Adoptive Transfer Of Treg Cells Research Articles

Adoptive Transfer of Treg Cells Combined with Mesenchymal Stem Cells Facilitates Repopulation of Endogenous Treg Cells in a Murine Acute GVHD Model.

Therapeutic effects of combined cell therapy with mesenchymal stem cells (MSCs) and regulatory T cells (Treg cells) have recently been studied in acute graft-versus-host-disease (aGVHD) models. However, the underlying, seemingly synergistic mechanism behind combined cell therapy has not been determined. We investigated the origin of Foxp3+ Treg cells and interleukin 17 (IL-17+) cells in recipients following allogeneic bone marrow transplantation (allo-BMT) to identify the immunological effects of combined cell therapy. Treg cells were generated from eGFP-expressing C57BL/6 mice (Tregegfp cells) to distinguish the transferred Treg cells; recipients were then examined at different time points after BMT. Systemic infusion of MSCs and Treg cells improved survival and GVHD scores, effectively downregulating pro-inflammatory Th×and Th17 cells. These therapeutic effects of combined cell therapy resulted in an increased Foxp3+ Treg cell population. Compared to single cell therapy, adoptively transferred Tregegfp cells only showed prolonged survival in the combined cell therapy group on day 21 after allogeneic BMT. In addition, Foxp3+ Treg cells, generated endogenously from recipients, significantly increased. Significantly higher levels of Tregegfp cells were also detected in aGVHD target organs in the combined cell therapy group compared to the Treg cells group. Thus, our data indicate that MSCs may induce the long-term survival of transferred Treg cells, particularly in aGVHD target organs, and may increase the repopulation of endogenous Treg cells in recipients after BMT. Together, these results support the potential of combined cell therapy using MSCs and Treg cells for preventing aGVHD.

FOXP3 is a promising and potential candidate gene in generalised vitiligo susceptibility.

FOXP3 is a promising and potential candidate gene in generalised vitiligo susceptibility.

Large-scale Isolation of Highly Pure "Untouched" Regulatory T Cells in a GMP Environment for Adoptive Cell Therapy.

Adoptive cell therapy is an emerging treatment strategy for a number of serious diseases. Regulatory T (Treg) cells represent 1 cell type of particular interest for therapy of inflammatory conditions, as they are responsible for controlling unwanted immune responses. Initial clinical trials of adoptive transfer of Treg cells in patients with graft-versus-host disease were shown to be safe. However, obtaining sufficient numbers of highly pure and functional Treg cells with minimal contamination remains a challenge. We developed a novel approach to isolate "untouched" human Treg cells from healthy donors on the basis of negative selection using the surface markers CD49d and CD127. This procedure, which uses an antibody cocktail and magnetic beads for separation in an automated system (RoboSep), was scaled up and adapted to be compatible with good manufacturing practice conditions. With this setup we performed 9 Treg isolations from large-scale leukapheresis samples in a good manufacturing practice facility. These runs yielded sufficient numbers of "untouched" Treg cells for immediate use in clinical applications. The cell preparations consisted of viable highly pure FoxP3-positive Treg cells that were functional in suppressing the proliferation of effector T cells. Contamination with CD4 effector T cells was <10%. All other cell types did not exceed 2% in the final product. Remaining isolation reagents were reduced to levels that are considered safe. Treg cells isolated with this procedure will be used in a phase I clinical trial of adoptive transfer into leukemia patients developing graft-versus-host disease after stem cell transplantation.

Regulatory T cells ameliorate acetaminophen-induced immune-mediated liver injury (IRC11P.439)

Abstract The contribution of innate immune cells to acetaminophen (APAP)-induced liver injury has been extensively investigated. However, the roles of T cell populations among adaptive immune cells in APAP-induced liver injury remain to be elucidated. Herein, we found that distinct CD4+ T cell subsets but not CD8+ T cells modulated APAP-induced liver injury in mice. After APAP challenge, more CD62LlowCD44hiCD4+ T cells appeared in the liver, accompanied by increased IFN-γ. The removal of CD4+ T cells by either antibody depletion or genetic deficiency markedly compromised pro-inflammatory cytokine levels and ameliorated liver injury. Meanwhile, we also found that the frequency and absolute number of Treg cells also increased. Treg cell depletion increased hepatic CD62LlowCD44hiCD4+ T cells, augmented pro-inflammatory cytokines, and exacerbated liver injury, while adoptive transfer of Treg cells ameliorated APAP-induced liver injury. Our investigation suggests that Th1 and Treg subsets are involved in regulating APAP-induced liver injury. Thus, modulating the Th1/Treg balance may be an effective strategy to prevent and/or treat APAP-induced liver injury.

