Rapamycin combined with donor immature dendritic cells promotes liver allograft survival in association with CD4(+) CD25(+) Foxp3(+) regulatory T cell expansion

Sirolimus vs mycophenolate moftile in Tacrolimus based therapy following induction with Antithymocyte globulin promotes regulatory T cell expansion and inhibits RORγt and T-bet expression in kidney transplantation

BACKGROUND

Accumulating evidence suggests that regulatory T cells (Tregs) have a crucial role in immune tolerance and long-term graft survival. However, the influence of immunosuppressive drugs on the level of Tregs has not been fully understood. Therefore we prospectively compare the effect of two different calcineurin inhibitor (CNI)-based immunosuppression protocols on Tregs frequencies and expression of regulatory and effector T cell-related genes in renal transplant recipients.

METHODS

The study included 24 renal transplant recipients who received induction therapy (Antithymocyte globulin) and were on triple immunosuppressive therapy so that one group was on Tacrolimus (Tac), mycophenolate moftile (MMF) and prednisolone (P) whereas another group was on Tac, Sirolimus (SRL) and P. The frequency of circulating Treg cells was analyzed by flow cytometry before and 4 months after transplantation. Also, the mRNA expression of FOXP3, T-bet, GATA3 and RORγt was examined by quantitative RT-PCR before and 4 months after transplantation.

RESULTS

Compared to baseline, the frequency of CD4+ CD25+ FOXP3+ Treg cells was significantly increased in the all patients following transplantation. Patients who received Tac/MMF had significantly higher CD4+ CD25+ FOXP3+ Treg cells compared to patients who received Tac/SRL. There was no a significant difference in the frequency of CD3+CD8+ CD28- Tregs between two different calcineurin inhibitor (CNI)-based immunosuppression protocols. FOXP3 mRNA levels in the patients who received Tac/MMF were increased 4 months after transplantation and the expression was significantly higher than patients who received Tac/SRL. On the other hand, T-bet and RORγt expression levels were significantly lower in the Tac/SRL group in comparison to Tac/MMF group. We did not observe any significant difference in GATA3 mRNA level between the two groups.

CONCLUSIONS

Our results suggest that although Tac/MMF-containing immunosuppressive regimen could significantly increase the frequency of CD4+ CD25+ FOXP3+ Tregs, unlike to Tac/SRL-containing regimen, it could not significantly decrease the expression levels of RORγt and T-bet.

Exosomes Derived From T Regulatory Cells Suppress CD8+ Cytotoxic T Lymphocyte Proliferation and Prolong Liver Allograft Survival

BACKGROUND CD8+ cytotoxic T lymphocytes (CTLs) have been proved to exert crucial roles in immunological rejection. Exosomes (EXOs) secreted by CD4+CD25+ regulatory T (Treg) cells is believed to be deeply involved in immune regulation. Nevertheless, whether immunomodulatory effect of CD4+CD25+ Treg cells on CD8+ CTL depends on EXOs remains unknown and needs to be explored. MATERIAL AND METHODS We purified CD4+CD25+ Treg cells followed by in vitro amplification. EXOs in culture supernatants of Treg cells was separated and identified. The effect of CD4+CD25+ Treg cells and CD4+CD25+ Treg cells-derived EXOs on CD8+ CTL viability, proliferation, cell cycle mRNA, intracellular cytokines, and protein expression were investigated. RESULTS We successfully obtained EXOs from CD4+CD25+ Treg cells. The inhibition effect of EXOs on CD8+ CTL was concentration-dependent. In addition, the inhibition effect of CD4+CD25+ Treg cells could be reversed by GW4869, an EXOs inhibitor. The inhibition effect was associated with the regulation of IFN-γ and perforin. Our in vivo experiments proved that natural CD4+CD25+ Treg cells-released EXOs can prolong liver allograft survival. CONCLUSIONS CD4+CD25+ Treg cells-derived EXOs could become an alternative tool for manipulating the immune system to discover novel underlying immunomodulatory mechanisms.

