In vitro expanded human CD4+CD25+ regulatory T cells suppress effector T cell proliferation

Umbilical cord blood and peripheral blood-derived regulatory T cells therapy: Progress in type 1 diabetes

Regulatory T cells (Tregs) are key regulators for the inflammatory response and play a role in maintaining the immune tolerance. Type 1 diabetes (T1D) is a relatively common autoimmune disease that results from the loss of immune tolerance to β-cell-associated antigens. Preclinical models have demonstrated the safety and efficacy of Tregs given in transplant rejection and autoimmune diseases such as T1D. Adoptive transfer of Tregs has been utilized in clinical trials for over a decade. However, the achievement of the adoptive transfer of Tregs therapy in clinical application remains challenging. In this review, we highlight the characterization of Tregs and compare the differences between umbilical cord blood and adult peripheral blood-derived Tregs. Additionally, we summarize conditional modifications in the expansion of Tregs in clinical trials, especially for the treatment of T1D. Finally, we discuss the existing technical challenges for Tregs in clinical trials for the treatment of T1D.

Regulatory T Cell Therapeutics for Neuroinflammatory Disorders

A delicate balance of immune regulation exists in the central nervous system (CNS) that is often dysreg-ulated in neurological diseases, making them complicated to treat. With altered immune surveillance in the diseased or injured CNS, signals that are beneficial in the homeostatic CNS can be disrupted and lead to neuroinflammation. Recent advances in niche immune cell subsets have provided insight into the complicated cross-talk between the nervous system and the immune system. Regulatory T cells (Tregs) are a subset of T cells that are capable of suppressing effector T-cell activation and regulating immune tolerance, and play an important role in neuroprotection. Tregs have been shown to be effective therapies in a variety of immune-related disorders including, graft-versus-host disease (GVHD), type 1 diabetes (T1D), and inflammatory bowel disease (IBD), as well as within the CNS. Recently, significant advancements in engineering T cells, such as chimeric antigen receptor (CAR) T cells, have led to several approved therapies suggesting the safety and efficacy for similar engineered Treg therapies. Further, as understanding of the immune system's role in neuroinflammation has progressed, Tregs have recently become a potential therapeutic in the neurology space. In this review, we discuss Tregs and their evolving role as therapies for neuroinflammatory related disorders.

Autologous culture model of nodal B-cell lymphoma identifies ex vivo determinants of response to bispecific antibodies

High Helios but low ICOS expression in lymph node–derived regulatory T cells associates with ex vivo failure of BsAbs.

Lenalidomide, nivolumab, and atezolizumab improve ex vivo response to BsAbs by potentiating T-cell effector functions.

Bispecific antibodies (BsAbs) can induce long-term responses in patients with refractory and relapsed B-cell lymphoma. Nevertheless, response rates across patients are heterogeneous, and the factors determining quality and duration of responses are poorly understood. To identify key determinants of response to BsAbs, we established a primary, autologous culture model allowing us to mimic treatment with CD3xCD19 and CD3xCD20 BsAbs within the lymph node microenvironment ex vivo. T cell–mediated killing of lymphoma cells and proliferation of T cells varied significantly among patients but highly correlated between BsAbs targeting CD20 or CD19. Ex vivo response to BsAbs was significantly associated with expansion of T cells and secretion of effector molecules (eg, granzyme B, perforin) but not with expression of T-cell exhaustion (eg, PD1, TIM3) or activation markers (eg, CD25, CD69) or formation of intercellular contacts. In addition, we identified a distinct phenotype of regulatory T cells that was linked to ex vivo response independently from T-cell frequency at baseline. High expression levels of Aiolos (IKZF1), ICOS, and CXCR5 were positively associated with ex vivo response, whereas strong expression of Helios (IKZF2) had an unfavorable impact on ex vivo response to BsAbs. We further showed that lenalidomide, nivolumab, and atezolizumab improved ex vivo response to BsAbs by potentiating T-cell effector functions. In summary, our ex vivo study identified a distinct regulatory T-cell phenotype as a potential contributor to treatment failure of BsAbs and suggests drug combinations of high clinical relevance that could improve the efficacy of BsAbs.

NFκB-Activated COX2/PGE2/EP4 Axis Controls the Magnitude and Selectivity of BCG-Induced Inflammation in Human Bladder Cancer Tissues

Simple Summary

The clinical effectiveness of Bacillus Calmette-Guérin (BCG) is limited to patients with early stages of bladder cancer (BlCa) and its effects are often transient. To understand the mechanisms limiting the effectiveness of BCG, we evaluated its impact on the human BlCa tumor microenvironment (TME) and the feasibility of its pharmacologic modulation. We observed that BCG non-selectively induces both CTL-attracting chemokines and Treg/MDSC attractants and suppressive factors in human BlCa tissue explants, in a mechanism involving NFκB-induced PGE₂ synthesis and EP4 signaling. In contrast to non-selective impact of NFκB blockade on BCG-induced inflammation, the PGE₂ antagonism selectively enhanced the BCG-driven production of CTL attractants but eliminated the induction of Treg/MDSC attractants and suppressive factors, enhancing the CTL migration but reducing Treg attraction to BCG-treated BlCa. Since intratumoral CTL accumulation predicts long term patient outcomes and the effectiveness of cancer immunotherapies, our data indicates the feasibility of targeting the PGE₂-chemokine interplay to enhance the therapeutic effects of BCG.

Abstract

Bacillus Calmette-Guérin (BCG) is commonly used in the immunotherapy of bladder cancer (BlCa) but its effectiveness is limited to only a fraction of patients. To identify the factors that regulate the response of human BlCa tumor microenvironment (TME) to BCG, we used the ex vivo whole-tissue explant model. The levels of COX2 in the BCG-activated explants closely correlated with the local production of Treg- and MDSCS attractants and suppressive factors, while the baseline COX2 levels did not have predictive value. Accordingly, we observed that BCG induced high levels of MDSC- and Treg-attracting chemokines (CCL22, CXCL8, CXCL12) and suppressive factors (IDO1, IL-10, NOS2). These undesirable effects were associated with the nuclear translocation of phosphorylated NFκB, induction of COX2, the key enzyme controlling PGE₂ synthesis, and elevation of a PGE₂ receptor, EP4. While NFκB blockade suppressed both the desirable and undesirable components of BCG-driven inflammation, the inhibitors of PGE₂ synthesis (Celecoxib or Indomethacin) or signaling (EP4-selective blocker, ARY-007), selectively eliminated the induction of MDSC/Treg attractants and immunosuppressive factors but enhanced the production of CTL attractants, CCL5, CXCL9 and CXCL10. PGE₂ blockade allowed for the selectively enhanced migration of CTLs to the BCG-treated BlCa samples and eliminated the enhanced migration of Tregs. Since the balance between the CTLs and suppressive cells in the TME predicts the outcomes in patients with BlCa and other diseases, our data help to elucidate the mechanisms which limit the effectiveness of BCG therapies and identify new targets to enhance their therapeutic effects.

Adoptive transfer of Tregs: A novel strategy for cell-based immunotherapy in spontaneous abortion: Lessons from experimental models

Since half of the genes are inherited from the paternal side, the maternal immune system has to tolerate the presence of foreign paternal antigens. Regulatory T cells facilitate the development and maintenance of peripheral tissue tolerance of the fetus during pregnancy. Reduction in regulatory T cells is associated with complications of pregnancy, including spontaneous abortion. Recent studies in mouse models have shown that the adoptive transfer of Tregs can prevent spontaneous abortion in mouse models through improving maternal tolerance. Thus, adoptive cell therapy using autologous Tregs could potentially be a novel therapeutic approach for cell-based immunotherapy in women with unexplained spontaneous abortion. Besides, strategies for activating and expanding antigen-specific Tregs ex vivo and in vivo based on pharmacological agents can pave the foundation for an approach incorporating immunotherapy and pharmacotherapy. This review aims to elaborate on the current understanding of the therapeutic potential of the adoptive transfer of Tregs in the treatment of spontaneous abortion disease.

