Antigen-dependent suppression of alloresponses byFoxp3-induced regulatory T cells in transplantation

Chronic GvHD NIH Consensus Project Biology Task Force: evolving path to personalized treatment of chronic GvHD

Chronic graft-versus-host disease (cGvHD) remains a prominent barrier to allogeneic hematopoietic stem cell transplantion as the leading cause of nonrelapse mortality and significant morbidity. Tremendous progress has been achieved in both the understanding of pathophysiology and the development of new therapies for cGvHD. Although our field has historically approached treatment from an empiric position, research performed at the bedside and bench has elucidated some of the complex pathophysiology of cGvHD. From the clinical perspective, there is significant variability of disease manifestations between individual patients, pointing to diverse biological underpinnings. Capitalizing on progress made to date, the field is now focused on establishing personalized approaches to treatment. The intent of this article is to concisely review recent knowledge gained and formulate a path toward patient-specific cGvHD therapy.

FOXP3 mRNA Profile Prognostic of Acute T Cell-mediated Rejection and Human Kidney Allograft Survival

BACKGROUND

T cell-mediated rejection (TCMR) is the most frequent type of acute rejection and is associated with kidney allograft failure. Almost 40% of TCMR episodes are nonresponsive to therapy, and molecular mechanisms for the nonresponsiveness are unknown. Our single-center study identified that urinary cell FOXP3 mRNA abundance predicts TCMR reversibility and allograft survival.

METHODS

We developed PCR assays and measured absolute copy numbers of transcripts for FOXP3, CD25, CD3E, perforin, and 18S rRNA in 3559 urines from 480 kidney allograft recipients prospectively enrolled in the multicenter Clinical Trials in Organ Transplantation-04. In this replication study, we investigated the association between mRNA profile and TCMR diagnosis, TCMR reversibility, and allograft survival.

RESULTS

18S rRNA normalized levels of mRNA for FOXP3 (P = 0.01, Kruskal-Wallis test), CD25 (P = 0.01), CD3E (P < 0.0001), and perforin (P < 0.0001) were diagnostic of TCMR, but only FOXP3 mRNA level predicted TCMR reversibility (ROC AUC = 0.764; 95% confidence interval, 0.611-0.917; P = 0.008). Multivariable logistic regression analyses showed that urinary cell FOXP3 mRNA level predicted reversal, independent of clinical variables. A composite model of clinical variables and FOXP3 mRNA (AUC = 0.889; 95% CI, 0.781-0.997; P < 0.001) outperformed FOXP3 mRNA or clinical variables in predicting TCMR reversibility (P = 0.01, likelihood ratio test). Multivariable Cox proportional hazards regression analyses showed that FOXP3 mRNA level predicts kidney allograft survival (P = 0.047) but not after controlling for TCMR reversal (P = 0.477).

CONCLUSIONS

Urinary cell level of FOXP3 mRNA is diagnostic of TCMR, predicts TCMR reversibility, and is prognostic of kidney allograft survival via a mechanism involving TCMR reversal.

Chimeric antigen receptor-engineered regulatory T lymphocytes: promise for immunotherapy of autoimmune disease

Regulatory T lymphocytes (Tregs) exist as natural ideal immunosuppressors in the immune system. Autologous or allogeneic Treg transfusion therapy has been carried out in animal models and humans as a new strategy for treating autoimmune disease. Recent studies have shown that Tregs can be engineered with chimeric antigen receptors to be antigen-specific, which are more effective than polyclonal Tregs with fewer target limitations and a lack of major histocompatibility complex restriction. This review describes the potential for applying chimeric antigen receptor-engineered regulatory T cells in autoimmune diseases.

Regulatory T cells and asthma

Asthma is a chronic disease of airway inflammation due to excessive T helper cell type 2 (Th2) response. Present treatment based on inhalation of synthetic glucocorticoids can only control Th2-driven chronic eosinophilic inflammation, but cannot change the immune tolerance of the body to external allergens. Regulatory T cells (Tregs) are the main negative regulatory cells of the immune response. Tregs play a great role in regulating allergic, autoimmune, graft-versus-host responses, and other immune responses. In this review, we will discuss the classification and biological characteristics, the established immunomodulatory mechanisms, and the characteristics of induced differentiation of Tregs. We will also discuss the progress of Tregs in the field of asthma. We believe that further studies on the regulatory mechanisms of Tregs will provide better treatments and control strategies for asthma.

Early Growth Response Gene 2-Expressing CD4+LAG3+ Regulatory T Cells: The Therapeutic Potential for Treating Autoimmune Diseases

Regulatory T cells (Tregs) are necessary for the maintenance of immune tolerance. Tregs are divided into two major populations: one is thymus derived and the other develops in the periphery. Among these Tregs, CD4⁺CD25⁺ Tregs, which mainly originate in the thymus, have been extensively studied. Transcription factor Foxp3 is well known as a master regulatory gene for the development and function of CD4⁺CD25⁺ Tregs. On the other hand, peripheral Tregs consist of distinct cell subsets including Foxp3-dependent extrathymically developed Tregs and interleukin (IL)-10-producing type I regulatory T (Tr1) cells. Lymphocyte activation gene 3 (LAG3) and CD49b are reliable cell surface markers for Tr1 cells. CD4⁺CD25⁻LAG3⁺ Tregs (LAG3⁺ Tregs) develop in the periphery and produce a large amount of IL-10. LAG3⁺ Tregs characteristically express the early growth response gene 2 (Egr2), a zinc-finger transcription factor, and exhibit its suppressive activity in a Foxp3-independent manner. Although Egr2 was known to be essential for hindbrain development and myelination of the peripheral nervous system, recent studies revealed that Egr2 plays vital roles in the induction of T cell anergy and also the suppressive activities of LAG3⁺ Tregs. Intriguingly, forced expression of Egr2 converts naive CD4⁺ T cells into IL-10-producing Tregs that highly express LAG3. Among the four Egr gene family members, Egr3 is thought to compensate for the function of Egr2. Recently, we reported that LAG3⁺ Tregs suppress humoral immune responses via transforming growth factor β3 production in an Egr2- and Egr3-dependent manner. In this review, we focus on the role of Egr2 in Tregs and also discuss its therapeutic potential for the treatment of autoimmune diseases.