Regulatory T cells ameliorate acetaminophen-induced immune-mediated liver injury.

The contribution of innate immune cells to acetaminophen (APAP)-induced liver injury has been extensively investigated. However, the roles of T cell populations among adaptive immune cells in APAP-induced liver injury remain to be elucidated. Herein, we found that distinct CD4(+) T cell subsets but not CD8(+) T cells modulated APAP-induced liver injury in mice. After APAP challenge, more CD62L(low)CD44(hi)CD4(+) T cells appeared in the liver, accompanied by increased IFN-γ. The removal of CD4(+) T cells by either antibody depletion or genetic deficiency markedly compromised pro-inflammatory cytokine levels and ameliorated liver injury. Meanwhile, we also found that the frequency and absolute number of Treg cells also increased. Treg cell depletion increased hepatic CD62L(low)CD44(hi)CD4(+) T cells, augmented pro-inflammatory cytokines, and exacerbated liver injury, while adoptive transfer of Treg cells ameliorated APAP-induced liver injury. Furthermore, the recruitment of Treg cells into the liver through specific expression of CXCL10 in the liver could ameliorate APAP-induced liver injury. Our investigation suggests that Th1 and Treg subsets are involved in regulating APAP-induced liver injury. Thus, modulating the Th1/Treg balance may be an effective strategy to prevent and/or treat APAP-induced liver injury.

Regulatory T cells modulate inflammation and reduce infarct volume in experimental brain ischaemia.

Brain ischaemia (stroke) triggers an intense inflammatory response predominately mediated by the accumulation of inflammatory cells and mediators in the ischaemic brain. In this context, regulatory T (Treg) cells, a subpopulation of CD4+ T cells with immunosuppressive and anti-inflammatory properties, are activated in the late stages of the disease. To date, the potential therapeutic usefulness of Treg cells has not been tested. In this study, we aimed to investigate whether Treg cells exert protection/repair following stroke. Both the adoptive transfer of Treg cells into ischaemic rats and the stimulation of endogenous T-cell proliferation using a CD28 superagonist reduced the infarct size at 3–28 days following the ischaemic insult. Moreover, T cell-treated animals had higher levels of FoxP3 and lower levels of IL-1β, CD11b+ and CD68+ cells in the infarcted hemisphere when compared with control animals. However, T-cell treatment did not alter the rate of proliferation of NeuN-, NCAM- or CD31-positive cells, thereby ruling out neurogenesis and angiogenesis in protection. These results suggest that adoptive transfer of T cells is a promising therapeutic strategy against the neurological consequences of stroke.

Lung microbiota promotes tolerance to allergens in neonates via PD-L1.

Epidemiological data point toward a critical period in early life during which environmental cues can set an individual on a trajectory toward respiratory health or disease. The neonatal immune system matures during this period, although little is known about the signals that lead to its maturation. Here we report that the formation of the lung microbiota is a key parameter in this process. Immediately following birth, neonatal mice were prone to develop exaggerated airway eosinophilia, release type 2 helper T cell cytokines and exhibit airway hyper-responsiveness following exposure to house dust mite allergens, even though their lungs harbored high numbers of natural CD4(+)Foxp3(+)CD25(+)Helios(+) regulatory T (Treg) cells. During the first 2 weeks after birth, the bacterial load in the lungs increased, and representation of the bacterial phyla shifts from a predominance of Gammaproteobacteria and Firmicutes towards Bacteroidetes. The changes in the microbiota were associated with decreased aeroallergen responsiveness and the emergence of a Helios(-) Treg cell subset that required interaction with programmed death ligand 1 (PD-L1) for development. Absence of microbial colonization(10) or blockade of PD-L1 during the first 2 weeks postpartum maintained exaggerated responsiveness to allergens through to adulthood. Adoptive transfer of Treg cells from adult mice to neonates before aeroallergen exposure ameliorated disease. Thus, formation of the airway microbiota induces regulatory cells early in life, which, when dysregulated, can lead to sustained susceptibility to allergic airway inflammation in adulthood.