Immunomodulation Followed by Antigen-Specific Treg Infusion Controls Islet Autoimmunity

Optimal immune-based therapies for type 1 diabetes (T1D) should restore self-tolerance without inducing chronic immunosuppression. CD4⁺Foxp3⁺ regulatory T cells (T_regs) are a key cell population capable of facilitating durable immune tolerance. However, clinical trials with expanded T_regs in T1D and solid-organ transplant recipients are limited by poor T_reg engraftment without host manipulation. We showed that T_reg engraftment and therapeutic benefit in nonautoimmune models required ablative host conditioning. Here, we evaluated T_reg engraftment and therapeutic efficacy in the nonobese diabetic (NOD) mouse model of autoimmune diabetes using nonablative, combinatorial regimens involving the anti-CD3 (αCD3), cyclophosphamide (CyP), and IAC (IL-2/JES6-1) antibody complex. We demonstrate that αCD3 alone induced substantial T-cell depletion, impacting both conventional T cells (T_conv) and T_regs, subsequently followed by more rapid rebound of T_regs Despite robust depletion of host T_conv and host T_regs, donor T_regs failed to engraft even with interleukin-2 (IL-2) support. A single dose of CyP after αCD3 depleted rebounding host T_regs and resulted in a 43-fold increase in donor T_reg engraftment, yet polyclonal donor T_regs failed to reverse diabetes. However, infusion of autoantigen-specific T_regs after αCD3 alone resulted in robust T_reg engraftment within the islets and induced remission in all mice. This novel combinatorial therapy promotes engraftment of autoantigen-specific donor T_regs and controls islet autoimmunity without long-term immunosuppression.

OX40L-JAG1-Induced Expansion of Lineage-Stable Regulatory T Cells Involves Noncanonical NF-κB Signaling

Foxp3⁺T regulatory cells (Tregs) control autoimmune response by suppressing proliferation and effector functions of self-reactive Foxp3^-CD4⁺/CD8⁺ T cells and thereby maintain the critical balance between self-tolerance and autoimmunity. Earlier, we had shown that OX40L-JAG1 cosignaling mediated through their cognate receptors OX40 and Notch3 preferentially expressed on murine Tregs can selectively induce their proliferation in the absence of TCR stimulation. However, the differential molecular mechanisms regulating TCR-independent versus TCR-dependent Treg proliferation and lineage stability of the expanded Tregs remained unknown. In this study, we show that OX40L-JAG1 treatment induced TCR-independent proliferation of Tregs in the thymus and periphery. The use of Src kinase inhibitor permitted us to demonstrate selective inhibition of TCR-dependent T cell proliferation with little to no effect on OX40L-JAG1-induced TCR-independent Treg expansion in vitro, which was critically dependent on noncanonical NF-κB signaling. OX40L-JAG1-expanded Tregs showed sustained lineage stability as indicated by stable demethylation marks in Treg signature genes such as Foxp3, Il2ra, Ctla4, Ikzf2, and Ikzf4. Furthermore, OX40L-JAG1 treatment significantly increased CTLA4⁺ and TIGIT⁺ Tregs and alleviated experimental autoimmune thyroiditis in mice. Relevance of our findings to humans became apparent when human OX40L and JAG1 induced TCR-independent selective expansion of human Tregs in thymocyte cultures and increased human Tregs in the liver tissue of humanized NSG mice. Our findings suggest that OX40L-JAG1-induced TCR-independent Treg proliferation is a conserved mechanism that can be used to expand lineage-stable Tregs to treat autoimmune diseases.

TGF-β-responsive CAR-T cells promote anti-tumor immune function

A chimeric antigen receptor (CAR) that responds to transforming growth factor beta (TGF‐β) enables the engineering of T cells that convert this immunosuppressive cytokine into a potent T‐cell stimulant. However, clinical translation of TGF‐β CAR‐T cells for cancer therapy requires the ability to productively combine TGF‐β responsiveness with tumor‐targeting specificity. Furthermore, the potential concern that contaminating, TGF‐β?producing regulatory T (Treg) cells may preferentially expand during TGF‐β CAR‐T cell manufacturing and suppress effector T (Teff) cells demands careful evaluation. Here, we demonstrate that TGF‐β CAR‐T cells significantly improve the anti‐tumor efficacy of neighboring cytotoxic T cells. Furthermore, the introduction of TGF‐β CARs into mixed T‐cell populations does not result in the preferential expansion of Treg cells, nor do TGF‐β CAR‐Treg cells cause CAR‐mediated suppression of Teff cells. These results support the utility of incorporating TGF‐β CARs in the development of adoptive T‐cell therapy for cancer.

Cytokines affecting CD4+T regulatory cells in transplant tolerance. III. Interleukin-5 (IL-5) promotes survival of alloantigen-specific CD4+ T regulatory cells

CD4⁺T cells mediate antigen-specific allograft tolerance, but die in culture without activated lymphocyte derived cytokines. Supplementation of the media with cytokine rich supernatant, from ConA activated spleen cells, preserves the capacity of tolerant cells to transfer tolerance and suppress rejection. rIL-2 or rIL-4 alone are insufficient to maintain these cells, however. We observed that activation of naïve CD4⁺CD25⁺FOXP3⁺Treg with alloantigen and the Th2 cytokine rIL-4 induces them to express interleukin-5 specific receptor alpha (IL-5Rα) suggesting that IL-5, a Th2 cytokine that is produced later in the immune response may promote tolerance mediating Treg. This study examined if recombinant IL-5(rIL-5) promoted survival of tolerant CD4⁺, especially CD4⁺CD25⁺T cells. CD4⁺T cells, from DA rats tolerant to fully allogeneic PVG heart allografts surviving over 100days without on-going immunosuppression, were cultured with PVG alloantigen and rIL-5. The ability of these cells to adoptively transfer tolerance to specific-donor allograft and suppress normal CD4⁺T cell mediated rejection in adoptive DA hosts was examined. Tolerant CD4⁺CD25⁺T cells' response to rIL-5 and expression of IL-5Rα was also assessed. rIL-5 was sufficient to promote transplant tolerance mediating CD4⁺T cells' survival in culture with specific-donor alloantigen. Tolerant CD4⁺T cells cultured with rIL-5 retained the capacity to transfer alloantigen-specific tolerance and inhibited naïve CD4⁺T cells' capacity to effect specific-donor graft rejection. rIL-5 promoted tolerant CD4⁺CD25⁺T cells' proliferation in vitro when stimulated with specific-donor but not third-party stimulator cells. Tolerant CD4⁺CD25⁺T cells expressed IL-5Rα. This study demonstrated that IL-5 promoted the survival of alloantigen-specific CD4⁺CD25⁺T cells that mediate transplant tolerance.

Cell Therapy in Kidney Transplantation: Focus on Regulatory T Cells

Renal transplantation is the renal replacement modality of choice for suitable candidates with advanced CKD or ESRD. Prevention of rejection, however, requires treatment with nonspecific pharmacologic immunosuppressants that carry both systemic and nephrologic toxicities. Use of a patient's own suppressive regulatory T cells (Tregs) is an attractive biologic approach to reduce this burden. Here, we review the immunologic underpinnings of Treg therapy and technical challenges to developing successful cell therapy. These issues include the selection of appropriate Treg subsets, ex vivo Treg expansion approaches, how many Tregs to administer and when, and how to care for patients after Treg administration.