Posttransplant chimeric antigen receptor therapy

Therapeutic T-cell engineering is emerging as a powerful approach to treat refractory hematological malignancies. Its most successful embodiment to date is based on the use of second-generation chimeric antigen receptors (CARs) targeting CD19, a cell surface molecule found in most B-cell leukemias and lymphomas. Remarkable complete remissions have been obtained with autologous T cells expressing CD19 CARs in patients with relapsed, chemo-refractory B-cell acute lymphoblastic leukemia, chronic lymphocytic leukemia, and non-Hodgkin lymphoma. Allogeneic CAR T cells may also be harnessed to treat relapse after allogeneic hematopoietic stem cell transplantation. However, the use of donor T cells poses unique challenges owing to potential alloreactivity. We review different approaches to mitigate the risk of causing or aggravating graft-versus-host disease (GVHD), including CAR therapies based on donor leukocyte infusion, virus-specific T cells, T-cell receptor-deficient T cells, lymphoid progenitor cells, and regulatory T cells. Advances in CAR design, T-cell selection and gene editing are poised to enable the safe use of allogeneic CAR T cells without incurring GVHD.

Current strategies to improve the safety of chimeric antigen receptor (CAR) modified T cells

Adoptive immunotherapy adopting chimeric antigen receptor (CAR) modified T cells has arisen attention as a hard-hitting therapy for numerous cancers. CARs are genetically engineered receptors that could stimulate tumor cytotoxicity once binding to the specific tumor epitopes. In spite of current noteworthy achievements in hematologic malignancies, the safety problems have aroused public awareness. In this review, we will focus on recent potential strategies to improve the security of CAR modified T cells.

Unique patterns of CD8+ T-cell-mediated organ damage in the Act-mOVA/OT-I model of acute graft-versus-host disease

T-cell receptor (TCR)-transgenic models of acute graft-versus-host disease (aGvHD) offer a straightforward and highly controlled approach to study the mechanisms and consequences of T-cell activation following allogeneic hematopoietic stem cell transplantation (aHSCT). Here, we report that aHSCT involving OT-I mice as donors, carrying an ovalbumin-specific CD8+ TCR, and Act-mOVA mice as recipients, expressing membrane-bound ovalbumin driven by the β-actin promoter, induces lethal aGvHD in a CD8+ T-cell-dependent, highly reproducible manner, within 4-7 days. Tracking of UBC-GFP/OT-I graft CD8+ T cells disclosed heavy infiltration of the gastrointestinal tract, liver, and lungs at the onset of the disease, and histology confirmed hallmark features of gastrointestinal aGVHD, hepatic aGvHD, and aGvHD-associated lymphocytic bronchitis in infiltrated organs. However, T-cell infiltration was virtually absent in the skin, a key target organ of human aGvHD, and histology confirmed the absence of cutaneous aGVHD, as well. We show that the model allows studying CD8+ T-cell responses in situ, as selective recovery of graft CD45.1/OT-I CD8+ T cells from target organs is simple and feasible by automated tissue dissociation and subsequent cell sorting. Assessment of interferon-gamma production by flow cytometry, granzyme-B release by ELISA, TREC assay, and whole-genome gene expression profiling confirmed that isolated graft CD8+ T cells remained intact, underwent clonal expansion, and exerted effector functions in all affected tissues. Taken together, these data demonstrate that the OT-I/Act-mOVA model is suitable to study the CD8+ T-cell-mediated effector mechanisms in a disease closely resembling fatal human gastrointestinal and hepatic aGVHD that may develop after aHSCT using HLA-matched unrelated donors.

HY-Specific Induced Regulatory T Cells Display High Specificity and Efficacy in the Prevention of Acute Graft-versus-Host Disease

Naturally derived regulatory T cells (Tregs) may prevent graft-versus-host disease (GVHD) while preserving graft-versus-leukemia (GVL) activity. However, clinical application of naturally derived regulatory T cells has been severely hampered by their scarce availability and nonselectivity. To overcome these limitations, we took alternative approaches to generate Ag-specific induced Tregs (iTregs) and tested their efficacy and selectivity in the prevention of GVHD in preclinical models of bone marrow transplantation. We selected HY as a target Ag because it is a naturally processed, ubiquitously expressed minor histocompatibility Ag (miHAg) with a proven role in GVHD and GVL effect. We generated HY-specific iTregs (HY-iTregs) from resting CD4 T cells derived from TCR transgenic mice, in which CD4 cells specifically recognize HY peptide. We found that HY-iTregs were highly effective in preventing GVHD in male (HY(+)) but not female (HY(-)) recipients using MHC II-mismatched, parent→F1, and miHAg-mismatched murine bone marrow transplantation models. Interestingly, the expression of target Ag (HY) on the hematopoietic or nonhematopoietic compartment alone was sufficient for iTregs to prevent GVHD. Furthermore, treatment with HY-iTregs still preserved the GVL effect even against pre-established leukemia. We found that HY-iTregs were more stable in male than in female recipients. Furthermore, HY-iTregs expanded extensively in male but not female recipients, which in turn significantly reduced donor effector T cell expansion, activation, and migration into GVHD target organs, resulting in effective prevention of GVHD. This study demonstrates that iTregs specific for HY miHAgs are highly effective in controlling GVHD in an Ag-dependent manner while sparing the GVL effect.

The Free Radical Scavenger NecroX-7 Attenuates Acute Graft-versus-Host Disease via Reciprocal Regulation of Th1/Regulatory T Cells and Inhibition of HMGB1 Release

Graft-versus-host disease (GVHD) is a major complication associated with allogeneic hematopoietic stem cell transplantation. Despite the prominent role of the adaptive immune system, the importance of controlling the innate immune system in the pathogenesis of GVHD has recently been rediscovered. High-mobility group box 1 (HMGB1) is a crucial damage-associated molecular pattern signal that functions as a potent innate immune mediator in GVHD. In the present study, we investigated treatment of experimental GVHD through HMGB1 blockade using the compound cyclopentylamino carboxymethylthiazolylindole (NecroX)-7. Treated animals significantly attenuated GVHD-related mortality and inhibited severe tissue damage. These protective effects correlated with the decrease in HMGB1 expression and lower levels of reactive oxidative stress. Additionally, NecroX-7 inhibited the HMGB1-induced release of TNF and IL-6, as well as the expression of TLR-4 and receptor for advanced glycation end products. We also observed increased regulatory T cell numbers, which may be associated with regulation of differentiation signals independent of HMGB1. Taken together, these data indicate that NecroX-7 protects mice against lethal GVHD by reciprocal regulation of regulatory T/Th1 cells, attenuating systemic HMGB1 accumulation and inhibiting HMGB1-mediated inflammatory response. Our results indicate the possibility of a new use for a clinical drug that is effective for the treatment of GVHD.

