Islet Allograft Survival Research Articles

Low energy X-ray (grenz ray) treatment of purified islets prior to allotransplant markedly decreases passenger leukocyte populations

ABSTRACTGrenz rays, or minimally penetrating X-rays, are known to be an effective treatment of certain recalcitrant immune-mediated skin diseases, but their use in modulating allograft rejection has not been tested. We examined the capacity of grenz ray treatment to minimize islet immunogenicity and extend allograft survival in a mouse model. In a preliminary experiment, 1 of 3 immunologically intact animals demonstrated long-term acceptance of their grenz ray treated islet allograft. Further experiments revealed that 28.6% (2 of 7) grenz ray treated islet allografts survived >60 d. A low dose of 20Gy, was important; a 4-fold increase in radiation resulted in rapid graft failure, and transplanting a higher islet mass did not alter this outcome. To determine whether increased islet allograft survival after grenz treatment would be masked by immunosuppression, we treated the recipients with CTLA-4 Ig, and found an additive effect, whereby 17.5% more animals accepted the graft long-term versus those with CTLA-4 Ig alone. Cell viability assays verified that islet integrity was maintained after treatment with 20Gy. As well, through splenocyte infiltration analysis, donor CD4+ T cell populations 24-hours after transplant were decreased by more than16-fold in recipients receiving irradiated islets compared with control. Donor CD8+ T cell populations, although less prevalent, decreased in all treatment groups compared with control. Our results suggest that brief treatment of isolated islets with low energy grenz rays before allotransplantation can significantly reduce passenger leukocytes and promote graft survival, possibly by inducing donor dendritic cells to differentiate toward a tolerogenic phenotype.

Effect of preventive treatment in EAE mouse model transplanted with DN T cells transformed from CD4 T cells

Multiple sclerosis (MS) is an immune-mediated demyelinating disease of the central nervous system (CNS). Experimental autoimmune encephalomyelitis (EAE) has long served as an animal model for human MS. Both diseases are characterized by inflammation and demyelination of the CNS. Lots of study confirmed that Th1 and Th17 cells could aggravate the illness, while Foxp3+ regulatory T cells (Treg cells) could inhibit the autoimmune reaction and limit disease progression. However, it has been studied that both the number and immune suppression function of Treg cells were reduced in EAE mice, and although myelin specific Treg cells accumulated in the CNS, it failed to control autoimmune inflammation. Based on that, promoting immune regulation by other regulatory cells may be a new strategy to restore immune homeostasis and control EAE. Many studies have demonstrated that in peripheral lymphoid tissues of normal mice and healthy humans, 1% to 3% of T cell receptor positive T cells are double negative T cells (DN T cells), which capable of down regulating immune responses. We have identified a new differentiation pathway for the conversion of CD4 T cells to DN T cells, which could large amount DN T cells in vitro in a short time. We have showed that the converted DN T cells retained a stable phenotype and expressed a unique set of cell surface markers and gene profiles. These cells were highly potent in suppressing allo- and auto-immune responses both in vitro and in vivo in an antigen specific manner. Adoptive cell therapy using these antigen specific DN T cells could prevent and cure autoimmune diabetes and promote islet allograft survival in NOD mice. In a ConA mediated liver injury model, CD4 T cell converted DN T cells exerted significant protection against immune mediated liver injury and maintained the homeostasis of the immune system. Up to now, there is no report on the role of these converted DNT cells in mouse EAE model. In this study, we further explored the protection and its mechanism of DN T cells on EAE. CD4 T cells were converted to antigen specific DN T cells in vitro with MOG35–55 stimulation. Then we adoptive transferred these antigen specific DN T cells to mice before EAE immunization. Time of disease onset, EAE score, mouse weight, lymphocyte infiltration were compared between EAE control group and DNT pre-treatment group, the inhibitory function of DN T cells on pathogenic CD4 T cells from EAE model were further explored. Our data showed that a single adoptive transfer of MOG35–55 primed DN T cells significantly lowered the EAE score, prevented the weight loss and reduced lymphocytes infiltration in brain tissue. DN T cells pre-treatment group contained lower plasma IL-2 and IL-4 levels compared to EAE control group. In vitro suppression assays showed DN T cells significantly suppressed the proliferation of inflammatory CD4 T cells from EAE mice. Our data suggests that DN T cells can significantly reduce the EAE severity. This preventive effect is partly due to DN T cells’ suppression on the proliferation and cytokine production of inflammatory CD4 T cells. DN T cells may have a potential clinical application in the prevention and treatment of MS.