Soluble OX40L and JAG1 Induce Selective Proliferation of Functional Regulatory T-Cells Independent of canonical TCR signaling

Regulatory T-cells (Tregs) play a pivotal role in maintaining peripheral tolerance. Increasing Treg numbers/functions has been shown to ameliorate autoimmune diseases. However, common Treg expansion approaches use T-Cell Receptor (TCR)-mediated stimulation which also causes proliferation of effector T-cells (Teff). To overcome this limitation, purified patient-specific Tregs are expanded ex vivo and transfused. Although promising, this approach is not suitable for routine clinical use. Therefore, an alternative approach to selectively expand functional Tregs in vivo is highly desired. We report a novel TCR-independent strategy for the selective proliferation of Foxp3+Tregs (without Teff proliferation), by co-culturing CD4+ T-cells with OX40 L+Jagged(JAG)-1+ bone marrow-derived DCs differentiated with GM-CSF or treating them with soluble OX40 L and JAG1 in the presence of exogenous IL-2. Tregs expanded using soluble OX40 L and JAG1 were of suppressive phenotype and delayed the onset of diabetes in NOD mice. Ligation of OX40 L and JAG1 with their cognate-receptors OX40 and Notch3, preferentially expressed on Tregs but not on Teff cells, was required for selective Treg proliferation. Soluble OX40L-JAG1-induced NF-κB activation as well as IL-2-induced STAT5 activation were essential for the proliferation of Tregs with sustained Foxp3 expression. Altogether, these findings demonstrate the utility of soluble OX40 L and JAG1 to induce TCR-independent Treg proliferation.

Natural regulatory T cells from patients with end-stage renal disease can be used for large-scale generation of highly suppressive alloantigen-specific Tregs

Natural occurring regulatory T cells (nTregs) have the potential to offer a targeted approach of immunosuppression and are the cell type of interest for inducing tolerance in kidney transplantation. End-stage renal disease (ESRD) profoundly affects the composition and function of circulating T cells but little is known with respect to how nTreg potential is affected. To address this, nTregs of patients with ESRD (on dialysis or not) and healthy individuals were isolated, expanded using allogeneic mature monocyte-derived dendritic cells followed by anti-CD3/anti-CD28-coated beads and the different nTregs were extensively characterized by the demethylation status of the Treg-specific demethylated region within FOXP3 and expression of typical nTreg markers. Additionally, the suppressive capacity as well as cytokine producing cells were analyzed for allogeneic mature monocyte-derived dendritic cell-expanded nTregs. Compared to age- and gender-matched healthy individuals, similar frequencies of nTregs were present within the circulation of patients with ESRD either on dialysis or not. The isolated nTregs could be equally well or even better expanded using allogeneic mature monocyte-derived dendritic cells and extensive characterization did not reveal significant differences. The demethylation status of the Treg-specific demethylated region was maintained or even further promoted as was the expression of markers characteristic for nTregs. Moreover, suppressive capacity and the cytokine profile of allogeneic mature monocyte-derived dendritic cell-expanded nTregs was similar to that of healthy individuals. Thus, circulating nTregs of patients with ESRD can effectively be expanded to stable allo antigen-specific nTregs with potential clinical applicability.

Immunomodulatory Effects of Different Lactic Acid Bacteria on Allergic Response and Its Relationship with In Vitro Properties

Some studies reported that probiotic could relieve allergy-induced damage to the host, but how to get a useful probiotic is still a challenge. In this study, the protective effects of three lactic acid bacteria (La, Lp and Lc) were evaluated in a mouse model, and its relationship with the in vitro properties was analyzed. The in vitro results indicated that La with the capacity to inhibit IL-4 production could have a better anti-allergy effect in vivo than two others. However, the animal trials showed that all LAB strains could alleviate allergen-induced airway inflammation. Among them, LAB strain Lp had a better effect in inhibiting allergic response through a modulation of Th1/Th2 balance and an increase of regulatory T cells. This difference could be explained by that different LAB strains have a strain-specific effect on gut microbiota closely associated with host immune responses. Finally, this study did not only obtain an effective anti-allergy probiotic strain via animal study, but also indicate that probiotic-induced effect on intestinal microbiota should be considered as an important screening index, apart from its inherent characteristics.

Chemoattractant Signals and Adhesion Molecules Promoting Human Regulatory T Cell Recruitment to Porcine Endothelium

BACKGROUND

Human CD4+CD25+Foxp3+ T regulatory cells (huTreg) suppress CD4+ T cell-mediated antipig xenogeneic responses in vitro and might therefore be used to induce xenograft tolerance. The present study investigated the role of the adhesion molecules, their porcine ligands, and the chemoattractant factors that may promote the recruitment of huTreg to porcine aortic endothelial cells (PAEC) and their capacity to regulate antiporcine natural killer (NK) cell responses.

METHODS

Interactions between ex vivo expanded huTreg and PAEC were studied by static chemotaxis assays and flow-based adhesion and transmigration assays. In addition, the suppressive function of huTreg on human antiporcine NK cell responses was analyzed.

RESULTS

The TNFα-activated PAEC released factors that induce huTreg chemotaxis, partially inhibited by antihuman CXCR3 blocking antibodies. Coating of PAEC with human CCL17 significantly increased the transmigration of CCR4+ huTreg under physiological shear stress. Under static conditions, transendothelial Treg migration was inhibited by blocking integrin sub-units (CD18, CD49d) on huTreg, or their respective porcine ligands intercellular adhesion molecule 2 (CD102) and vascular cell adhesion molecule 1 (CD106). Finally, huTreg partially suppressed xenogeneic human NK cell adhesion, NK cytotoxicity and degranulation (CD107 expression) against PAEC; however, this inhibition was modest, and there was no significant change in the production of IFNγ.

CONCLUSIONS

Recruitment of huTreg to porcine endothelium depends on particular chemokine receptors (CXCR3, CCR4) and integrins (CD18 and CD49d) and was increased by CCL17 coating. These results will help to develop new strategies to enhance the recruitment of host huTreg to xenogeneic grafts to regulate cell-mediated xenograft rejection including NK cell responses.

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

Expansion of Ag-specific naturally occurring regulatory T cells (nTregs) is required to obtain sufficient numbers of cells for cellular immunotherapy. In this study, different allogeneic stimuli were studied for their capacity to generate functional alloantigen-specific nTregs. A highly enriched nTreg fraction (CD4(+)CD25(bright)CD127(-) T cells) was alloantigen-specific expanded using HLA-mismatched immature, mature monocyte-derived dendritic cells (moDCs), or PBMCs. The allogeneic mature moDC-expanded nTregs were fully characterized by analysis of the demethylation status within the Treg-specific demethylation region of the FOXP3 gene and the expression of both protein and mRNA of FOXP3, HELIOS, CTLA4, and cytokines. In addition, the Ag-specific suppressive capacity of these expanded nTregs was tested. Allogeneic mature moDCs and skin-derived DCs were superior in inducing nTreg expansion compared with immature moDCs or PBMCs in an HLA-DR- and CD80/CD86-dependent way. Remarkably, the presence of exogenous IL-15 without IL-2 could facilitate optimal mature moDC-induced nTreg expansion. Allogeneic mature moDC-expanded nTregs were at low ratios (<1:320), potent suppressors of alloantigen-induced proliferation without significant suppression of completely HLA-mismatched, Ag-induced proliferation. Mature moDC-expanded nTregs were highly demethylated at the Treg-specific demethylation region within the FOXP3 gene and highly expressed of FOXP3, HELIOS, and CTLA4. A minority of the expanded nTregs produced IL-10, IL-2, IFN-γ, and TNF-α, but few IL-17-producing nTregs were found. Next-generation sequencing of mRNA of moDC-expanded nTregs revealed a strong induction of Treg-associated mRNAs. Human allogeneic mature moDCs are highly efficient stimulator cells, in the presence of exogenous IL-15, for expansion of stable alloantigen-specific nTregs with superior suppressive function.