Regulatory T cells in children with allergy and asthma: it is time to act

Nowadays allergy and asthma are a huge medical problem. Despite deeper and more precise knowledge concerning their pathogenesis and the role of the immune system in these processes, so far immunotherapy is the only treatment which can modify the course of these diseases. Considering that regulatory T cells (Treg cells) have a great significance in pathogenesis of both diseases it seems appropriate to pay attention to their role in the treatment process. This work summarizes the Treg cells characteristics, the influence of allergen specific immunotherapy and other treatment modalities on Treg cells, and the possibility of using Treg cells in therapy.

Transforming growth factor beta (TGFβ) plays a crucial role in prolonging allograft survival in an allodepletion ("pruning") skin transplant model

Adoptive cell therapies involving cell manipulation to achieve tolerance are increasingly being studied in animal models and in human trials. We have demonstrated that the specific removal of allo-stimulated dividing cells (or "pruning") promotes long-term allograft survival across a major MHC mismatch in transplant models including skin, heart and islet transplants. In this study, we examine the role of transforming growth factor beta (TGFβ), an important regulatory cytokine, on allograft survival in our allodepletion or "pruning" skin transplant model. Increased proliferation of CD4(+) T cells was observed following allo-stimulation of BALB/c spleen cells (labeled with CFSE) in the presence of the regulatory cytokines TGFβ and (interleukin-2) IL-2 in a mixed lymphocyte culture (MLC). Expression of the regulatory gene forkhead box-3 (FoxP3) was increased in both the allo-stimulated non-dividing (ND) (CFSE(high)) and dividing (D) (CFSE(low)) CD4(+) T cell populations, with the highest expression found in the D CD4(+) T cell population. Mice reconstituted with allo-stimulated ND CD4(+) T cells following TGFβ/IL-2 stimulation showed prolonged allograft survival, similar to previous data. Significantly, TGFβ/IL-2 stimulation prevented acute rejection of allografts across a major MHC mismatch in the presence of highly activated allo-stimulated D CD4(+) T cells. Blockade of TGFβ promoted rejection of allografts even following depletion of allo-stimulated D CD4(+) T cells. These studies support a crucial role for TGFβ in the survival of allografts and shows that regulatory cytokines TGFβ/IL2 can delay the rejection of allografts, even in the presence of highly activated alloreactive T cells.

Alloanergization of human T cells results in expansion of alloantigen-specific CD8(+) CD28(-) suppressor cells

Allostimulation with concurrent costimulatory blockade induces alloantigen-specific hyporesponsiveness in responder T cells ("alloanergization"). Alloanergized responder cells also acquire alloantigen-specific suppressive activity, suggesting this strategy induces active immune tolerance. While this acquired suppressive activity is mediated primarily by CD4(+) FOXP3(+) cells, other cells, most notably CD8(+) suppressor cells, have also been shown to ameliorate human alloresponses. To determine whether alloanergization expands CD8(+) cells with allosuppressive phenotype and function, we used mixed lymphocyte cultures in which costimulatory blockade was provided by belatacept, an FDA-approved, second-generation CTLA-4-immunoglobulin fusion protein that blocks CD28-mediated costimulation, as an in vitro model of HLA-mismatched transplantation. This strategy resulted in an eightfold expansion of CD8(+) CD28(-) T cells which potently and specifically suppressed alloresponses of both CD4(+) and CD8(+) T cells without reducing the frequency of a range of functional pathogen-specific T cells. This CD8-mediated allosuppression primarily required cell-cell contact. In addition, we observed expansion of CD8(+) CD28(-) T cells in vivo in patients undergoing alloanergized HLA-mismatched bone marrow transplantation. Use of costimulatory blockade-mediated alloanergization to expand allospecific CD8(+) CD28(-) suppressor cells merits exploration as an approach to inducing or supporting immune tolerance to alloantigens after allogeneic transplantation.

Development of Gene Transfer for Induction of Antigen-specific Tolerance

Gene replacement therapies, like organ and cell transplantation are likely to introduce neo-antigens that elicit rejection via humoral and/or effector T cell immune responses. Nonetheless, thanks to an ever growing body of pre-clinical studies it is now well accepted that gene transfer protocols can be specifically designed and optimized for induction of antigen-specific immune tolerance. One approach is to specifically express a gene in a tissue with a tolerogenic microenvironment such as the liver or thymus. Another strategy is to transfer a particular gene into hematopoietic stem cells or immunological precursor cells thus educating the immune system to recognize the therapeutic protein as "self". In addition, expression of the therapeutic protein in pro-tolerogenic antigen presenting cells such as immature dendritic cells and B cells has proven to be promising. All three approaches have successfully prevented unwanted immune responses in pre-clinical studies aimed at the treatment of inherited protein deficiencies, e.g. lysosomal storage disorders and hemophilia, and of type I diabetes and multiple sclerosis. In this review we focus on current gene transfer protocols that induce tolerance, including gene delivery vehicles and target tissues, and discuss successes and obstacles in different disease models.

Use of gene-modified regulatory T-cells to control autoimmune and alloimmune pathology: is now the right time?

Adoptive immunotherapy using genetically targeted T-cells has recently begun to achieve impressive clinical impact in selected tumor types. Furthermore, long-term follow-up studies indicate thus far that integrating viral vectors do not elicit clinically evident genotoxicity in T-cells, unlike hematopoietic stem cells. The optimism engendered by this clinical experience provides a platform for consideration of the extended use of this technology in other disease types. One area of particular interest entails the harnessing of regulatory T-cells (Tregs) in order to down-regulate unwanted immune responses. Increasing evidence supports the efficacy of this approach in pre-clinical models of autoimmune disease and allograft rejection. Nonetheless, questions remain about optimal host cell, transgene cargo, phenotypic stability of engineered cells in vivo and potential for toxicity. Here, we review the evidence that genetically engineered Tregs can effectively dampen pathogenic immune responses and critically evaluate the prospects for clinical development of this approach.

Human regulatory T cells against minor histocompatibility antigens: ex vivo expansion for prevention of graft-versus-host disease

Alloreactive donor T cells against host minor histocompatibility antigens (mHAs) cause graft-versus-host disease (GVHD) after marrow transplantation from HLA-identical siblings. We sought to identify and expand regulatory CD4 T cells (Tregs) specific for human mHAs in numbers and potency adequate for clinical testing. Purified Tregs from normal donors were stimulated by dendritic cells (DCs) from their HLA-matched siblings in the presence of interleukin 2, interleukin 15, and rapamycin. Male-specific Treg clones against H-Y antigens DBY, UTY, or DFFRY-2 suppressed conventional CD4 T cell (Tconv) response to the specific antigen. In the blood of 16 donors, we found a 24-fold (range, 8-fold to 39-fold) excess Tconvs over Tregs reactive against sibling mHAs. We expanded mHA-specific Tregs from 4 blood samples and 4 leukaphereses by 155- to 405-fold. Cultured Tregs produced allospecific suppression, maintained demethylation of the Treg-specific Foxp3 gene promoter, Foxp3 expression, and transforming growth factor β production. The rare CD4 T conv and CD8 T cells in the end product were anergic. This is the first report of detection and expansion of potent mHA-specific Tregs from HLA-matched siblings in sufficient numbers for application in human transplant trials.