Galectin-1-induced tolerogenic dendritic cells combined with apoptotic lymphocytes prolong liver allograft survival

Donor-derived tolerogenic dendritic cells (DCs) and apoptotic lymphocytes (ALs) are practical tools for controlling rejection after transplantation by targeting direct and indirect allorecognition pathways, respectively. To date, few studies have investigated the combination of donor-derived tolerogenic DCs and ALs infusion in organ transplantation protection. In the present study, we generated galectin-1-induced tolerogenic DCs (DC_gal-1s) and ultraviolet irradiation-induced ALs with stable immune characteristics in vitro and potential immune regulatory activity in vivo. A rat model of acute liver transplant rejection was established, and the intrinsic tolerogenic profiles associated with the short-term alleviation of rejection and the long-term maintenance of tolerance in the absence of immunosuppressive drugs were evaluated. The DC_gal-1-AL treatment prolonged allograft survival more significantly than a transfusion of DC_gal-1s or ALs alone. This benefit was associated with CD4⁺ Treg cell expansion and decreased interferon (IFN)-γ⁺ T cell levels. Moreover, DC_gal-1-AL treatment led to different cytokine/chemokine changes in the allograft and peripheral blood, that indicated an alleviation of local and systemic inflammation on day 7 post-transplantation. TGF-β1 and TGF-β2 were significantly increased in the long-term surviving allografts after DC_gal-1-AL treatment. Our results indicate that the combination of DC_gal-1s with ALs effectively prolongs liver allograft survival and represents a novel therapeutic strategy for liver transplant rejection.

Delayed Donor Bone Marrow Infusion Induces Liver Transplant Tolerance

BACKGROUND

Nonmyeloablative conditioning followed by donor bone marrow infusion (BMI) to induce tolerance has not been robustly tested in liver transplantation (LT) and may be unsafe at the time of LT. We hypothesized T cell-depleted BMI is effective in inducing tolerance when delayed after LT, resulting in potentially safer future clinical applications.

METHODS

Nonimmunosuppressed syngeneic (Lewis to Lewis) and allogeneic (ACI to Lewis) rat LT transplants were initially performed as controls. Three experimental allogeneic LT groups were treated with tacrolimus (TAC) for 3 to 4 weeks and then underwent: (1) TAC withdrawal alone; (2) nonmyeloablative conditioning (anti-αβTCR mAb + total body irradiation [300 cGy]) followed by TAC withdrawal; (3) Nonmyeloablative conditioning + donor BMI (100 × 10 T cell-depleted bone marrow cells) followed by TAC withdrawal.

RESULTS

All group 1 recipients developed chronic rejection. Group 2 had long-term survival but impaired liver function and high donor-specific antibody (DSA) levels. In contrast, group 3 (conditioning + BMI) had long-term TAC-free survival with preserved liver function and histology, high mixed chimerism and blood/liver/spleen CD4 + CD25 + Foxp3+ regulatory T cells, and low DSA titers, similar to syngeneic grafts. While donor-specific tolerance was observed post-BMI, graft-versus-host disease was not.

CONCLUSIONS

These results support that donor-specific tolerance can be achieved with BMI even when delayed after LT and this tolerance correlates with increased mixed chimerism, regulatory T cell generation, and diminished DSA.

Harnessing the properties of dendritic cells in the pursuit of immunological tolerance

The acquisition of self-perpetuating, immunological tolerance specific for graft alloantigens has long been described as the "holy grail" of clinical transplantation. By removing the need for life-long immunosuppression following engraftment, the adverse consequences of immunosuppressive regimens, including chronic infections and malignancy, may be avoided. Furthermore, autoimmune diseases and allergy are, by definition, driven by aberrant immunological responses to ordinarily innocuous antigens. The re-establishment of permanent tolerance towards instigating antigens may, therefore, provide a cure to these common diseases. Whilst various cell types exhibiting a tolerogenic phenotype have been proposed for such a task, tolerogenic dendritic cells (tol-DCs) are exquisitely adapted for antigen presentation and interact with many facets of the immune system: as such, they are attractive candidates for use in strategies for immune intervention. We review here our current understanding of tol-DC mediated induction and maintenance of immunological tolerance. Additionally, we discuss recent in vitro findings from animal models and clinical trials of tol-DC immunotherapy in the setting of transplantation, autoimmunity and allergy which highlight their promising therapeutic potential, and speculate how tol-DC therapy may be developed in the future.