Adoptive T Regulatory Cell Therapy for Tolerance Induction

There is a clear need to develop strategies to induce tolerance without the need of chronic immunosuppression in transplant recipient and in patients with autoimmunity. Adoptive T regulatory cell (T_reg) therapy offers the potential of long-lasting protection. However, based on results of clinical trials so far with ex vivo expanded autologous T_regs in type 1 diabetic (T1D) patients, it seems unlikely that single immunotherapy with T_reg infusion without immunomodulation regimens that promote stable donor T_reg engraftment and persistence would afford truly significant clinical benefit. Combination therapies could provide improved outcomes with consideration of the fundamental factors required for T_reg generation, homeostasis, and function to promote long-term donor T_reg persistence to provoke beneficial therapeutic outcomes.

Enteroviruses, hygiene and type 1 diabetes: toward a preventive vaccine

Enteroviruses and humans have long co-existed. Although recognized in ancient times, poliomyelitis and type 1 diabetes (T1D) were exceptionally rare and not epidemic, due in large part to poor sanitation and personal hygiene which resulted in repeated exposure to fecal-oral transmitted viruses and other infectious agents and viruses and the generation of a broad protective immunity. As a function of a growing acceptance of the benefits of hygienic practices and microbiologically clean(er) water supplies, the likelihood of exposure to diverse infectious agents and viruses declined. The effort to vaccinate against poliomyelitis demonstrated that enteroviral diseases are preventable by vaccination and led to understanding how to successfully attenuate enteroviruses. Type 1 diabetes onset has been convincingly linked to infection by numerous enteroviruses including the group B coxsackieviruses (CVB), while studies of CVB infections in NOD mice have demonstrated not only a clear link between disease onset but an ability to reduce the incidence of T1D as well: CVB infections can suppress naturally occurring autoimmune T1D. We propose here that if we can harness and develop the capacity to use attenuated enteroviral strains to induce regulatory T cell populations in the host through vaccination, then a vaccine could be considered that should function to protect against both autoimmune as well as virus-triggered T1D. Such a vaccine would not only specifically protect from certain enterovirus types but more importantly, also reset the organism's regulatory rheostat making the further development of pathogenic autoimmunity less likely.

Genetically engineered Lactococcus lactis protect against house dust mite allergy in a BALB/c mouse model

Background

Mucosal vaccine based on lactic acid bacteria is an attractive concept for the prevention and treatment of allergic diseases, but their mechanisms of action in vivo are poorly understood. Therefore, we sought to investigate how recombinant major dust mite allergen Der p2-expressing Lactococcus lactis as a mucosal vaccine induced the immune tolerance against house dust mite allergy in a mouse model.

Methods

Three strains of recombinant L. lactis producing Der p2 in different cell components (extracellular, intracellular and cell wall) were firstly constructed. Their prophylactic potential was evaluated in a Der p2-sensitised mouse model, and immunomodulation properties at the cellular level were determined by measuring cytokine production in vitro.

Results

Der p2 expressed in the different recombinant L. lactis strains was recognized by a polyclonal anti-Der p2 antibody. Oral treatment with the recombinant L. lactis prior sensitization significantly prevented the development of airway inflammation in the Der p2-sensitized mice, as determined by the attenuation of inflammatory cells infiltration in the lung tissues and decrease of Th2 cytokines IL-4 and IL-5 levels in bronchoalveolar lavage. In addition, the serum allergen-specific IgE levels were significantly reduced, and the levels of IL-4 in the spleen and mesenteric lymph nodes cell cultures were also markedly decreased upon allergen stimulation in the mice fed with the recombinant L. lactis strains. These protective effects correlated with a significant up-regulation of regulatory T cells in the mesenteric lymph nodes.

Conclusion

Oral pretreatment with live recombinant L. lactis prevented the development of allergen-induced airway inflammation primarily by the induction of specific mucosal immune tolerance.

CD4+ Foxp3+ regulatory T cells in autoimmune orchitis: phenotypic and functional characterization

PROBLEM

The phenotype and function of regulatory T (Treg) cells in rats with experimental autoimmune orchitis (EAO) was evaluated.

METHOD OF STUDY

Distribution of Treg cells in draining lymph nodes from the testis (TLN) and from the site of immunization (ILN) was analysed by immunohistochemistry. The number, phenotype and proliferative response (5-bromo-2'-deoxyuridine incorporation) of Treg cells were evaluated by flow cytometry and Treg cell suppressive activity by in vitro experiments. TGF-β expression was evaluated by immunofluorescence.

RESULTS

Absolute numbers of Treg cells and BrdU+ Treg cells were increased in LN from experimental compared to normal and control rats. These cells displayed a CD45RC(-), CD62L(-), Helios(+) phenotype. CD4(+) CD25(bright) T cells from TLN of experimental rats were able to suppress T cell-proliferation more efficiently than those derived from normal and control rats. Cells isolated from TLN and ILN expressed TGF-β.

CONCLUSION

Our results suggest that Treg cells with a memory/activated phenotype proliferate extensively in the inflamed testis and LN of rats with EAO exhibiting an enhanced suppressive capacity. TGF-β may be involved in their suppressive mechanism.

Improving engraftment and immune reconstitution in umbilical cord blood transplantation

Umbilical cord blood (UCB) is an important source of hematopoietic stem cells (HSC) for allogeneic transplantation when HLA-matched sibling and unrelated donors (MUD) are unavailable. Although the overall survival results for UCB transplantation are comparable to the results with MUD, UCB transplants are associated with slow engraftment, delayed immune reconstitution, and increased opportunistic infections. While this may be a consequence of the lower cell dose in UCB grafts, it also reflects the relative immaturity of cord blood. Furthermore, limited cell numbers and the non-availability of donor lymphocyte infusions currently prevent the use of post-transplant cellular immunotherapy to boost donor-derived immunity to treat infections, mixed chimerism, and disease relapse. To further develop UCB transplantation, many strategies to enhance engraftment and immune reconstitution are currently under investigation. This review summarizes our current understanding of engraftment and immune recovery following UCB transplantation and why this differs from allogeneic transplants using other sources of HSC. It also provides a comprehensive overview of promising techniques being used to improve myeloid and lymphoid recovery, including expansion, homing, and delivery of UCB HSC; combined use of UCB with third-party donors; isolation and expansion of natural killer cells, pathogen-specific T cells, and regulatory T cells; methods to protect and/or improve thymopoiesis. As many of these strategies are now in clinical trials, it is anticipated that UCB transplantation will continue to advance, further expanding our understanding of UCB biology and HSC transplantation.

Regulatory T cells as immunotherapy

Regulatory T cells (Tregs) suppress exuberant immune system activation and promote immunologic tolerance. Because Tregs modulate both innate and adaptive immunity, the biomedical community has developed an intense interest in using Tregs for immunotherapy. Conditions that require clinical tolerance to improve outcomes – autoimmune disease, solid organ transplantation, and hematopoietic stem cell transplantation – may benefit from Treg immunotherapy. Investigators have designed ex vivo strategies to isolate, preserve, expand, and infuse Tregs. Protocols to manipulate Treg populations in vivo have also been considered. Barriers to clinically feasible Treg immunotherapy include Treg stability, off-cell effects, and demonstration of cell preparation purity and potency. Clinical trials involving Treg adoptive transfer to treat graft versus host disease preliminarily demonstrated the safety and efficacy of Treg immunotherapy in humans. Future work will need to confirm the safety of Treg immunotherapy and establish the efficacy of specific Treg subsets for the treatment of immune-mediated disease.