The role of regulatory T cells in the biology of graft versus host disease

Graft versus host disease (GVHD) is the major complication of allogeneic hematopoietic stem cell transplantation. GVHD is characterized by an imbalance between the effector and regulatory arms of the immune system which results in the over production of inflammatory cytokines. Moreover, there is a persistent reduction in the number of regulatory T (Treg) cells which limits the ability of the immune system to re-calibrate this proinflammatory environment. Treg cells are comprised of both natural and induced populations which have unique ontological and developmental characteristics that impact how they function within the context of immune regulation. In this review, we summarize pre-clinical data derived from experimental murine models that have examined the role of both natural and induced Treg cells in the biology of GVHD. We also review the clinical studies which have begun to employ Treg cells as a form of adoptive cellular therapy for the prevention of GVHD in human transplant recipients.

Anti-thymocyte globulin (ATG) differentially depletes naïve and memory T cells and permits memory-type regulatory T cells in nonobese diabetic mice

Background

ATG has been employed to deplete T cells in several immune-mediated conditions. However, whether ATG administration affects naïve and memory T cell differently is largely unknown.

The context and purpose of the study

In this study, we assessed how murine ATG therapy affected T cell subsets in NOD mice, based on their regulatory and naïve or memory phenotype, as well as its influence on antigen-specific immune responses.

Results

Peripheral blood CD4+ and CD8+ T cells post-ATG therapy declined to their lowest levels at day 3, while CD4+ T cells returned to normal levels more rapidly than CD8+ T cells. ATG therapy failed to eliminate antigen-primed T cells. CD4+ T cell responses post-ATG therapy skewed to T helper type 2 (Th2) and possibly IL-10-producing T regulatory type 1 (Tr1) cells. Intriguingly, Foxp3+ regulatory T cells (Tregs) were less sensitive to ATG depletion and remained at higher levels following in vivo recovery compared to controls. Of note, the frequency of Foxp3+ Tregs with memory T cell phenotype was significantly increased in ATG-treated animals.

Conclusion

ATG therapy may modulate antigen-specific immune responses through inducing memory-like regulatory T cells as well as other protective T cells such as Th2 and IL-10-producing Tr1 cells.

New ways to separate graft-versus-host disease and graft-versus-tumour effects after allogeneic haematopoietic stem cell transplantation

A major challenge to transplant immunologists and physicians remains the separation of harmful graft-versus-host disease (GvHD) and beneficial graft-versus-tumour (GvT) effects after allogeneic haematopoietic stem cell transplantation. Recent advances in our understanding of the allogeneic immune response provide potential new opportunities to achieve this goal. Three potential new approaches that capitalize on this new knowledge are considered in depth; the manipulation of organ-specific cytokines and other pro-inflammatory signals, the selective manipulation of donor effector T cell migration, and the development of cell-mediated immunosuppressive strategies using donor-derived regulatory T cells. These new approaches could provide strategies for local control of allogeneic immune responses, a new paradigm to separate GvHD and GvT effects. Although these strategies are currently in their infancy and have challenges to successful translation to clinical practice, all have exciting potential for the future.

Cell-autonomous role of TGFβ and IL-2 receptors in CD4+ and CD8+ inducible regulatory T-cell generation during GVHD

FoxP3(+) regulatory T cells (Tregs) suppress GVHD while preserving graft-versus-tumor effects, making them an attractive target for GVHD therapy. The donor-derived Treg pool can potentially be derived from the expansion of preexisting natural Tregs (nTregs) or from de novo generation of inducible Tregs (iTregs) from donor Tconvs in the transplantation recipient. Using an MHC-mismatched model of acute GVHD, in the present study we found that the Treg pool was comprised equally of donor-derived nTregs and iTregs. Experiments using various combinations of T cells from wild-type and FoxP3-deficient mice suggested that both preexisting donor nTregs and the generation of iTregs in the recipient mice contribute to protection against GVHD. Surprisingly, CD8(+)FoxP3(+) T cells represented approximately 70% of the iTreg pool. These CD8(+)FoxP3(+) T cells shared phenotypic markers with their CD4(+) counterparts and displayed suppressive activity, suggesting that they were bona fide iTregs. Both CD4(+) and CD8(+) Tregs appeared to be protective against GVHD-induced lethality and required IL-2 and TGFβ receptor expression for their generation. These data illustrate the complex makeup of the donor-derived FoxP3(+) Treg pool in allogeneic recipients and their potential role in protection against GVHD.

Improving TCR Gene Therapy for Treatment of Haematological Malignancies

Adoptive immunotherapy using TCR gene modified T cells may allow separation of beneficial Graft versus tumour responses from harmful GvHD. Improvements to this include methods to generate high avidity or high affinity TCR, improvements in vector design and reduction in mispairing. Following adoptive transfer, TCR transduced T cells must be able to survive and persist in vivo to give most effective antitumour responses. Central memory or naive T cells have both been shown to be more effective than effector cells at expanding and persisting in vivo. Lymphodepletion may enhance persistence of transferred T cell populations. TCR gene transfer can be used to redirect CD4 helper T cells, and these could be used in combination with CD8+ tumour specific T cells to provide help for the antitumour response. Antigen specific T regulatory T cells can also be generated by TCR gene transfer and could be used to suppress unwanted alloresponses.

Clinical perspectives for regulatory T cells in transplantation tolerance

Three main types of CD4+ regulatory T cells can be distinguished based upon whether they express Foxp3 and differentiate naturally in the thymus (natural Tregs) or are induced in the periphery (inducible Tregs); or whether they are FoxP3 negative but secrete IL-10 in response to antigen (Tregulatory type 1, Tr1 cells). Adoptive transfer of each cell type has proven highly effective in mouse models at preventing graft vs. host disease (GVHD) and autoimmunity. Although clinical application was initially hampered by low Treg frequency and unfavorable ex vivo expansion properties, several phase I trials are now being conducted to assess their effect on GVHD following hematopoietic stem cell transplantation (HSCT) and in type I diabetes. Human Treg trials for HSCT recipients have preceded other indications because GVHD onset is precisely known, the time period needed for prevention relatively short, initial efficacy is likely to provide life-long protection, and complications of GVHD can be lethal. This review will summarize the clinical trials conducted to date that have employed Tregs to prevent GVHD following HSCT and discuss recent advances in Treg cellular therapy.