Tolerance in liver transplantation: Biomarkers and clinical relevance

Transplantation is the optimal treatment for end-stage organ failure, and modern immunosuppression has allowed important progress in short-term outcomes. However, immunosuppression poorly influences chronic rejection and elicits chronic toxicity in current clinical practice. Thus, a major goal in transplantation is to understand and induce tolerance. It is well established that human regulatory T cells expressing the transcription factor FoxP3 play important roles in the maintenance of immunological self-tolerance and immune homeostasis. The major regulatory T cell subsets and mechanisms of expansion that are critical for induction and long-term maintenance of graft tolerance and survival are being actively investigated. Likewise, other immune cells, such as dendritic cells, monocyte/macrophages or natural killer cells, have been described as part of the process known as "operational tolerance". However, translation of these results towards clinical practice needs solid tools to identify accurately and reliably patients who are going to be tolerant. In this way, a plethora of genetic and cellular biomarkers is raising and being validated worldwide in large multi-center clinical trials. Few of the studies performed so far have provided a detailed analysis of the impact of immunosuppression withdrawal on pre-existing complications derived from the long-term administration of immunosuppressive drugs and the side effects associated with them. The future of liver transplantation is aimed to develop new therapies which increase the actual low tolerant vs non-tolerant recipients ratio.

Effects of Adoptive Transfer of Tolerogenic Dendritic Cells on Allograft Survival in Organ Transplantation Models: An Overview of Systematic Reviews

Objective. To dissect the efficacy of Tol-DC therapy with or without IS in multiple animal models of transplantation. Methods and Results. PubMed, Medline, Embase, and the Cochrane Library were searched for reviews published up to April 2015. Six systematic reviews and a total of 61 articles were finally included. Data were grouped by organ transplantation models and applied to meta-analysis. Our meta-analysis shows that Tol-DC therapy successfully prolonged allograft survival to varying extents in all except the islet transplantation models and with IS drugs further prolonged the survival of heart, skin, and islet allografts in mice, but not of heart allografts in rats. Compared with IS drugs alone, Tol-DC therapy with IS extended islet allograft survival in rats but failed to influence the survival of skin, small intestine, and heart allografts in rats or of heart and skin allografts in mice. Conclusion. Tol-DC therapy significantly prolonged multiple allograft survival and further prolonged survival with IS. However, standardized protocols for modification of Tol-DC should be established before its application in clinic.

Immunosuppressive potency of mechanistic target of rapamycin inhibitors in solid-organ transplantation

Mammalian target of rapamycin, also known as mechanistic target of rapamycin (mTOR) is a protein kinase that belongs to the PI3K/AKT/mTOR signaling pathway, which is involved in several fundamental cellular functions such as cell growth, proliferation, and survival. This protein and its associated pathway have been implicated in cancer development and the regulation of immune responses, including the rejection response generated following allograft transplantation. Inhibitors of mTOR (mTORi) such as rapamycin and its derivative everolimus are potent immunosuppressive drugs that both maintain similar rates of efficacy and could optimize the renal function and diminish the side effects compared with calcineurin inhibitors. These drugs are used in solid-organ transplantationtoinduceimmunosuppression while also promoting the expansion of CD4+CD25+FOXP3+ regulatory T-cells that could favor a scenery of immunological tolerance. In this review, we describe the mechanisms by which inhibitors of mTOR induce suppression by regulation of these pathways at different levels of the immune response. In addition, we particularly emphasize about the main methods that are used to assess the potency of immunosuppressive drugs, highlighting the studies carried out about immunosuppressive potency of inhibitors of mTOR.