Increased frequency of CD4 and CD8 regulatory T cells in individuals under 15 years with multibacillary leprosy

Background

Leprosy is a chronic disease, caused by Mycobacterium leprae, which poses a serious public health problem worldwide. Its high incidence in people under 15 years old in Ceará state, Brazil, reflects the difficulty of its control. The spectrum of clinical manifestations is associated with the immune response developed, with the Th1 and Th2 responses being related to the paucibacillary and multibacillary forms, respectively. Regulatory T cells (Treg), which can suppress Th1 and Th2 response, have received special attention in the literature and have been associated with development of chronic infections. However, their role in leprosy in individuals under 15 years old has not yet been elucidated. We evaluated the frequency of CD4⁺/CD8⁺CD25^highFOXP3⁺ and CD4⁺/CD8⁺CD25^highFOXP3^high cells in leprosy patients and household contacts, in both cases under 15 years old.

Methodology/Principal Findings

PBMC from 12 patients and 17 contacts were cultured for 72 hours with anti-CD3 and anti-CD28 (activators) or with activators associated with total sonicated fraction of M. leprae. After culture, the frequency of CD4⁺/CD8⁺ Treg was identified by flow cytometry. Cells stimulated by activators and antigen from multibacillary patients showed Treg frequencies almost two times that of the contacts: CD4⁺FOXP3⁺ (21.93±8.43 vs. 13.79±8.19%, p = 0.0500), CD4⁺FOXP3^high (10.33±5.69 vs. 5.57±4.03%, p = 0.0362), CD8⁺FOXP3⁺ (13.88±9.19 vs. 6.18±5.56%, p = 0.0230) and CD8⁺FOXP3^high (5.36±4.17 vs. 2.23±2.68%, p = 0.0461). Furthermore, the mean fluorescence intensity of FOXP3 in Treg was higher in multibacillary patients than in the contacts. Interestingly, there was a positive correlation of the bacillary index and number of lesions with the frequency of all Treg evaluated in patients.

Conclusions/Significance

We have demonstrated for the first time that multibacillary leprosy patients under 15 years old have greater CD4⁺ and CD8⁺ Treg frequencies and these correlate with clinical and laboratorial aspects of disease. These findings suggest the involvement of these cells in the perpetuation of M. leprae infection.

Regulatory T-cell therapy in transplantation: moving to the clinic

Regulatory T cells (Tregs) are essential to transplantation tolerance and their therapeutic efficacy is well documented in animal models. Moreover, human Tregs can be identified, isolated, and expanded in short-term ex vivo cultures so that a therapeutic product can be manufactured at relevant doses. Treg therapy is being planned at multiple transplant centers around the world. In this article, we review topics critical to effective implementation of Treg therapy in transplantation. We will address issues such as Treg dose, antigen specificity, and adjunct therapies required for transplant tolerance induction. We will summarize technical advances in Treg manufacturing and provide guidelines for identity and purity assurance of Treg products. Clinical trial designs and Treg manufacturing plans that incorporate the most up-to-date scientific understanding in Treg biology will be essential for harnessing the tolerogenic potential of Treg therapy in transplantation.

Immunoregulatory pathways are active in the small intestinal mucosa of patients with potential celiac disease

OBJECTIVES

Potential celiac disease (CD) relates to subjects with a normal small intestinal mucosa who are at increased risk of developing CD as indicated by positive CD-associated serology. The objective of this study was to investigate in the small intestinal mucosa of such patients the state of immunological activation with special emphasis on immunoregulatory circuits.

METHODS

Duodenal biopsies from active CD (n=48), potential CD (n=58), and control patients (n=45) were studied. RNA expression for interferon γ (IFNγ) and interleukin-10 (IL-10) were quantified by real-time quantitative PCR. The percentage of CD4+CD25+Foxp3+ T regulatory cells (Foxp3+Tregs) was determinated by flow cytometry and the number of Foxp3+ and IL-15+ cells by immunohistochemistry. Furthermore, we analyzed the suppressive function of CD4+CD25+ T cells, isolated from potential CD biopsy samples, as well as the effect of IL-15, on autologous peripheral blood responder CD4+CD25- T cells.

RESULTS

In potential CD patients with Marsh 1 lesion, IFNγ-RNA expression was significantly less than in active, but enhanced if compared with potential CD patients with Marsh 0 lesion and with controls (P<0.001). The number of IL-15+ cells in subjects with potential CD was increased in comparison with controls (P<0.05), but lower than active CD (P<0.01). IL-10-RNA expression was upregulated in Marsh 0 potential CD patients if compared with those with Marsh 1 lesion (P<0.01) and controls (P<0.001), whereas there were no differences with active CD. The ratio IL-10/IFNγ reached the highest value in Marsh 0 potential CD compared with the other groups (P<0.05). The percentage of Foxp3+Tregs was also higher in potential CD compared with controls (P<0.05), although it was lower than in active CD (P<0.01). In co-culture assay, intestinal CD4+CD25+ T cells from potential CD patients exerted suppressive effects on T responder cells, and their activity was not impaired by IL-15.

CONCLUSIONS

Potential CD patients show a low grade of inflammation that likely could be due to active regulatory mechanisms preventing the progression toward a mucosal damage.

Corticosteroids do not reverse the inhibitory effect of cyclosporine on regulatory T-cell activity in contrast to mycophenolate mofetil

BACKGROUND

Inevitable hepatitis C virus recurrence after liver transplantation, a major barrier to survival of the transplanted liver may be promoted by immunosuppression and by CD4(+)CD25(+) regulatory T cells (Treg). Treg cells are essential for the induction and maintenance of immunologic self-tolerance as well as transplant tolerance. Moreover, we have previously described low doses of cyclosporine (CsA) to inhibit Treg activity by inducing interleukin-2 and interfron-γ. We investigated here in, the effect of mycophenolate mofetil (MMF) and corticosteroids, usually used in combination with a calcineurin inhibitor on human CD4(+)CD25(+) Treg cells.

METHODS

Human CD4(+)CD25(+) cells isolated from healthy donors were cultured in the presence of CsA +/- corticoids or MMF. Suppressive activity of regulatory T cells was assessed in mixed leukocyte reactions including CD25(+) solvents with autologous activated peripheral blood mononuclear cells (PBMC).

RESULTS

MMF and dexamethasone inhibited PBMC and Treg proliferation in dose-dependent fashing, maintaining the suppressive activity of Treg cells. However, the association of corticoids with CsA could not reverse the inhibitory effects of CsA on Treg activity, unlike the MMF and CsA combination.

CONCLUSION

We have previously shown CsA to significantly impair the function of CD4(+)CD25(+) Treg cells. Herein we reports that corticoids were not able to reverse this effect, whereas MMF couterbalanced it, suggesting that the combination of MMF with CsA maintains regulatory T cells activity promoting tolerance.

Regulatory cells and transplantation tolerance

Transplantation tolerance is a continuing therapeutic goal, and it is now clear that a subpopulation of T cells with regulatory activity (Treg) that express the transcription factor foxp3 are crucial to this aspiration. Although reprogramming of the immune system to donor-specific transplantation tolerance can be readily achieved in adult mouse models, it has yet to be successfully translated in human clinical practice. This requires that we understand the fundamental mechanisms by which donor antigen-specific Treg are induced and function to maintain tolerance, so that we can target therapies to enhance rather than impede these regulatory processes. Our current understanding is that Treg act via numerous molecular mechanisms, and critical underlying components such as mTOR inhibition, are only now emerging.

Functional defect in regulatory T cells in myasthenia gravis

Forkhead box P3 (FOXP3) is a transcription factor necessary for the function of regulatory T cells (T(reg) cells). T(reg) cells maintain immune homeostasis and self-tolerance and play an important role in the prevention of autoimmune disease. Here, we discuss the role of T(reg) cells in the pathogenesis of myasthenia gravis (MG) and review evidence indicating that a significant defect in T(reg) cell in vitro suppressive function exists in MG patients, without an alteration in circulating frequency. This functional defect is associated with a reduced expression of key functional molecules, such as FOXP3 on isolated T(reg) cells, and appears to be more pronounced in immunosuppression-naive MG patients. In vitro administration of granulocyte macrophage-colony-stimulating factor (GM-CSF) enhanced the suppressive function of T(reg) cells and upregulated FOXP3 expression. These findings indicate a clinically relevant T(reg) cell-intrinsic defect in immune regulation in MG that may reveal a novel therapeutic target.