Ex vivo expansion of human Tregs specific for alloantigens presented directly or indirectly

Adoptive transfer of regulatory T cells (Tregs) prevents GVHD in experimental animals. Because antigen activation drives Treg function, we measured the frequency, growth requirements, and function of alloantigen-specific (allospecific) Tregs from human blood. When alloantigen was presented directly, the precursor frequency of allo-specific Tregs in normal individuals was 1.02% (95% confidence interval [95% CI]: 0.65-1.59) and non-Tregs 1.56% (95% CI: 0.94-2.55). When alloantigen was presented indirectly, the frequency of specific Tregs was approximately 100-fold less. Purified Tregs were expanded with APCs, rapamycin, IL-2, and IL-15. In 12 days, allo-specific Tregs expanded 793-fold (95% CI: 480-1107), with duplication approximately every 24 hours. Purified allo-specific Tregs suppressed responses to specific alloantigen selectively and were approximately 100-fold more potent than polyspecific Tregs and nonexpanded Tregs. Allo-specific Tregs maintained high expression of Foxp3, Bcl-2, lymphoid homing receptor CD62L, and chemokine receptor CCR7, predicting sustained function and migration to lymphoid tissues in vivo. Allo-specific Tregs produced TGF-β and IL-10 and expressed more cytoplasmic CTLA-4 compared with non-Tregs. These data provide a platform for the selective expansion of Tregs against major and possibly minor histocompatibility antigens and predict the feasibility of adoptive immunotherapy trials using Tregs with indirect allo-recognition for preventing GVHD while sparing GVL effects.

Mouse models of graft-versus-host disease: advances and limitations

The limiting factor for successful hematopoietic stem cell transplantation (HSCT) is graft-versus-host disease (GvHD), a post-transplant disorder that results from immune-mediated attack of recipient tissue by donor T cells contained in the transplant. Mouse models of GvHD have provided important insights into the pathophysiology of this disease, which have helped to improve the success rate of HSCT in humans. The kinetics with which GvHD develops distinguishes acute from chronic GvHD, and it is clear from studies of mouse models of GvHD (and studies of human HSCT) that the pathophysiology of these two forms is also distinct. Mouse models also further the basic understanding of the immunological responses involved in GvHD pathology, such as antigen recognition and presentation, the involvement of the thymus and immune reconstitution after transplantation. In this Perspective, we provide an overview of currently available mouse models of acute and chronic GvHD, highlighting their benefits and limitations, and discuss research and clinical opportunities for the future.

Mechanism of immune hyporesponsiveness induced by recipient- derived immature dendritic cells in liver transplantation rat

OBJECTIVE

To investigate the mechanism of immune hyporesponsiveness induced by donor-antigen- unloaded recipient-derived immature dendritic cell (imDC) of liver grafts in rats.

METHODS

Forty Sprague-Dawley rats (donor) and forty male Wistar rats (recipient) were randomly divided into 4 groups: control, cyclosporine A (CsA), mature DC (mDC), and imDC groups respectively, with 10 donor rats and 10 recipient rats in each group. Recipient rats in CsA group were treated with 10 mg•kg⁻¹•d⁻¹ CsA starting day 2 after the transplantation. Recipients in the mDC or imDC groups were given Wistar rat derived mDCs (1 × 10⁶/rat) or imDCs (1 × 10⁶/rat) via dorsal vein of the penis respectively 1 day before the transplantation. In each group, 5 recipients were kept for determination of survival time and the other 5 rats were executed at day 10 after transplantation. Blood samples were collected for the measurement of serum alanine aminotransferase (ALT), total bilirubin (TBIL), interleukin 2 (IL-2), interferon gamma (IFN-γ), IL-4, and IL-10 levels. Liver tissue was harvested for HE staining and acute rejection evaluation. Expression levels of Fas-L/Fas in the grafts were detected by immunohistochemical staining; and Western blot was used to detect the expression level of Scurfin.

RESULTS

The survival time of CsA and imDC groups was significantly longer than that of control and mDC groups (all P < 0.05). The levels of serum ALT and TBIL in the control group (2072.20 ± 217.93 IU/L and 147.42 ± 22.02 µmol/L) and mDC group (2117.00 ± 285.13 IU/L and 141.58 ± 20.82 µmol/L) were significantly higher than those in the CsA group (59.68 ± 13.48 IU/L and 15.40 ± 2.13 µmol/L) or imDC group (50.80 ± 9.63 IU/L and 14.44 ± 3.49 µmol/L) (all P < 0.05). In the CsA and imDC groups, the levels of IL-2 (22.52 ± 3.75 pg/mL and 22.12 ± 3.90 pg/mL) and IFN-γ (309.20 ± 25.19 pg/mL and 321.00 ± 21.64 pg/mL) were significantly lower, but the levels of IL-4 (297.60 ± 25.07 pg/mL and 277.00 ± 22.47 pg/mL) and IL-10 (1226.00 ± 140.49 pg/mL and 1423.00 ± 106.39 pg/mL) were higher than those of the control (IL-2: 147.78 ± 12.80 pg/mL, IFN-γ: 1758.60 ± 106.22 pg/mL, IL-4: 17.40 ± 4.77 pg/mL, IL-10: 81.00 ± 9.47 pg/mL) and mDC groups (IL-2: 142.34 ± 9.29 pg/mL, IFN-γ: 1835.00 ± 82.63 pg/mL, IL-4: 15.60 ± 3.96 pg/mL, IL-10: 68.80 ± 11.23 pg/mL) (all P < 0.01). The expression level of Scurfin protein on CD4+ CD25+ T cells of the imDC group (1.34 ± 0.29) was significantly higher than that in the control (0.72 ± 0.13), CsA (0.37 ± 0.11), and mDC groups (0.78 ± 0.17) (all P < 0.05).

CONCLUSION

Donor-antigen-unloaded recipient-derived imDC is an effective treatment in inducing immune hyporesponsiveness through induction of T cell apoptosis, shift in Thl/Th2 balance, and proliferation of regulatory T cell.