Topical application of sphingosine 1-phosphate receptor 1 prolongs corneal graft survival in mice

The present study aimed to investigate the effects of topical application of sphingosine 1‑phosphate receptor 1 (S1P1) on allogeneic corneal transplantation in mice. A total of 45 BALB/c mice received corneal grafts from C57BL/6 donors. The recipients were randomly divided into three groups and treated with eye drops containing 0.5% S1P1, 1% cyclosporine A or saline as a negative control. The serum levels of interleukin (IL)‑2, IL‑10, tumor growth factor (TGF)‑β1 and interferon (IFN)‑γ were measured by ELISA. The numbers of CD4+ T cell and T‑regulatory (Treg) cell phenotypes were measured by flow cytometry. The cytokine mRNA expression was analyzed by quantitative polymerase chain reaction. The results demonstrated that corneal graft survival was prolonged in the S1P1 group [mean survival time (MST), 24.11±1.58 days], and 1% cyclosporine A (MST, 25.0±1.91 days) compared with the controls (MST, 13.44±0.48 days; P<0.01). S1P1 and cyclosporine A decreased CD4+ T‑cell levels (P<0.05) in the peripheral blood compared with those of the controls. However, an increase of CD4+ T cells in the spleen was noted in the S1P1 group (P<0.05) and Treg cells were also increased in the cervical lymph nodes in the S1P1 group (P<0.01). TGF‑β1 mRNA transcription in the corneal grafts increased following treatment with S1P1 (P<0.05) and TGF‑β1 in the serum following treatment with S1P1 also increased (P<0.01). In conclusion, S1P1 had a significant effect in corneal allograft rejection inhibition.

Adoptive transfusion of tolerogenic dendritic cells prolongs the survival of liver allograft: a systematic review

OBJECTIVES

To systematically review the effects of tolerogenic dendritic cells (Tol-DCs) induced by different methods on liver transplantation and their possible mechanisms of action.

METHODS

PubMed and EMbase were searched for relevant articles through 31 December 2013. The effects of Tol-DCs on liver allograft survival were semiquantitatively evaluated, and the possible mechanisms by which Tol-DCs prolong graft survival were analyzed.

RESULTS

Seven articles were included, and classified according to methods of induction, sources, and methods of infusing Tol-DCs. Tol-DCs induced from immature DCs (imDCs), with cytokines, and by gene modification induced liver transplant tolerance for 33.1 ± 32.5 days (2.7-fold vs. control), 26.17 ± 16.20 days (1.8-fold vs. control), and 11.7 ± 1.6 days (2.3-fold vs. control), respectively. DCs derived from recipient bone marrow, donor bone marrow, and donor spleen induced liver transplant tolerance for 51.0 ± 0.0 days (5.9-fold vs. control), 21.4 ± 26.8 days (2.4-fold vs. control), and 15.0 ± 0.0 days (2.3-fold vs. control), respectively. The primary mechanisms by which Tol-DCs induce liver transplant tolerance were the induction of T-cell hyporeactivity and Th2 differentiation.

CONCLUSIONS

Tol-DCs induced by three different methods could extend liver allograft survival, with imDCs showing optimal results. The optimal infusion method was intravenous injection of 1-2 × 10(6) Tol-DC, similar to findings in renal transplantation. Tol-DCs prolonged liver transplant tolerance more than renal transplant tolerance.

CD4+CD25+Foxp3+ Treg cells and liver transplant tolerance

Several subgroups of regulatory T (Treg) cells play crucial roles in both induction and maintenance of immune tolerance to self-antigens and alloantigens. The most extensively and comprehensively studied regulatory T cell subgroup is CD4⁺CD25⁺Foxp3⁺ Treg cells. Numerous studies indicate that insufficiency or dysfunction of CD4⁺CD25⁺Foxp3⁺ Treg cells is responsible for the development of many autoimmune diseases and rejections after organ transplantation. Therefore, harnessing CD4⁺CD25⁺Foxp3⁺ Treg cells may provide a promising approach for inducing and maintaining liver transplant tolerance. In this review, we will focus on the history and classification of regulatory T cells, the mechanisms by which regulatory T cells induce transplant tolerance and their roles in liver transplant tolerance.