Identification of tribbles-1 as a novel binding partner of Foxp3 in regulatory T cells

In a previous study, we identified TRIB1, a serine-threonine kinase-like molecule, as a biomarker of chronic antibody-mediated rejection of human kidneys when measured in peripheral blood mononuclear cells. Here, we focused our analysis on a specific subset of peripheral blood mononuclear cells that play a dominant role in regulating immune responses in health and disease, so-called CD4(+)CD25(+)Foxp3(+) regulatory T cells (Tregs). We isolated both human and murine Treg and non-Treg counterparts and analyzed TRIB1 and Foxp3 mRNA expression by quantitative PCR on the freshly isolated cells or following 24 h of activation. Physical interaction between the human TRIB1 and Foxp3 proteins was analyzed in live cell lines by protein complementation assay using both flow cytometry and microscopy and confirmed in primary freshly isolated human CD4(+)CD25(hi)CD127(-) Tregs by co-immunoprecipitation. Both TRIB1 and Foxp3 were expressed at significantly higher levels in Tregs than in their CD4(+)CD25(-) counterparts (p < 0.001). Moreover, TRIB1 and Foxp3 mRNA levels correlated tightly in Tregs (Spearman r = 1.0; p < 0.001, n = 7), but not in CD4(+)CD25(-) T cells. The protein complementation assay revealed a direct physical interaction between TRIB1 and Foxp3 in live cells. This interaction was impaired upon deletion of the TRIB1 N-terminal but not the C-terminal domain, suggesting an interaction in the nucleus. This direct interaction within the nucleus was confirmed in primary human Tregs by co-immunoprecipitation. These data show a direct relationship between TRIB1 and Foxp3 in terms of their expression and physical interaction and highlight Tribbles-1 as a novel binding partner of Foxp3 in Tregs.

Manifestations of immune tolerance in the human female reproductive tract

Like other mucosal surfaces (e.g., the gastrointestinal tract, the respiratory tract), the human female reproductive tract acts as an initial barrier to foreign antigens. In this role, the epithelial surface and subepithelial immune cells must balance protection against pathogenic insults against harmful inflammatory reactions and acceptance of particular foreign antigens. Two common examples of these acceptable foreign antigens are the fetal allograft and human semen/sperm. Both are purposely deposited into the female genital tract and appropriate immunologic response to these non-self antigens is essential to the survival of the species. In light of the weight of this task, it is not surprising that multiple, redundant and overlapping mechanisms are involved. For instance, cells at the immunologic interface between self (female reproductive tract epithelium) and non-self (placental trophoblast cells or human sperm) express glycosylation patterns that mimic those on many metastatic cancer cells and successful pathogens. The cytokine/chemokine milieu at this interface is altered through endocrine and immunologic mechanisms to favor tolerance of non-self. The “foreign” cells themselves also play an integral role in their own immunologic acceptance, since sperm and placental trophoblast cells are unusual and unique in their antigen presenting molecule expression patterns. Here, we will discuss these and other mechanisms that allow the human female reproductive tract to perform this delicate and indispensible balancing act.

IL-7 abrogates suppressive activity of human CD4+CD25+FOXP3+ regulatory T cells and allows expansion of alloreactive and autoreactive T cells

CD4(+)CD25(+)FOXP3(+) regulatory T cells (Tregs) control the activation and expansion of alloreactive and autoreactive T cell clones. Because uncontrolled activation and expansion of autoreactive T cells occur in an IL-7-rich environment, we explored the possibility that IL-7 may affect the function of Treg. We show that the functional high-affinity IL-7R is expressed on both naive and memory Tregs, and exposure to IL-7 results in STAT-5 phosphorylation. Naive, but not memory, Tregs proliferated greatly and acquired a memory phenotype in the setting of a suppression assay when IL-7 was present. Importantly, the presence of IL-7 abrogated the capacity of Tregs to suppress proliferation of conventional T cells in response to TCR activators, including alloantigens and autoantigens. Removal of IL-7 restored the suppressive function of Tregs. Preblocking of the IL-7R on the Tregs also restored suppressor function, indicating that IL-7 directly affected Treg function. Thus, prolonged periods of homeostatic expansion can temporarily release natural regulatory brakes on T cells, thereby providing an additional mechanism for activating and expanding alloreactive and autoreactive T cells.

In vitro effects of cyclosporine A and tacrolimus on regulatory T-cell proliferation and function

BACKGROUND

Liver transplantation is the treatment of end-stage liver diseases, including hepatitis C. Immunosuppression prevents graft rejection but seems to accelerate the recurrence of hepatitis C. Regulatory T cells (Tregs) may be beneficial in tolerance but deleterious in recurrent hepatitis C. We evaluated the effects of cyclosporine or tacrolimus, the principal immunosuppressive drugs, on Treg proliferation and function.

METHODS

Human Tregs were isolated from healthy donors and cultured with cyclosporine, tacrolimus, or NIM811, a cyclosporine analog devoid of calcineurin-inhibiting activity. Treg proliferation and suppressive activity were assessed. The phenotype, cytokine production, and phosphorylation profile of nuclear factor of activated T cell of Tregs were also analyzed.

RESULTS

Cyclosporine and tacrolimus both decreased Treg proliferation, but only low doses of cyclosporine reduced Treg activity, by inducing the production of interleukin 2 proinflammatory cytokines in these cells. Moreover, NIM811 also inhibited Treg activity. The phosphorylation of nuclear factor of activated T cell in Tregs was not altered by cyclosporine, suggesting that the effects of this drug are independent of the calcineurin pathway.

CONCLUSION

In summary, low doses of cyclosporine inhibit Treg activity, a finding that might explain the beneficial effect of this drug on hepatitis C recurrence. In contrast, by maintaining Treg activity, tacrolimus could be more helpful than cyclosporine in controlling rejection.

CD26: a negative selection marker for human Treg cells

A major obstacle hampering the therapeutic application of regulatory T (Treg) cells is the lack of suitable extracellular markers, which complicates their identification/isolation. Treg cells are normally isolated via CD25 (IL-2Rα) targeting, but this protein is also expressed by activated CD4(+) effector T (Teff) lymphocytes. Other extracellular (positive or negative) Treg selection markers (e.g., HLA-DR, CD127) are also nonspecific. CD26 is an extracellular peptidase whose high expression has been traditionally used as an indicator of immune activation and effector functions in T cells. Now, we provide flow cytometry data showing high levels of CD26 within CD4(+)CD25(-) or CD4(+)FoxP3(-/low) effector T (Teff) lymphocytes, but negative or low levels (CD26(-/low)) in Treg cells selected according to the CD4(+)CD25(high) or the CD4(+)FoxP3(high) phenotype. Unlike the negative marker CD127 (IL-7Rα), which is down modulated in CD4(+) Teff lymphocytes after TCR triggering, most of these cells upregulate CD26 and take a CD4(+)CD25(+/high) CD26(+) phenotype upon activation. In contrast, there is only a slight upregulation within Treg cells (CD4(+)CD25(high) CD26(-/low)). Thus, differences in CD26 levels between Treg and Teff subsets are stable, and assessment of this marker, in combination with others like CD25, FoxP3, or CD127, may be useful during the quantitative evaluation or the isolation of Treg cells in samples containing activated Teff lymphocytes (e.g., from patients with autoimmune/inflammatory diseases).