Abrogation of Treg function deteriorates rheumatoid arthritis

An early prognostic indicator which warns of progressive joint destruction of rheumatoid arthritis (RA) was explored using a novel suspension-array technique in moderate (Steinbrocker stage I and II) and severe (Steinbrocker stage IV) RA patients. DNA microarray analysis of peripheral blood lymphocytes showed significant increase of interleukin (IL)-2 receptor α-chain (CD25) gene expression, a regulatory T cell (Treg) surface marker in severe RA patients. In contrast, suspension array, a comprehensive bead-based enzyme-linked immunosorbent assay (ELISA), revealed decreased production of IL-10 and increased production of interferon (IFN)-γ in sera in the incipient stage of the aggressive disease process. Both in moderate and in severe RA patients, the IFN-γ/IL-10 ratio indicated deterioration of the disease with universal validity. Fluorescence-activated cell sorting (FACS) and reverse-transcription polymerase chain reaction (RT-PCR) analysis showed extant CD4+CD25+ regulatory T cells in severe RA patients, however Foxp3, a regulatory T cell-specific transcription factor, gene expression was absent, while glucocorticoid-induced tumor necrosis factor (TNF) receptor family-related protein (GITR), which transmits a signal that abrogates regulatory T cell functions, was elevated. In the current study, we showed the validity of suspension-array analysis for enabling more complete understanding of RA, and showed that IFN-γ/IL-10 ratio can be a prognostic tool for early lesion and more aggressive RA.

Autoimmune hepatitis

Autoimmune hepatitis (AIH) is an inflammatory liver disease that mainly affects females. It is characterized histologically by interface hepatitis, biochemically by increased aspartate and alanine aminotransferase levels, and serologically by the presence of autoantibodies and increased levels of immunoglobulin G. AIH affects both adults and children, and is particularly aggressive in the latter group. It is a relatively rare but devastating disease, which progresses rapidly unless immunosuppressive treatment is started promptly. With appropriate treatment 80% of patients achieve remission and long-term survival. Those patients who progress to end-stage liver disease because they are unresponsive or nonadherent to treatment, and those with fulminant liver failure (encephalopathy grade II-IV) at diagnosis, require liver transplantation. Seropositivity for smooth muscle and/or antinuclear antibodies defines type 1 AIH, while positivity for liver kidney microsomal type 1 antibodies defines type 2 AIH. The primary cause of AIH is unknown; however, considerable knowledge about the mechanisms of liver damage involved has been gathered over the past 30 years, which is likely to provide the basis for specific modes of treatment and a possible cure.

Immunotherapy with regulatory T cells in transplantation

Regulatory T cell (Treg)-based immunotherapy is of great interest to induce tolerance in clinical transplantation settings. In fact, the first clinical trials of Treg infusion after stem cell transplantation have recently begun. However, many important issues regarding human Treg immunotherapy are still to be resolved. In this review, we provide a short update on Tregs and elaborate on various strategies for Treg-based immunotherapy. First, infusion of ex vivo-selected naturally occurring Tregs is addressed, with emphasis on Treg isolation, expansion, antigen specificity, homing and stability. Next, the potential of ex vivo-induced Treg transfusion strategies is discussed. Finally, therapies aimed at in vivo increase of Treg numbers or function are addressed. In addition, we summarize the current knowledge on effects of immunosuppressive drugs on Tregs. In the following years, we expect exciting new data regarding the clinical application of Treg immunotherapy in transplantation to be released.

Host APCs augment in vivo expansion of donor natural regulatory T cells via B7H1/B7.1 in allogeneic recipients

Foxp3(+) regulatory T (Treg) cells include thymic-derived natural Treg and conventional T-derived adaptive Treg cells. Both are proposed to play important roles in downregulating inflammatory immune responses. However, the mechanisms of Treg expansion in inflammatory environments remain unclear. In this study, we report that, in an autoimmune-like graft-versus-host disease model of DBA/2 (H-2(d)) donor to BALB/c (H-2(d)) recipients, donor Treg cells in the recipients predominantly originated from expansion of natural Treg cells and few originated from adaptive Treg cells. In vivo neutralization of IFN-γ resulted in a marked reduction of donor natural Treg expansion and exacerbation of graft-versus-host disease, which was associated with downregulation of host APC expression of B7H1. Furthermore, host APC expression of B7H1 was shown to augment donor Treg survival and expansion. Finally, donor Treg interactions with host APCs via B7.1/B7H1 but not PD-1/B7H1 were demonstrated to be critical in augmenting donor Treg survival and expansion. These studies have revealed a new immune regulation loop consisting of T cell-derived IFN-γ, B7H1 expression by APCs, and B7.1 expression by Treg cells.

Efficient and selective prevention of GVHD by antigen-specific induced Tregs via linked-suppression in mice

Naturally occurring regulatory T cells (nTregs) suppress the development of graft-versus-host disease (GVHD) and may spare graft-versus-leukemia (GVL) effect. Because nTreg is a rare population in a healthy individual, the limited source and the non-selective suppression are major hurdles towards the application of nTregs in the control of clinical GVHD after allogeneic hematopoietic cell transplantation (HCT). An alternative approach is to generate induced Tregs (iTregs) from naïve CD4 precursors, but the effectiveness of iTregs in the control of GVHD is highly controversial and requires further investigation. The other critical but unsolved issue in Treg therapy is how to achieve antigen (Ag)-specific tolerance that distinguishes GVHD and GVL effects. To address the important issues on the effectiveness of iTregs and Ag-specificity of Tregs, we generated Ag-specific iTregs and tested their potential in the prevention of GVHD in a pre-clinical bone marrow transplantation (BMT) model. CD4(+)CD25(+)Foxp3(+) iTregs generated from OT-II TCR transgenic T cells specific for OVA target Ag efficiently prevented GVHD induced by polyclonal T effector cells (Teffs) only in the allogeneic recipients that express OVA protein but not in OVA(-) recipients. The efficacy of these Ag-specific iTregs was significantly higher than polyclonal iTregs. As controls, OT-II CD4(+)Foxp3(-) cells had no effect on GVHD development in OVA(-) recipients and exacerbated GVHD in OVA(+) recipients when transplanted together with polyclonal Teffs. Because the iTregs recognize OVA whereas Teffs recognize alloAg bm12, our data reveal for the first time, to our knowledge, that Tregs prevent GVHD through a linked suppression. Mechanistically, OT-II iTregs expanded extensively, and significantly suppressed expansion and infiltration of Teffs in OVA(+) but not in OVA(-) recipients. These results demonstrate that Ag-specific iTregs can prevent GVHD efficiently and selectively, providing a proof of principle that Ag-specific iTregs may represent a promising cell therapy for their specificity and higher efficacy in allogeneic HCT.