The immunoprotection of transplant mice allograft by suppressor of cytokine signaling 1 gene-modified dendritic cells induces T cell anergy

Objective To study the regulation of high expression of suppressor of cytokine signaling 1 (SOCS1) molecule in dendritic cells (DC), and to verify the effect of DC-SOCS1 on T cell function and allografts immune protective effects in vitro and in vivo. Methods DC were modified with high affinity replication-defective adenoviral vector Ad5F35 over-expressing SOCS1. The phenotype of transduced mature DC and the function were analyzed, and the mechanism of inducing donor-specific CD4+ T cells hyporesponsiveness was explored. The mouse allogenic islet transplantation model was established, and 24 h prior to transplantation each recipient mouse was given DC cells, DC-SOCS1 cells or equal amount of phosphate buffer (PBS), named DC group, DC-SOCS1 group and control group respectively. The survival of islet grafts of transplanted recipients was observed, and on the day 7 and the rejection day post transplantation, the islet graft glucose tolerance, pathological changes, the percentage of T cell subsets in the spleen and draining lymph nodes as well as related cytokines were observed. The possible associated mechanisms of SOCS1 gene-modified mature DC mitigating immune rejection and inducing transplant tolerance in vivo were explored. Results Genetic modified Ad5F35 dramatically increased the transduction efficiency of DC compared to regular Ad. The experimental data demonstrated there was a tendency that DC overexpressing SOCS1 can induce DC low down the express of MHC and costimulatory molecules, potentiate the ability of DC-SOCS1 to induce donor specific T cell anergy in mixed lymphocytes reaction (MLR) assay. DC-SOCS1 significantly prolonged the survival time of the islet allograft with a median survival time of (37.00±2.19) days, which is significantly longer than control [(20.00±0.55) d, P=0.008] and DC group [(10.00±0.45) d, P=0.001]. Flow cytometric analysis revealed that the DC-SOCS1 dramatically reduced the population of Th1 and Tc1 [(9.92±1.57)%, P=0.027], CD4 [(17.77±2.80)%, P=0.007] and CD8 [(14.92±2.18)%, P=0.004] in spleen lymphocytes compared to control group and DC group on day 7, and a reduction of CD4 [(26.00±2.02)%, P=0.034] was observed in draining lymph nodes compared to DC group. Conclusion SOCS1 genetic modification efficiently confers mDC with low express of MHC and costimulatory molecules, and allows them to induce T cell hyporesponsiveness in vitro. The DC-SOCS1 pretreated recipients exhibit immune tolerance and prolong islet allograft survival in vivo. Key words: Dendritic cells; Gene transduction; Suppressor of cytokine signaling 1; Islet transplantation; Immune tolerance

Preloading of CD4+CD25+ Tregs to donor islets in vitro prolongs islet allograft survival