Changes in chemokine receptor expression of regulatory T cells after ex vivo culture

By controlling and limiting inflammatory conditions, naturally occurring regulatory T cells (Tregs), defined as circulating CD4(+)CD25(bright)FoxP3(+) cells, play critical roles in maintaining tolerance and preventing autoimmunity and thus have tremendous potential for adoptive immunotherapy. Because they represent a scanty subset of the CD4(+) T-lymphocyte subset, several approaches have been developed to isolate and expand ex vivo polyclonal Tregs. However, one limitation of the functional analyses performed on these cultured Tregs is the incomplete characterization of their tissue-trafficking properties. As this aspect provides crucial information for their therapeutic effects, we have here explored the chemokine receptor expression profile and function of Tregs cultured ex vivo with validated expansion protocols. Our data show that ex vivo cultured Tregs retained the expression of CCR7 but dramatically downregulated CCR5 as compared with freshly isolated Tregs. The differential chemokine receptors expression pattern corroborated with their respective steady state messenger RNA expression and also with their migration toward specific chemokines. Our analyses suggest that ex vivo cultured Tregs may display impaired or suboptimal migration to the inflamed tissues releasing RANTES and MIP-1α chemokines.

Ex-vivo expanded baboon CD4+ CD25 Hi Treg cells suppress baboon anti-pig T and B cell immune response

BACKGROUND

CD4(+) CD25(+) FoxP3(+) regulatory T (Treg) cells play an important role in regulating immune responses. A very small number of Treg cells are present in peripheral blood and lymphoid organs, but due to their ability to suppress the immune response, they have a high potential for immunotherapy in clinics. Successful ex-vivo expansion of naturally occurring CD4(+) CD25(+) T cells has been achieved after TCR stimulation in the presence of T cell growth factors. In this study, we evaluated the role of these Treg cells in suppressing proliferative response of baboon T and B cells to pig xenoantigens.

METHODS

Naturally occurring baboon CD4(+) CD25(+) regulatory T cells (nTreg) were sorted from peripheral blood and expanded in the presence of either anti-CD3/CD28 beads or irradiated pig peripheral blood mononuclear cells with IL-2. Treg cells were also enriched directly from CD4(+) T cells cultured in the presence of rapamycin (0.1-10 nm). Mixed lymphocyte culture and polyclonal B cell stimulation with ex-vivo Treg cells were performed to assess the function of ex-vivo expanded Treg cells.

RESULTS

The nTreg cells were expanded to more than 200-fold in 4 weeks and retained all the nTreg cell phenotypic characteristics, including high levels of FoxP3 expression. 2-fold increase in enrichment of CD4(+) CD25(+) FoxP3(+) Treg cells from CD4(+) cells was observed with rapamycin compared to cultures without rapamycin. The ex-vivo expanded Treg cells obtained from both methods were able to suppress the baboon anti-porcine xenogeneic T and B cell immune response in-vitro efficiently (more than 90% suppression at 1:1 ratio of T regulatory cells: T effector cells), and their suppression potential was retained even at 1:256 ratio. However, freshly isolated nTreg cells had only 70% suppression at 1:1 ratio, and their suppressive ability was reduced to ≤ 50% at 1:16 ratio. Furthermore, we have found that ex-vivo expanded Treg can also suppress the proliferation of B cells after polyclonal stimulation. Forty to 50 percent reduction in B cell proliferation was observed when ex-vivo expanded Treg cells were added to the culture at a 1:1 ratio. The addition of CD4(+) CD25(Neg) cells however induced vigorous proliferation.

CONCLUSION

Ex-vivo expanded CD4(+) CD25(+) FoxP3(+) Treg cells can be used to efficiently suppress xenogeneic immune responses by inhibiting T and B cell proliferation. These ex-vivo expanded Treg cells may also be used with other immunosuppressive agents to overcome xenograft rejection in preclinical xenotransplantation models.

TCR affinity and specificity requirements for human regulatory T-cell function

We investigated whether TCRs restricted to the more ubiquitously expressed MHC class I molecules could be used to redirect human regulatory T cells (Tregs). Using a series of HLA-A2-restricted TCRs that recognize the same peptide-MHC class I complex (pMHC) with affinities varying up to 3500 fold, we observed that TCR affinity had no effect on the ability of the introduced TCRs to confer potent Ag-specific suppressive activity. Surprisingly, we found a naturally occurring, low-affinity MHC class I-restricted TCR specific for an NY-ESO-1 epitope that was unable to redirect a functional CD4 T-effector cell response could confer potent antigen-specific suppressive activity when expressed in Tregs and severely impair the expansion of highly functional HIV-1(GAG)-specific CD8 T cells expressing a high-affinity TCR. This suppressive activity was only observed when both Ags were presented by the same cell, and no suppression was observed when the target Ags were put in distinct cells. These studies underscore the clinical utility of using MHC class I-restricted TCRs to endow Tregs with specificity to control autoimmune disease and highlight the conditions in which this approach would have most therapeutic benefit.

CD4(+)Foxp3(+) regulatory T cell therapy in transplantation

Regulatory T cells (Tregs) are long-lived cells that suppress immune responses in vivo in a dominant and antigen-specific manner. Therefore, therapeutic application of Tregs to control unwanted immune responses is an active area of investigation. Tregs can confer long-term protection against auto-inflammatory diseases in mouse models. They have also been shown to be effective in suppressing alloimmunity in models of graft-versus-host disease and organ transplantation. Building on extensive research in Treg biology and preclinical testing of therapeutic efficacy over the past decade, we are now at the point of evaluating the safety and efficacy of Treg therapy in humans. This review focuses on developing therapy for transplantation using CD4(+)Foxp3(+) Tregs, with an emphasis on the studies that have informed clinical approaches that aim to maximize the benefits while overcoming the challenges and risks of Treg cell therapy.

Amelioration of acute graft-versus-host disease by adoptive transfer of ex vivo expanded human cord blood CD4+CD25+ forkhead box protein 3+ regulatory T cells is associated with the polarization of Treg/Th17 balance in a mouse model

BACKGROUND

Human cord blood (CB) is a superior source of regulatory T cells (Tregs) compared with peripheral blood. Initial studies have shown that CB-derived Tregs can be effectively expanded ex vivo. However, in vitro suppressor activity of expanded CB-Tregs and their efficacy in the prevention of acute graft-versus-host disease (aGVHD) in vivo are poorly understood.

STUDY DESIGN AND METHODS

In vitro, human CB CD4+CD25+ T cells expanded with anti-CD3/CD28 beads plus interleukin (IL)-2 and the phenotypes, expression of cytokines, and suppression of expanded cells were analyzed after two cycles of stimulation. In vivo, the addition of human CB-Tregs was transferred in the major histocompatibility complex-mismatched aGVHD mouse model. Survival, body weight, GVHD scoring, histopathologic specimens, serum cytokines, and Th subsets were analyzed in CB-Treg-treated mice and untreated controls.

RESULTS

After being expanded ex vivo, human CB-derived Tregs with potent suppressor function could meet clinical demands. Up to 85% of mice with CB-Tregs treatment survived beyond Day 63 after bone marrow transplantation; however, all aGVHD mice died within 18 days. In the serum of the CB-Treg-treated mice, the production of transforming growth factor-β increased continuously, as opposed to IL-17, which decreased quickly. Consistent with the changes of cytokines, the percentage of mouse CD4+ forkhead box protein 3+ Tregs increased while that of Th17 cells decreased.

CONCLUSION

Ex vivo expanded human CB-Tregs significantly prevented allogeneic aGVHD in vivo by modulating various cytokine secretion and polarizing the Treg/Th17 balance toward Treg, which suggests the potential use of expanded CB-Tregs as a therapeutic approach for GVHD.