Platelet-lysate-expanded mesenchymal stromal cells as a salvage therapy for severe resistant graft-versus-host disease in a pediatric population

Despite advances in graft-versus-host-disease (GVHD) treatment, it is estimated that overall survival (OS) at 2 years for hematopoietic cell transplantation (HCT) recipients who experience steroid-resistant GVHD is 10%. Among recent therapeutic approaches for GVHD treatment, mesenchymal stromal cells (MSCs) hold a key position. We describe a multicenter experience of 11 pediatric patients diagnosed with acute or chronic GVHD (aGVHD, cGVHD) treated for compassionate use with GMP-grade unrelated HLA-disparate donors' bone marrow-derived MSCs, expanded in platelet-lysate (PL)-containing medium. Eleven patients (aged 4-15 years) received intravenous (i.v.) MSCs for aGVHD or cGVHD, which was resistant to multiple lines of immunosuppression. The median dose was 1.2 x 10(6)/kg (range: 0.7-3.7 x 10(6)/kg). No acute side effects were observed, and no late side effects were reported at a median follow-up of 8 months (range: 4-18 months). Overall response was obtained in 71.4% of patients, with complete response in 23.8% of cases. None of our patients presented GVHD progression upon MSC administration, but 4 patients presented GVHD recurrence 2 to 5 months after infusion. Two patients developed chronic limited GVHD. This study underlines the safety of PL-expanded MSC use in children. MSC efficacy seems to be greater in aGVHD than in cGVHD, even after failure of multiple lines of immunosuppression.

Can antigen-specific regulatory T cells protect against graft versus host disease and spare anti-malignancy alloresponse?

Allogeneic hematopoietic cell transplantation provides effective control of hematopoietic malignancies, but with an associated risk of graft-versus-host disease (GVHD) related morbidity and mortality. Several advances in hematopoietic cell transplantation including high resolution HLA typing, development of reduced intensity conditioning regimens, infectious prophylaxis and treatment, and novel immunosuppressive agents have resulted in improved outcomes and improved access to transplantation, but GVHD remains a major obstacle. This clinico-pathological syndrome, mediated by donor alloreactive T cells, occurs often despite prophylactic immunosuppressive therapy. Regulatory T cells, a suppressive subset of the T-cell repertoire, may offer promise as a novel cellular therapy for more effective prevention of GVHD. While advances have been made in pre-clinical experimental animals, several challenges remain in the translation of this work to human trials. Strategies to effectively produce ex vivo expanded alloantigen-specific regulatory T cells specific for ubiquitous alloantigens but sparing hematopoietic- or tumor-associated antigens hold promise to prevent GVHD while allowing a preserved graft versus malignancy effect.

The effect of rabbit anti-thymocyte globulin induction therapy on regulatory T cells in kidney transplant patients

BACKGROUND

Prevention of alloreactivity by rabbit anti-thymocyte globulins (rATG) may not only result from immunodepletion but also from the induction of T cells that control allogeneic immune responses. In the present prospective and controlled study, we investigated the effect of rATG on the frequency, function and phenotype of peripheral immunoregulatory CD4+ T cells in kidney transplant (KTx) patients.

METHODS

After transplantation, 16 patients received ATG-induction therapy and triple therapy consisting of tacrolimus, MMF and steroids. The control group (n = 18) received triple therapy only. By flow cytometry, T cells were analysed for CD25, FoxP3, CD127, CD45RO and CCR7. To study their suppressive capacities, CD25bright T cells were co-cultured with CD25(-/dim) effector T cells (Teff) in mixed lymphocyte reactions (MLR), stimulated with donor and third party (3P) antigens.

RESULTS

Pre-transplant levels of FoxP3+CD127(-/low) T cells were 6% of CD4+ T cells. One week post-ATG treatment, no measurable numbers of regulatory T cells were present (P < 0.01). After 4 weeks, the cell numbers of CD4+FoxP3+CD127(-/low) T cells slowly reappeared and thereafter remained low (P < 0.01). At 14 weeks, a significant shift towards the CD45RO+CCR7+ (central memory) phenotype within CD4+FoxP3+ T cells was observed (P < 0.01). At 26 weeks, the proliferative alloresponses of the PBMC and CD25(-/dim) Teff profoundly decreased compared to pre-transplant (P = 0.01 and P = 0.02 respectively), while the regulatory capacity of the CD25bright T cells, of which 90% consisted of FoxP3+CD127(-/low) T cells, remained unaffected. The CD25bright T cells suppressed the anti-donor (94%) and 3P responses (93%).

CONCLUSION

Our findings show that rATG therapy does not spare peripheral immunoregulatory T cells in vivo, but after regeneration preserves their suppressive activity.

Using histone deacetylase inhibitors to enhance Foxp3(+) regulatory T-cell function and induce allograft tolerance

The histone/protein deacetylase inhibitor (HDACi), trichostatin A (TsA), increases the production and suppressive function of Foxp3(+) regulatory T cells (T(regs)), at least in part, by promoting the acetylation of Foxp3 protein itself. Acetylation of Foxp3 is required for effective binding of Foxp3 to the promoter of the interleukin-2 (IL-2) gene and the suppression of IL-2 expression. We have sought to identify agents that had similar effects on T(regs), but without the associated toxicity of TsA. This review summarizes the contrasting effects of various HDACis on T(reg) functions in vitro and in vivo. Agents that block primarily class I HDAC had minimal or no effect on T(reg) suppression, whereas multiple inhibitors of both class I and class II HDAC enhanced T(reg) suppression in vitro and in vivo. These data indicate tools for further analysis of T(reg) functions, and point to a critical role of class II HDAC in the regulation of T(regs). Such knowledge has direct implications for the development of in vivo approaches to treat autoimmune and other inflammatory diseases.

Ethylenecarbodiimide-coupled allogeneic antigen presenting cells induce human CD4+ regulatory T cells

Adoptive transfer of naturally occurring CD4(+)CD25(+) regulatory T cells can tolerize transplantation alloresponses in animal models. However isolation of these cells in sufficient numbers from humans is cumbersome and prone to contamination with alloreactive CD25(+) T cells. Incubation of ethylenecarbodiimide-coupled antigen presenting cells (APC) with naïve T cells and antigen has been shown to induce tolerance in various experimental models. We therefore investigated whether ECDI-coupled allogeneic APC were able to induce an expandable human CD4(+) Treg population. CD4(+) and CD4(+) CD25(-) cells cultured for 5 days with ECDI-treated human PBMC exhibited potent suppressive capacity in a mixed lymphocyte reaction. Induction of these ECDI-Tregs was associated with up-regulation of Foxp3 mRNA and protein expression and they maintained high expression of CD62L and CD27 as well as low CD127 expression. ECDI-treated APC displayed reduced expression of the co-stimulatory signaling molecules CD40 and CD80, and failed to stimulate proliferation and cytokine secretion in co-cultured CD4(+) T cells. Restimulation in the presence of rapamycin and hrIL-2 led to expansion of ECDI-Tregs with increasing Foxp3 levels and suppressive activity significantly higher than expanded naturally occurring CD4(+)CD25(+) Tregs. In summary these findings support the hypothesis that ECDI-coupled APC can convert naïve CD4(+) T cells into functional Tregs with different phenotypic characteristics than naturally occurring CD4(+)CD25(+) Tregs. These inducible Tregs could provide a novel approach that might facilitate the translation of ex vivo generated and expanded Tregs into clinical settings.