Systemic application of sphingosine 1-phosphate receptor 1 immunomodulator inhibits corneal allograft rejection in mice

PURPOSE

This study aims to investigate the effects of systemic application of sphingosine 1-phosphate receptor 1(S1P1) on allogeneic corneal transplantation in mice.

METHODS

A total of 112 BALB/c mice received corneal grafts from C57BL/6 donors. Recipients were randomly divided into seven groups and treated with intraperitoneal injections of S1P1 (5 mg/kg/days), cyclosporine A (5 mg/kg/days), dexamethasone (1 mg/kg/days) and rapamycin (2 mg/kg/days). S1P1was combined with rapamycin or cyclosporine A, and saline served as negative control. Serum levels of IL-2, IL-10, TGF-β1 and IFN-γ were measured by Elisa. The numbers of CD4+ T and regulatory (Treg) cell phenotype were measured by flow cytometry. Cytokine mRNA expression was analysed by real-time quantitative PCR. CD4+ T cells and cytokines were histologically identified by immunofluorescence staining.

RESULTS

Corneal graft survival was prolonged by intraperitoneal injections in S1P1 alone (mean survival time MST, 35.3 ± 5.6 days), S1P1 combined with rapamycin (MST, 38.7 ± 6.5 days) or S1P1 and cyclosporine A (MST, 32.7 ± 4.8 days) compared with the controls (MST, 14.6 ± 0.2 days; n = 5, p < 0.01). S1P1 alone increased CD4+ T (p < 0.01) and Treg cells (p < 0.01; n = 5) in the cervical and mesenteric lymph nodes compared with the controls and S1P1 + rapamycin (p < 0.05; n = 5). TGF-β1 and IL-10 mRNA transcriptions in corneal grafts following S1P1+ rapamycin increased (both p < 0.01; n = 3), and TGF-β1 and IL-10 in the serum level following S1P1 alone increased (both p < 0.01; n = 3). These results paralleled the findings obtained from immunofluorescence.

CONCLUSION

S1P1 has significant effect in corneal allograft rejection inhibition. The combined treatment of S1P1 and rapamycin results in synergistic effect.

Circulating CD4+CD25+ regulatory T cells in the pathobiology of ulcerative colitis and concurrent primary sclerosing cholangitis

BACKGROUND

Immunopathogenetic features of primary sclerosing cholangitis (PSC) in ulcerative colitis (UC) still remains unclear. Peripheral blood CD4+CD25+ regulatory T cells have a key role in the induction and maintenance of peripheral self-tolerance and inhibit several organ-specific autoimmune diseases. Therefore, CD4+CD25+ T cells are believed to play an essential role in autoimmune diseases. The aim of the present study is to analyze the role of CD4+CD25+ T cells in the pathogenesis of UC-associated PSC.

METHODS

This study evaluated the levels of CD4+CD25+ T cells in peripheral blood mononuclear cells (PBMC) of 27 UC patients with PSC and 20 UC patients as controls. CD4+CD25+ T cells were isolated from PBMC with a direct immunofluorescence technique, using mice monoclonal antibodies namely FITC-labeled anti-CD4 and PE-labeled anti-CD25. In each patient, CD4+CD25+ T cells percentage in PBMC were studied by flow cytometry, and then the number of CD4+CD25+ T cells were calculated.

RESULTS

Twenty-seven UC patients with PSC and 20 UC patients without PSC as controls were enrolled in the present study. The percentage of CD4+CD25+ regulatory T cells among PBMC were significantly elevated in UC + PSC patients compared with UC patients without PSC (p = 0.04).

CONCLUSIONS

CD4+CD25+ T cells were found to be elevated in UC patients with PSC suggesting a partial role of activated T cell response in the disease pathophysiology. Our findings imply that CD4+CD25+ regulatory T cells may play a key role in the immunopathogenesis of UC-associated PSC and may affect the therapeutic management of these diseases.