Adoptive transfer of Treg cells counters adverse effects of Toxoplasma gondii infection on pregnancy.

Acute infection with Toxoplasma gondii (T. gondii) during pregnancy is associated with adverse outcomes. The mechanisms that cause this phenomenon are not clear. Regulatory T cells (Tregs) are involved in maternal tolerance, and here we observed a decrease in the absolute numbers of CTLA-4(+) Tregs and PD-1(+) Tregs in spleen and at the fetal-maternal interface in T. gondii-infected mice. Our results suggest that T. gondii induces apoptosis of Tregs. Additionally, we found that the expression of CTLA-4 and PD-1 on Tregs at fetal-maternal interface were higher than on spleen cells from normal pregnant mice. Therefore, we adoptively transferred Tregs from fetal-maternal interface or from spleens of normal pregnant mice into infected pregnant mice. Pregnancy outcomes were improved when Tregs were transferred from the fetal-maternal interface but not from the spleen. The mechanism appears to be through up-regulation of the number of CTLA-4(+) Tregs and PD-1(+) Tregs and correction of the imbalance between tolerant cytokines (IL-10, TGF-β) and inflammatory cytokines (IFN-γ). Our data indicate that Tregs at fetal-maternal interface express high levels of inhibitory molecules that play a vital immuno-protective role during pregnancy.

Adoptive transfer of Treg cells to B6 mice during Toxoplasma gondii infection induces down-modulation of exacerbated inflammatory immune response but does not generate protection (MPF1P.777)

Abstract Toxoplasmosis is an infection disease affecting one third of the world population and is caused by the protozoan parasite Toxoplasma gondii. TH1 immune response is necessary for protection, IFN-γ being the major mediator of resistance. An exacerbated TH1 immune response however, is detrimental. Regulatory T (Treg) are CD4+Foxp3+ cells that actively suppress pathological and physiological immune responses, thereby contributing to the maintenance of immune homeostasis. It has been reported that during acute toxoplasmosis in B6 mice, Treg cell number decreases. In order to analyze if Treg cells are involved in protection during T. gondii infection, we carried out adoptive transfer of Treg cells to infected mice. We observed a decreased mortality when Treg cells were adoptively transferred but an increased number of cysts in brain was detected. A decreased pathology in the small intestine, a decreased production of IFN-γ and TNF-α in serum, a decreased activation in CD4+ cells, and a decreased production of IFN-γ by CD4+ cells was also observed in the same mice. All these results suggest that adoptive transfer of Treg cells during T. gondii infection down-modulate the exacerbated immune response, but it does not generate protection in B6 mice. Thus Treg cells are not involved in protection during T. gondii infection.

Induction of Regulatory T Cells by High-Dose gp96 Suppresses Murine Liver Immune Hyperactivation

Immunization with high-dose heat shock protein gp96, an endoplasmic reticulum counterpart of the Hsp90 family, significantly enhances regulatory T cell (Treg) frequency and suppressive function. Here, we examined the potential role and mechanism of gp96 in regulating immune-mediated hepatic injury in mice. High-dose gp96 immunization elicited rapid and long-lasting protection of mice against concanavalin A (Con A)-and anti-CD137-induced liver injury, as evidenced by decreased alanine aminotransaminase (ALT) levels, hepatic necrosis, serum pro-inflammatory cytokines (IFN-γ, TNF-α, and IL-6), and number of IFN-γ + CD4+ and IFN-γ + CD8+ T cells in the spleen and liver. In contrast, CD4+CD25+Foxp3+ Treg frequency and suppressive function were both increased, and the protective effect of gp96 could be generated by adoptive transfer of Treg cells from gp96-immunized mice. In vitro co-culture experiments demonstrated that gp96 stimulation enhanced Treg proliferation and suppressive function, and up-regulation of Foxp3, IL-10, and TGF-β1 induced by gp96 was dependent on TLR2- and TLR4-mediated NF-κB activation. Our work shows that activation of Tregs by high-dose gp96 immunization protects against Con A- and anti-CD137-induced T cell-hepatitis and provides therapeutic potential for the development of a gp96-based anti-immune hyperactivation vaccine against immune-mediated liver destruction.