Abstract Despite extensive studies on regulatory T cells (Treg) in transplantation (Tx), Treg transfer alone remains ineffective in wild-type (WT) animal recipients, because only a small fraction of systemically administered Tregs can reach an allograft. The objective of this study is to optimize Treg suppression of islet allograft rejection via preloading Tregs to donor islets before Tx. We developed a unique system in which donor islets were activated and incubated with CD4+CD25+ Treg cells, resulting in intraislet recruitment of Tregs before Tx. Donor islets were stimulated by cytokines (IL-1β+ IL-6 + IFNβ) for 24 h and incubated with CD4+CD25+FoxP3+ Tregs for 48 h so that Tregs infiltrated the islets. Islets then were rested in the media for another 24 h before Tx. We found that “Treg-preloaded” islet allografts survived much longer than control islets with long-term islet allograft survival in the hepatic parenchyma in 43% of WT recipient mice (n=7) without any immunosuppressive drug. Importantly, Treg-preloaded islet allografts also survived significantly longer when transplanted in the hepatic parenchyma than in kidney capsule (MST = 62 vs. 39 days, n=7–8, P < 0.05) or the portal vein (MST = 62 vs. 41 days, n=7, P < 0.05). As a control, cytokine-stimulated islets with the similar culture without Treg cells were rejected at the same pace as fresh control islets (14 vs. 16 days, n=7–8, P>0.05). Moreover, BrdU staining demonstrated that graft-infiltrating Thy1.1- T cells of recipients proliferated at a slower pace in islets preloaded with Tregs than in control islets (BrdU+: 21% vs. 43%) one week after Tx. In conclusion, transplanting Treg-preloaded islets in the hepatic parenchyma is a novel approach to prolonging islet allograft survival.

C-Jun N-terminal kinase 1 defective CD4+CD25+FoxP3+ cells prolong pancreatic allograft survival in type 1 diabetic mice

Abstract CD4+CD25+FoxP3+ cells (Tregs) inhibit inflammatory immune responses to allografts. Here we found that co-transplantation of allogeneic pancreatic islets with Tregs that are defective in JNK1 signaling prolong the islet allograft survival in the liver parenchyma of the T1D mice. Deletion of the JNK1 in Tregs increased the expression of anti-apoptotic molecules Mcl-1, Bcl-Xl and anti-inflammatory cytokine IL-10 production. JNK1−/− Tregs persist for long period in the transplanted liver and prolong the islet allograft survival compared to WT Tregs. JNK1−/− Tregs demonstrated improved control of allo-inflammation compared to WT Tregs in the T1D liver upon co-transplantation. JNK1−/− Tregs specifically inhibit IL-17 and IL-21 medited alloimmune response. Inhibition of alloimmune response by JNK1−/− Tregs independently mediated through the LAG3 on its cell surface and the increased production of IL-10. Our study identifies a novel role of JNK1 signaling in the Tregs function and co-transplantation of JNK1 deficient Tregs enhances the islet allograft survival in the liver parenchyma of T1D mice.

Human α1-antitrypsin attenuates injury-induced Inflammation through interacting with high mobility group box-1 (HMGB1)

Abstract HMGB1 is involved in pathologies such as cellular injury and autoimmunity. Indeed, upon binding to immune-related receptors, HMGB1 promotes an inflammatory response, such as that might take part in pancreatic islet destruction during both autoimmune diabetes and islet transplant rejection. Specifically, elevated circulating HMGB1 levels were reported in patients with type 1 diabetes, and increased release of HMGB1 was found to correlate with injury degree and islet allograft survival. The anti-inflammatory and immune-modulatory acute-phase protein human α1-antitrypsin (hAAT) promotes islet survival in both transplantation and autoimmune diabetes models. While AAT binds to damage-released proteins, such as gp96 and HSP70, its tissue protective mechanism remains poorly understood. We now extend this observation that AAT protective activity is related to its interaction with HMGB1. Clinical-grade AAT (Glassia, Kamada Ltd., Israel), diminished recombinant HMGB1-induced inflammatory responses in mouse pancreatic islets (while restoring disrupted insulin inflammation-mediated release). Similar behavior was depicted in HMGB1-stimulated peritoneal macrophages introduced to hAAT. In addition, hAAT modulated HMGB1-inducible surface expression by altering its distribution. Lastly, we show by immunoprecipitation that HMGB1 associated proteins was positive for the presence of AAT, this is also supported by a direct ELISA. Our findings suggest that hAAT is a naturally-occurring regulator of inflammatory responses mediated by extracellular HMGB1, such that preclude outcomes of islet transplantation. hAAT may therefore be considered for therapy of cell damage-mediated pathologies in a clinically-safe manner.

