, the gluten-specific FOXP3+CD39+ Treg cells exhibited significantly reduced suppressive function compared with polyclonal Treg cells. Conclusion This study provides the first estimation of FOXP3+CD39+ Treg cell frequency within circulating gluten-specific CD4+ T cells after oral gluten challenge of patients with celiac disease. FOXP3+CD39+ Treg cells comprised a major proportion of all circulating gluten-specific CD4+ T cells but had impaired suppressive function, indicating that Treg cell dysfunction might be a key contributor to disease pathogenesis

SHIP-Deficient Dendritic Cells, Unlike Wild Type Dendritic Cells, Suppress T Cell Proliferation via a Nitric Oxide-Independent Mechanism

Dendritic cells (DCs) not only play a crucial role in activating immune cells but also suppressing them. We recently investigated SHIP's role in murine DCs in terms of immune cell activation and found that TLR agonist-stimulated SHIP-/- GM-CSF-derived DCs (GM-DCs) were far less capable than wild type (WT, SHIP+/+) GM-DCs at activating T cell proliferation. This was most likely because SHIP-/- GM-DCs could not up-regulate MHCII and/or co-stimulatory receptors following TLR stimulation. However, the role of SHIP in DC-induced T cell suppression was not investigated.In this study we examined SHIP's role in DC-induced T cell suppression by co-culturing WT and SHIP-/- murine DCs, derived under different conditions or isolated from spleens, with αCD3+ αCD28 activated WT T cells and determined the relative suppressive abilities of the different DC subsets. We found that, in contrast to SHIP+/+ and -/- splenic or Flt3L-derived DCs, which do not suppress T cell proliferation in vitro, both SHIP+/+ and -/- GM-DCs were capable of potently suppressing T cell proliferation. However, WT GM-DC suppression appeared to be mediated, at least in part, by nitric oxide (NO) production while SHIP-/- GM-DCs expressed high levels of arginase 1 and did not produce NO. Following exhaustive studies to ascertain the mechanism of SHIP-/- DC-mediated suppression, we could conclude that cell-cell contact was required and the mechanism may be related to their relative immaturity, compared to SHIP+/+ GM-DCs.These findings suggest that although both SHIP+/+ and -/- GM-DCs suppress T cell proliferation, the mechanism(s) employed are different. WT GM-DCs suppress, at least in part, via IFNγ-induced NO production while SHIP-/- GM-DCs do not produce NO and suppression can only be alleviated when contact is prevented

Inflammation-Driven Reprogramming of CD4+Foxp3+ Regulatory T Cells into Pathogenic Th1/Th17 T Effectors Is Abrogated by mTOR Inhibition in vivo

While natural CD4+Foxp3+ regulatory T (nTREG) cells have long been viewed as a stable and distinct lineage that is committed to suppressive functions in vivo, recent evidence supporting this notion remains highly controversial. We sought to determine whether Foxp3 expression and the nTREG cell phenotype are stable in vivo and modulated by the inflammatory microenvironment. Here, we show that Foxp3+ nTREG cells from thymic or peripheral lymphoid organs reveal extensive functional plasticity in vivo. We show that nTREG cells readily lose Foxp3 expression, destabilizing their phenotype, in turn, enabling them to reprogram into Th1 and Th17 effector cells. nTREG cell reprogramming is a characteristic of the entire Foxp3+ nTREG population and the stable Foxp3NEG TREG cell phenotype is associated with a methylated foxp3 promoter. The extent of nTREG cell reprogramming is modulated by the presence of effector T cell-mediated signals, and occurs independently of variation in IL-2 production in vivo. Moreover, the gut microenvironment or parasitic infection favours the reprogramming of Foxp3+ TREG cells into effector T cells and promotes host immunity. IL-17 is predominantly produced by reprogrammed Foxp3+ nTREG cells, and precedes Foxp3 down-regulation, a process accentuated in mesenteric sites. Lastly, mTOR inhibition with the immunosuppressive drug, rapamycin, stabilizes Foxp3 expression in TREG cells and strongly inhibits IL-17 but not RORγt expression in reprogrammed Foxp3− TREG cells. Overall, inflammatory signals modulate mTOR signalling and influence the stability of the Foxp3+ nTREG cell phenotype