Chloroquine Treatment Enhances Regulatory T Cells and Reduces the Severity of Experimental Autoimmune Encephalomyelitis

BackgroundThe modulation of inflammatory processes is a necessary step, mostly orchestrated by regulatory T (Treg) cells and suppressive Dendritic Cells (DCs), to prevent the development of deleterious responses and autoimmune diseases. Therapies that focused on adoptive transfer of Treg cells or their expansion in vivo achieved great success in controlling inflammation in several experimental models. Chloroquine (CQ), an anti-malarial drug, was shown to reduce inflammation, although the mechanisms are still obscure. In this context, we aimed to access whether chloroquine treatment alters the frequency of Treg cells and DCs in normal mice. In addition, the effects of the prophylactic and therapeutic treatment with CQ on Experimental Autoimmune Encephalomyelitis (EAE), an experimental model for human Multiple Sclerosis, was investigated as well.Methodology/Principal FindingsEAE was induced in C57BL/6 mice by immunization with myelin oligodendrocyte glycoprotein (MOG35–55) peptide. C57BL/6 mice were intraperitoneally treated with chloroquine. Results show that the CQ treatment provoked an increase in Treg cells frequency as well as a decrease in DCs. We next evaluated whether prophylactic CQ administration is capable of reducing the clinical and histopathological signs of EAE. Our results demonstrated that CQ-treated mice developed mild EAE compared to controls that was associated with lower infiltration of inflammatory cells in the central nervous system CNS) and increased frequency of Treg cells. Also, proliferation of MOG35–55-reactive T cells was significantly inhibited by chloroquine treatment. Similar results were observed when chloroquine was administrated after disease onset.ConclusionWe show for the first time that CQ treatment promotes the expansion of Treg cells, corroborating previous reports indicating that chloroquine has immunomodulatory properties. Our results also show that CQ treatment suppress the inflammation in the CNS of EAE-inflicted mice, both in prophylactic and therapeutic approaches. We hypothesized that the increased number of regulatory T cells induced by the CQ treatment is involved in the reduction of the clinical signs of EAE.

TLR-2 Activation Induces Regulatory T Cells and Long-Term Suppression of Asthma Manifestations in Mice

Asthma is a chronic inflammatory disease of the airways characterized by variable airway obstruction and airway hyperresponsiveness (AHR). The T regulatory (Treg) cell subset is critically important for the regulation of immune responses. Adoptive transfer of Treg cells has been shown to be sufficient for the suppression of airway inflammation in experimental allergic asthma. Intervention strategies aimed at expanding the Treg cell population locally in the airways of sensitized individuals are therefore of high interest as a potential therapeutic treatment for allergic airway disease. Here, we aim to test whether long-term suppression of asthma manifestations can be achieved by locally expanding the Treg cell subset via intranasal administration of a TLR-2 agonist. To model therapeutic intervention aimed at expanding the endogenous Treg population in a sensitized host, we challenged OVA-sensitized mice by OVA inhalation with concomitant intranasal instillation of the TLR-2 agonist Pam3Cys, followed by an additional series of OVA challenges. Pam3Cys treatment induced an acute but transient aggravation of asthma manifestations, followed by a reduction or loss of AHR to methacholine, depending on the time between Pam3Cys treatment and OVA challenges. In addition, Pam3Cys-treatment induced significant reductions of eosinophils and increased numbers of Treg cells in the lung infiltrates. Our data show that, despite having adverse acute effects, TLR2 agonist treatment as a therapeutic intervention induces an expansion of the Treg cell population in the lungs and results in long-term protection against manifestation of allergic asthma upon subsequent allergen provocation. Our data indicate that local expansion of Tregs in allergic airway disease is an interesting therapeutic approach that warrants further investigation.