GM-CSF-induced regulatory T cells selectively inhibit anti-acetylcholine receptor-specific immune responses in experimental myasthenia gravis

We and others have demonstrated the ability of granulocyte-macrophage colony-stimulating factor (GM-CSF) to suppress autoimmunity by increasing the number of CD4(+)CD25(+) regulatory T cells (Tregs). In the current study, we have explored the critical role of induced antigen specific Tregs in the therapeutic effects of GM-CSF in murine experimental autoimmune myasthenia gravis (EAMG). Specifically, we show that Tregs from GM-CSF treated EAMG mice (GM-CSF/AChR-induced-Tregs) adoptively transferred into animals with EAMG suppressed clinical disease more potently than equal numbers of Tregs from either GM-CSF untreated EAMG mice or healthy mice treated with GM-CSF. In addition, GM-CSF/AChR-induced-Tregs selectively suppressed antigen specific T cell proliferation induced by AChR relative to that induced by an irrelevant self antigen, (thyroglobulin) and failed to significantly alter T cell proliferation in response to an exogenous antigen (ovalbumin). These results are consistent with the hypothesized mechanism of action of GM-CSF involving the mobilization of tolerogenic dendritic cell precursors which, upon antigen (AChR) capture, suppress the anti-AChR immune response through the induction/expansion of AChR-specific Tregs.

Isolation, expansion and functional assessment of CD4+CD25+FoxP3+ regulatory T cells and Tr1 cells from uremic patients awaiting kidney transplantation

BACKGROUND

The immunosuppressive properties of regulatory T cells have emerged as an attractive tool for the development of immunotherapies in various disease contexts, e.g. to treat transplantation induced immune reactions. This paper focuses on the process of obtaining and functionally characterizing CD4+CD25+FoxP3+ regulatory T cells and Tr1 cells from uremic patients awaiting kidney transplantation.

METHODS

From October 2010 to March 2011 uremic patients awaiting living donor kidney transplantation, and their corresponding kidney donors, were enrolled in the study. A total of seven pairs were included. Isolation of CD4+CD25+FoxP3+ regulatory T cells was performed by magnetic activated cell sorting of peripheral blood mononuclear cells obtained from the uremic patients. Donor specific Tr1 cells were differentiated by repetitive stimulation of immature CD4+ T cells with immature dendritic cells, with the T cells coming from the future kidney recipients and the dendritic cells from the corresponding kidney donors. Cells were then expanded and functionally characterized by the one-way mixed leukocyte reaction and assessment of IL-10 production. Phenotypic analysis was performed by flow cytometry.

RESULTS

The fraction of CD4+CD25+FoxP3+ regulatory T cells after expansion varied from 39.1 to 50.4% and the cells retained their ability to substantially suppress the mixed leukocyte reaction in all but one patient (3.8-19.2% of the baseline stimulated leukocyte activity, p<0.05). Tr1 cells were successfully differentiated from all but one patient and produced high levels of IL-10 when stimulated with immature dendritic cells (1,275-11,038% of the baseline IL-10 secretion, p<0.05).

CONCLUSION

It is practically feasible to obtain and subsequently expand CD4+CD25+FoxP3+ regulatory T cells and Tr1 cells from uremic patients without loss of function as assessed by in vitro analyses. This forms a base for adoptive regulatory T cell therapy in the setting of living donor kidney transplantation.

Foxp3+-inducible regulatory T cells suppress endothelial activation and leukocyte recruitment

The ability of regulatory T cells (Treg) to traffic to sites of inflammation supports their role in controlling immune responses. This feature supports the idea that adoptive transfer of in vitro expanded human Treg could be used for treatment of immune/inflammatory diseases. However, the migratory behavior of Treg, as well as their direct influence at the site of inflammation, remains poorly understood. To explore the possibility that Treg may have direct anti-inflammatory influences on tissues, independent of their well-established suppressive effects on lymphocytes, we studied the adhesive interactions between mouse Treg and endothelial cells, as well as their influence on endothelial function during acute inflammation. We show that Foxp3(+) adaptive/inducible Treg (iTreg), but not naturally occurring Treg, efficiently interact with endothelial selectins and transmigrate through endothelial monolayers in vitro. In response to activation by endothelial Ag presentation or immobilized anti-CD3ε, Foxp3(+) iTreg suppressed TNF-α- and IL-1β-mediated endothelial selectin expression and adhesiveness to effector T cells. This suppression was contact independent, rapid acting, and mediated by TGF-β-induced activin receptor-like kinase 5 signaling in endothelial cells. In addition, Foxp3(+) iTreg adhered to inflamed endothelium in vivo, and their secretion products blocked acute inflammation in a model of peritonitis. These data support the concept that Foxp3(+) iTreg help to regulate inflammation independently of their influence on effector T cells by direct suppression of endothelial activation and leukocyte recruitment.

Moving to tolerance: clinical application of T regulatory cells

Decreasing the incidence of chronic rejection and reducing the need for life-long immunosuppression remain important goals in clinical transplantation. In this article, we will review how regulatory T cells (Treg) came to be recognized as an attractive way to prevent or treat allograft rejection, the ways in which Treg can be manipulated or expanded in vivo, and the potential of in vitro expanded/generated Treg for cellular therapy. We will describe the first regulatory T cell therapies that have been or are in the process of being conducted in the clinic as well as the safety concerns of such therapies and how outcomes may be measured.

Generation and function of immunosuppressive human and murine CD8+ T cells by transforming growth factor-β and retinoic acid

The intestinal immune system is constantly challenged by foreign antigens and commensal bacteria. Therefore, proper control of the intestinal microenvironment is required. One important arm of this regulatory network consists of regulatory T cells. In contrast to CD4(+) Foxp3(+) regulatory T cells, which have been well characterized, immunomodulatory CD8(+) T cells that express Foxp3 are less well defined in terms of their generation and function. Failures of these regulatory mechanisms contribute to the development of inflammatory bowel disease. In this study we demonstrate that the frequency of CD8(+) Foxp3(+) T cells is reduced in the peripheral blood of patients with ulcerative colitis. As these cells might play a currently underestimated role in the maintenance of intestinal homeostasis, we have investigated human and murine CD8(+) Foxp3(+) T cells generated by stimulating naive CD8(+) T cells in the presence of transforming growth factor-β and retinoic acid, mediators that are abundantly produced in the intestinal mucosa. These CD8(+) Foxp3(+) fully competent regulatory T cells show strong expression of regulatory molecules CD25, Gpr83 and CTLA-4 and exhibit cell-cell contact-dependent immunosuppressive activity in vitro. Our study illustrates a previously unappreciated critical role of CD8(+) Foxp3(+) T cells in controlling potentially dangerous T cells and in the maintenance of intestinal homeostasis.

Cutting edge: Human regulatory T cells require IL-35 to mediate suppression and infectious tolerance

Human regulatory T cells (T(reg)) are essential for the maintenance of immune tolerance. However, the mechanisms they use to mediate suppression remain controversial. Although IL-35 has been shown to play an important role in T(reg)-mediated suppression in mice, recent studies have questioned its relevance in human T(reg). In this study, we show that human T(reg) express and require IL-35 for maximal suppressive capacity. Substantial upregulation of EBI3 and IL12A, but not IL10 and TGFB, was observed in activated human T(reg) compared with conventional T cells (T(conv)). Contact-independent T(reg)-mediated suppression was IL-35 dependent and did not require IL-10 or TGF-β. Lastly, human T(reg)-mediated suppression led to the conversion of the suppressed T(conv) into iTr35 cells, an IL-35-induced T(reg) population, in an IL-35-dependent manner. Thus, IL-35 contributes to human T(reg)-mediated suppression, and its conversion of suppressed target T(conv) into IL-35-induced T(reg) may contribute to infectious tolerance.