Biomaterial scaffolds for localized IL-33 release to modulate the local immune environment and enhance extrahepatic allogeneic islet transplant

Abstract Allogeneic islet transplantation represents a promising therapeutic option to restore endogenous insulin production in Type-1 diabetes patients. Clinically, new methods of regulating the immune response against the islet allograft without using general immunosuppression are required. We have previously demonstrated the viability of transplanting syngeneic islets on porous poly-lactide-co-glycolide (PLG) scaffolds within the epididymal fat pad to restore long-term euglycemia. The use of a biomaterial scaffold also provides an opportunity to incorporate novel immunomodulatory factors that can modify the local immune response to transplanted cells. Due to the prevalence of ST2+ regulatory T cells and M2 macrophages linked to promotion of an anti-inflammatory phenotype within adipose tissue, we hypothesized scaffold-mediated IL-33 release could promote a tolerogenic environment to extend islet allograft survival. We found incubation of an IL-33 loaded scaffold in vitro with naïve T cells undergoing anti-CD3 TCR stimulation stimulated release of IL-13, demonstrating maintenance of IL-33 bioactivity. We found that IL-33 loaded scaffolds implanted into the epididymal fat pad expanded the CD4+ Foxp3+ population within the graft site, most strikingly amongst CD4+ Foxp3+ ST2+ Tregs. Using an allogeneic murine islet transplant model, preliminary data showed diabetic C57BL/6 recipients receiving 250 Balb/c islets on IL-33 scaffolds had extended graft survival time compared to BSA-loaded control scaffolds. Collectively, these results indicate the potential for IL-33 to modulate the local immune response to support graft function, and support ongoing studies to investigate mechanisms to extend graft survival.

Dendritic cells that highly express SOCS1 induce T-cell hypo-responsiveness and prolong islet allograft survival

The capability of dendritic cells (DCs) to induce an immune response or immune tolerance is dependent on their status. Suppressor of cytokine signaling 1 (SOCS1) is a pivotal regulator that participates in negative feedback of the JAK-STAT pathway, which plays a key role in the differentiation, activation, and maturation of DCs. DCs that highly express SOCS1 may modulate DCs, and induce immune anergy or immune tolerance. In this study, we transduced DCs with the recombinant adenovirus Ad5F35 to highly express SOCS1. The mechanisms by which DC-SOCS1 induces T-cell hypo-responsiveness were analyzed in vivo and in vitro. The data demonstrate that recipients treated with DC-SOCS1 had long islet allograft survival times, with a reduction of Th1 and Tc1 in both spleen and draining lymph nodes in vivo. In vitro assay revealed that DCs transduced with SOCS1 had low expression of major histocompatibility and costimulatory molecules, and potentiated the ability of DC-SOCS1 to induce T-cell hypo-responsiveness. Therefore, genetic modification of DCs with SOCS1 affects DC activation and maturation, inhibits T-cell proliferation and induces hypo-responsiveness, and prolongs islet allograft survival.

Targeted deletion of Traf2 allows immunosuppression-free islet allograft survival in mice.

Administration of anti-CD40 ligand (CD40L) antibodies has been reported to allow long-term islet allograft survival in non-human primates without the need for exogenous immunosuppression. However, the use of anti-CD40L antibodies was associated with thromboembolic complications. Targeting downstream intracellular components shared between CD40 and other TNF family co-stimulatory molecules could bypass these complications. TNF receptor associated factor 2 (TRAF2) integrates multiple TNF receptor family signalling pathways that are critical for T cell activation and may be a central node of alloimmune responses. T cell-specific Traf2-deficient mice (Traf2TKO) were generated to define the role of TRAF2 in CD4+ T cell effector responses that mediate islet allograft rejection in vivo. In vitro allograft responses were tested using mixed lymphocyte reactions and analysis of IFN-γ and granzyme B effector molecule expression. T cell function was assessed using anti-CD3/CD28-mediated proliferation and T cell polarisation studies. Traf2TKO mice exhibited permanent survival of full MHC-mismatched pancreatic islet allografts without exogenous immunosuppression. Traf2TKO CD4+ T cells exhibited reduced proliferation, activation and acquisition of effector function following T cell receptor stimulation; however, both Traf2TKO CD4+ and CD8+ T cells exhibited impaired alloantigen-mediated proliferation and acquisition of effector function. In polarisation studies, Traf2TKO CD4+ T cells preferentially converted to a T helper (Th)2 phenotype, but exhibited impaired Th17 differentiation. Without TRAF2, thymocytes exhibited dysregulated TNF-mediated induction of c-Jun N-terminal kinase (JNK) and canonical NFκB pathways. Critically, targeting TRAF2 in T cells did not impair the acute phase of CD8-dependent viral immunity. These data highlight a specific requirement for a TRAF2-NFκB and TRAF2-JNK signalling cascade in T cell activation and effector function in rejecting islet allografts. Targeting TRAF2 may be useful as a therapeutic approach for immunosuppression-free islet allograft survival that avoids the thromboembolic complications associated with the use of anti-CD40L antibodies.