CCR5-dependent recruitment of T cells and regulatory T cells contribute to squamous cell carcinoma development

Event Abstract Back to Event CCR5-dependent recruitment of T cells and regulatory T cells contribute to squamous cell carcinoma development Carine E. Oliveira1, Thais H. Gasparoto1, Caudia R. Pinheiro1, Karen A. Cavassani2, Gustavo P. Garlet1, João S. Silva3 and Ana P. Campanelli1* 1 Bauru School of Dentistry – University of São Paulo, Department of Biological Sciences, Brazil 2 Medical School, University of Michigan, Department of Pathology, United States 3 School of Medicine of Ribeirão Preto – University of São Paulo, Department of Biochemistry and Immunology , Brazil Squamous cell carcinoma (SCC) is one of the most common human cancers worldwide. Recent work show that Treg cells have a critical role in modulating the antitumor immune responses and consequently the SCC development. Because the accumulation of Tregs at the tumor site is due in part to selective recruitment through the CCR5 and the CCR5-associated chemokines, we investigated the role of CCR5 in the SCC development. The results showed that CCR5 deficient mice are more efficient in controlling papilloma incidence than wild-type (WT) mice. In the absence of CCR5, the percentage of leukocytes in the lymph nodes and tumor was significantly increased. Moreover, the adoptive transfer of CD4+CD25+CCR5+, CD4+CD25−CCR5+ and CD8+CCR5+ T cells to CCR5−/− mice resulted in an increased papilloma incidence. Interestingly, adoptive transfer of Treg cells induced a SCC lesion more undifferentiated than all other groups and a higher infiltration of macrophage, dendritic cells and myeloid suppressive cells. Overall, CCR5 is a key receptor for the migration of T cells to the SCC lesions. Thus, a tight control of CCR5+ T cells migration, especially Treg cell, to the SCC lesions could be an important mechanism for avoiding tumor progression. Keywords: Squamous cell carcinoma, chemokine, regulatory T cell., CCR5, tumor Conference: 15th International Congress of Immunology (ICI), Milan, Italy, 22 Aug - 27 Aug, 2013. Presentation Type: Abstract Topic: Adaptive Immunity Citation: Oliveira CE, Gasparoto TH, Pinheiro CR, Cavassani KA, Garlet GP, Silva JS and Campanelli AP (2013). CCR5-dependent recruitment of T cells and regulatory T cells contribute to squamous cell carcinoma development. Front. Immunol. Conference Abstract: 15th International Congress of Immunology (ICI). doi: 10.3389/conf.fimmu.2013.02.00878 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 21 Jun 2013; Published Online: 22 Aug 2013. * Correspondence: Dr. Ana P Campanelli, Bauru School of Dentistry – University of São Paulo, Department of Biological Sciences, Bauru, Brazil, apcampan@usp.br Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Carine E Oliveira Thais H Gasparoto Caudia R Pinheiro Karen A Cavassani Gustavo P Garlet João S Silva Ana P Campanelli Google Carine E Oliveira Thais H Gasparoto Caudia R Pinheiro Karen A Cavassani Gustavo P Garlet João S Silva Ana P Campanelli Google Scholar Carine E Oliveira Thais H Gasparoto Caudia R Pinheiro Karen A Cavassani Gustavo P Garlet João S Silva Ana P Campanelli PubMed Carine E Oliveira Thais H Gasparoto Caudia R Pinheiro Karen A Cavassani Gustavo P Garlet João S Silva Ana P Campanelli Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

A two-hit model of autoimmunity: lymphopenia and unresponsiveness to TGF-β signaling

A two-hit model of autoimmunity: lymphopenia and unresponsiveness to TGF-β signaling