Forced overexpression of either of the two common human Foxp3 isoforms can induce regulatory T cells from CD4(+)CD25(-) cells

The forkhead/winged helix transcription factor (Foxp3) is expressed as two different isoforms in humans: the full-length isoform (Foxp3FL) and an alternative-splicing product lacking the exon 2 (Foxp3DeltaE2). We here studied the cellular distribution of Foxp3 isoforms by quantitative PCR and evaluated the functional outcome of retroviral transduction of Foxp3FL and Foxp3DeltaE2 genes into CD4(+)CD25(-) cells. In PBMC, both isoforms were preferentially expressed in CD4(+)CD25(hi) cells. In single-cell-sorted and expanded Treg, both Foxp3 isoforms were expressed simultaneously but without a fixed ratio. Forced expression of Foxp3FL or Foxp3DeltaE2 genes in CD4(+)CD25(-) T cells induced bona fide Treg that not only displayed Treg phenotype but also were anergic and mediated significant suppressive activity against CD3-activated CD4(+)CD25(-) cells. GFP(-) nontransduced cells or cells transduced with an empty vector showed no Treg phenotype, anergy or suppressive activities. In conclusion, our results reveal that both Foxp3 isoforms possess similar capacities to induce Treg; however, unnaturally high expression levels are required to convey Treg functions to CD4(+)CD25(-) cells. As both Foxp3 isoforms appear to be expressed in an independent fashion, studies aiming at quantification of Treg in peripheral blood or in tissue samples can benefit from determination of total Foxp3 levels rather than one of the isoforms.

Provision of antifungal immunity and concomitant alloantigen tolerization by conditioned dendritic cells in experimental hematopoietic transplantation

FoxP3(+) regulatory T (Treg) cells are important mediators of peripheral tolerance, and deficiency of this population is associated with autoimmune inflammation and onset of acute lethal graft-vs.-host disease in transplantation. Type I IFN-producing plasmacytoid dendritic cells (pDC) are implicated in the induction and maintenance of tolerance and contribute to engraftment facilitation and prevention of graft-vs.-host disease after allogeneic hematopoietic stem cells transplantation (HSCT). Because host DC function is impaired during the immediate period post-transplant, the administration of donor DC may be useful for the educational program of recovering T cells. Distinct DC subsets could be derived from bone marrow (murine) or peripheral CD14(+) cell (human) cultures in the presence of either GM-CSF/IL-4 (myeloid DC) or FLT3-ligand (mainly pDC). The ability of either DC subset to induce Th1/Treg cell priming against Aspergillus fumigatus as well as the relative contribution of murine DC subsets to antifungal priming upon adoptive transfer in hematopoietic transplanted mice with aspergillosis is not known. We found specialization and complementarity in priming and tolerization by the different DC subsets, with FL-DC fulfilling the requirement for (i) Th1/Treg antifungal priming; ii) tolerization toward alloantigens and (iii) diversion from alloantigen-specific to antigen-specific T cell responses in the presence of donor T lymphocytes. Interestingly, thymosin alpha1 (Talpha1), known to modulate human pDC functions trough TLR9, affects mobilization and tolerization of pDC by activating the indoleamine 2,3-dioxygenase-dependent pathway, and this resulted in Treg development and tolerization. Thus, transplantation tolerance and concomitant pathogen clearance could be achieved through the therapeutic induction of antigen-specific Treg cells via instructive immunotherapy with pathogen- or TLR-conditioned donor DC.

Hyperexpression of Foxp3 and IDO During Acute Rejection of Islet Allografts

BACKGROUND

We investigated the hypothesis that Foxp3+ cells are an integral component of antiallograft immunity but are dominated by pathogenic effectors.

METHODS

Wild-type H-2b C57BL/6 (B6) mice or B6 mice with a targeted disruption of c-Rel gene (c-Rel-/-) were used as recipients of islet grafts from allogeneic DBA/2 (H-2d) mice or syngeneic B6 mice. We developed kinetic quantitative polymerase chain reaction assays and measured intragraft expression of mRNA for Foxp3, IDO, cytolytic molecules, proinflammatory cytokines, and chemokines/receptors.

RESULTS

Intraislet levels of mRNA for Foxp3, IDO, CD3, CD25, tumor necrosis factor-alpha, RANTES, IP-10, and CXCR3 were highest in DBA/2 islet allografts from WT B6 recipients compared to DBA/2 islet allografts from c-Rel-/- B6 recipients or syngeneic B6 islet grafts from WT B6 mice. The ratio of granzyme B or IFN-gamma to Foxp3 was higher with the DBA/2 islet allografts from the WT B6 recipients compared to DBA/2 islet allografts from c-Rel-/- B6 recipients or B6 islet grafts from WT B6 recipients.

CONCLUSIONS

Foxp3+ cells are an integral component of acute rejection of allografts but may be dominated by pathogenic effectors.

Foxp3-expressing CD4(+)T cells under the control of INF-gamma promoter prevent diabetes in NOD mice

Foxp3-transduced CD4(+)T-cells have been used for treating autoimmune diseases such as type I diabetes. However, while suppressing the activity of pathogenic T cells, they could suppress the activity of bystander T cells as well. Therefore more specific strategies need to be developed. We designed and tested a new strategy that involves converting pathogenic CD4(+)Th1 cells into regulatory T-cells by lentiviral transduction with Foxp3 under the control of interferon-gamma (IFN-gamma) promoter (IgammaP-Foxp3). After transduction under the IgammaP control, Foxp3 expression in diabetic CD4(+)Th1 cells was favored. IgammaP-Foxp3-transduced CD4(+)T cells were anergic in vitro to stimulation by antigen. The process of IgammaP-Foxp3-transduced CD4(+)T cells differentiating into Treg cells and Treg cells losing their phenotype and functions has the effect of significantly suppressing incidence and onset of diabetes and autoantigen-specific T cell response, while increasing/maintaining endogenous Tregs in nonobese diabetic (NOD) mice recipients. In this manner, CD4(+)T cells of greater specificity were developed by transducing pathogenic CD4(+)Th1 cells with Foxp3 under the control of IgammaP, in order to prevent diabetes in NOD mice. The findings of this study provide a basis for more reasonable regulatory T cells (Tregs)-based therapy, with autoimmunity being suppressed through indirect means known as "infectious tolerance".