Granzymes are necessary for suppressive function of regulatory T cells

Purpose Regulatory T (Treg) cells are an essential subset of CD4+ T cells that induce and maintain immunological tolerance. Preclinical animal models have demonstrated that adoptive transfer of Treg cells can prevent or cure diabetes, multiple sclerosis (EAE), inflammatory bowel disease, lupus, arthritis, and graft versus host disease. Defects in Treg cell function and number have been described in a number of different human autoimmune diseases including diabetes, multiple sclerosis, rheumatoid arthritis and juvenile idiopathic arthritis. These data suggest that manipulation of Treg cells may be a useful therapeutic intervention. Treg cells are marked by expression of the forkhead/winged helix transcription factor Foxp3, which is essential for their regulatory functions. Treg cells are well known to mediate their immunomodulatory effects through TGF-b, IL-10 and CTLA-4. Recent work has also suggested a role for the granule/exocytosis pathway in Treg cell suppressive function. Granzyme A and granzyme B (gzm A and gzm B, respectively) mRNAs are expressed at high levels in Treg cells, and Treg cells from gzm B–/– mice showed defects in suppression in vitro. To further examine the role of granzymes in the function of Treg cells in vivo, we used a T cell transfer model of colitis. In this model, naive CD45RBhigh CD4+ T cells transferred to RAG–/– mice and undergo homeostatic expansion and activation.This process results in colitis manifested clinically by weight loss and shortened survival. Previous work has shown that a subset of the transferred conventional T cells develop into Foxp3+ iTreg cells and that these iTreg cells are necessary to mitigate colitis when present together with natural Treg cells (nTreg) cells derived in the thymus. Methods CD45RBhigh T cells from mice expressing a Foxp3EGFP fusion protein and additionally deficient in gzm A or gzm B are transferred to RAG-/mice.In these mice, EGFP expression marks iTreg which have developed in situ. Mice were weighed twice weekly and euthanized when moribund or when they have lost more than 1520% of their initial weight. Mesenteric lymph nodes T cells were analyzed for expression of EGFP.

TNFR2 on non‐haematopoietic cells is required for Foxp3+ Treg‐cell function and disease suppression in EAE

The TNF/TNFR system exerts multiple proinflammatory and immunosuppressive functions in the pathogenesis of chronic inflammation and autoimmunity. In EAE, the experimental model of Multiple Sclerosis (MS), genetic ablation of TNFR2, results in exacerbated immune reactivity and chronic disease course. The underlying mechanism driving this immunosuppressive function of TNFR2 remains unclear. We show here that chronic exacerbated EAE in TNFR2 KO mice is associated with increased Th17-cell responses and reduced numbers of Foxp3(+) Treg cells both in the spinal cord and peripheral lymphoid organs. Treg cells from TNFR2-deficient animals developing EAE show decreased proliferative and suppressive functions, both ex vivo and in vivo, and appear responsible for the exacerbated non-remitting disease, as evidenced by phenotypic rescue following adoptive transfer of Treg cells from WT but not TNFR2(-/-) donors. Reciprocal BM transplantation experiments between WT and TNFR2-deficient mice demonstrated that the capacity of TNFR2 to support Treg-cell expansion and function during EAE is non-intrinsic to Treg or other haematopoietic cells but requires expression of TNFR2 in radiation-resistant cells of the host. These results reveal a previously unsuspected role for non-haematopoietic TNFR2 in modulating Treg-cell expansion and immune suppression during development of autoimmunity and suggest that a similar mechanism may affect chronicity and relapses characterizing human autoimmune disease, including MS.

Type 1 Diabetes in BioBreeding Rats Is Critically Linked to an Imbalance between Th17 and Regulatory T Cells and an Altered TCR Repertoire

Diabetes-prone BioBreeding (DP-BB) rats spontaneously develop type 1 diabetes mellitus (T1DM) on grounds of their MHC haplotype RT1(u) and a point mutation in the Gimap5 gene. In this study, we report that DP-BB rats exhibit an increasingly severe imbalance, in particular between Th17 and regulatory T (T(reg)) cells, within the first months of age. This can be assigned to an excess in effector T cells because neither the percentage nor the function of the T(reg) cells is compromised. Flow cytometric analysis of Vbeta segment usage and CDR3 spectratyping further suggest that the disturbed repertoire of peripheral T cells may also contribute to the development of T1DM in DP-BB rats. Importantly, expansion of T(reg) cells in vivo by means of a CD28 superagonistic Ab as well as adoptive transfer of T(reg) cells efficiently interferes with the development of T1DM in DP-BB rats, whereas treatment with conventional Th cells does not afford protection. Using a newly generated strain of enhanced GFP transgenic rats, we could further demonstrate that the transferred T(reg) cells persist in the recipient rats for several months and partially correct the imbalance between Th17 and T(reg) cells. Thus, our data support the hypothesis that unchecked effector T cell action and a disturbed T cell repertoire contribute to the development of T1DM in DP-BB rats, which may also have implications for a better understanding of the human disease.

Regulatory T cells contribute to the protective effect of ischemic preconditioning in the kidney

Reperfusion following ischemia is associated with acute kidney injury and inflammation. Using a mouse model, we exposed the kidney to a nonlethal period of ischemia, rendering it refractory to future ischemia-induced dysfunction. This ischemic preconditioning is partially mediated by Treg lymphocytes that suppress immune responses. We found that this maneuver significantly inhibited the accumulation of neutrophils and macrophages, tubular necrosis, and loss of kidney function caused by a subsequent ischemia/reperfusion injury 1 week later. The initial ischemia/reperfusion caused a significant increase in CD4(+)CD25(+)FoxP3(+) and CD4(+)CD25(+)IL-10(+) Treg cells within the kidney at 7 days of reperfusion. Treatment of preconditioned mice with a Treg cell-depleting antibody (PC61) reversed the effect of preconditioning on kidney neutrophil accumulation and partially inhibited the functional and histological protection of preconditioning. Adoptive transfer of Treg cells in naive mice, before ischemia/reperfusion, mimicked the protective and anti-inflammatory effects of ischemic preconditioning on the kidney. These studies highlight the role of Treg cells in ischemic preconditioning.

Bilirubin Promotes De Novo Generation of T Regulatory Cells

We have previously demonstrated that bilirubin administration to the recipient induces tolerance towards islet cell transplants across a complete MHC mismatch in a mouse model. Here we assess the mechanisms of such protection. Bilirubin treatment of recipients improved function of islet allografts by suppressing expressions of proinflammatory and proapoptotic genes in those islets and by increasing Foxp3(+) T regulatory (Treg) cells at the site of transplanted islets at various days after transplantation. No prolongation of graft survival was observed in recipients treated with bilirubin when CD4(+)CD25(+) T cells were predepleted from those recipients, indicating that Treg cells are necessary for the protective effect of bilirubin. Adoptive transfer of Treg cells from tolerant mice into Rag1(-/-) recipients resulted in long-term acceptance of skin allografts in an alloantigen-specific manner, suggesting that Treg cells are sufficient to induce tolerance. In addition, bilirubin treatment promoted de novo generation of Treg cells in Rag1(-/-) recipients. Thus, bilirubin treatment to the recipients prolongs islet allograft survival via a Treg-dependent manner in which CD4(+)CD25(+) Treg cells are both necessary and sufficient for tolerance induction and graft acceptance. Bilirubin treatment promotes de novo generation of Treg cells that might account for the protective effects of bilirubin given to recipients.

Regulatory T Cells Ameliorate Angiotensin II–Induced Cardiac Damage

Hypertensive target organ damage, especially cardiac hypertrophy with heart failure and arrhythmia, is a major source of morbidity and mortality. Angiotensin II, a major mediator of hypertension and cardiac damage, has proinflammatory properties. Inflammation and activation of the immune system play a pivotal role in pathogenesis of hypertensive target organ damage. However, the role of immunosuppressive CD4+CD25+ regulatory T (Treg) cells in the pathogenesis of hypertensive target organ damage is unexplored. We conducted adoptive transfer of Treg cells into angiotensin II-infused hypertensive mice. Treg cell recipients exhibited improved cardiac hypertrophy and less cardiac fibrosis despite sustained hypertension. Amelioration of cardiac morphology was accompanied by an improvement in arrhythmogenic electric remodeling, indicating the functional significance of the enhanced cardiac morphology. Delocalization of the connexin 43 gap junction protein is one of the major pathomechanisms in electric remodeling. Pronounced connexin 43 immunoreactivity was found at the lateral borders of cardiomyocytes in angiotensin II-treated mice. In contrast, connexin 43 was restricted to the intercalated disk regions in sham controls. Surprisingly, angiotensin II+Treg-treated mice showed normal connexin 43 gap junction protein localization. Adoptive Treg cell transfer resulted in a marked reduction in cardiac CD4+, CD8+, and CD69+ cell and macrophage infiltration. Immunosuppressive effects of transferred Treg cells ameliorated cardiac damage and accounted for the improved electric remodeling independently of blood pressure-lowering effects. Our results provide new insights into the pathogenesis of hypertensive cardiac damage and could therefore lead to new therapeutic approaches that involve manipulation of the immune system.