Hematopoietic Stem Cell Mobilization Is Necessary but Not Sufficient for Tolerance in Islet Transplantation.

Overcoming the immune response to establish durable immune tolerance in type 1 diabetes remains a substantial challenge. The ongoing effector immune response involves numerous immune cell types but is ultimately orchestrated and sustained by the hematopoietic stem cell (HSC) niche. We therefore hypothesized that tolerance induction also requires these pluripotent precursors. In this study, we determined that the tolerance-inducing agent anti-CD45RB induces HSC mobilization in nonautoimmune B6 mice but not in diabetes-prone NOD mice. Ablation of HSCs impaired tolerance to allogeneic islet transplants in B6 recipients. Mobilization of HSCs resulted in part from decreasing osteoblast expression of HSC retention factors. Furthermore, HSC mobilization required a functioning sympathetic nervous system; sympathectomy prevented HSC mobilization and completely abrogated tolerance induction. NOD HSCs were held in their niche by excess expression of CXCR4, which, when blocked, led to HSC mobilization and prolonged islet allograft survival. Overall, these findings indicate that the HSC compartment plays an underrecognized role in the establishment and maintenance of immune tolerance, and this role is disrupted in diabetes-prone NOD mice. Understanding the stem cell response to immune therapies in ongoing human clinical studies may help identify and maximize the effect of immune interventions for type 1 diabetes.

Biopatterned CTLA4/Fc Matrices Facilitate Local Immunomodulation, Engraftment, and Glucose Homeostasis After Pancreatic Islet Transplantation.

Pancreatic islet transplantation (PIT) represents a potential therapy to circumvent the need for exogenous insulin in type 1 diabetes. However, PIT remains limited by lack of donor islets and the need for long-term multidrug immunosuppression to prevent alloimmune islet rejection. Our goal was to evaluate a local immunoregulatory strategy that sustains islet allograft survival and restores glucose homeostasis in the absence of systemic immunosuppression. Nanogram quantities of murine CTLA4/Fc fusion protein were controllably delivered within human acellular dermal matrix scaffolds using an inkjet-based biopatterning technology and cotransplanted with allogeneic islets under the renal capsule to create an immunoregulatory microenvironment around the islet allograft. We achieved long-term engraftment of small loads of allogeneic islet cells with 40% of MHC-mismatched mouse recipients maintaining sustained normoglycemia following pancreatic β-cell ablation by streptozotocin. Biopatterned CTLA4/Fc local therapy was associated with expansion of Foxp3+ regulatory T cells and shifts in cytokine production and gene expression from proinflammatory to regulatory profiles, thus substantially benefiting islet allografts survival and function. This study is a new paradigm for targeted therapies in PIT that demonstrates the favorable effects of immune alterations in the transplant milieu and suggests a unique strategy for minimizing systemic immunosuppression and promoting islet allograft survival.

Immunosuppression With CD40 Costimulatory Blockade Plus Rapamycin for Simultaneous Islet-Kidney Transplantation in Nonhuman Primates.

The lack of a reliable immunosuppressive regimen that effectively suppresses both renal and islet allograft rejection without islet toxicity hampers a wider clinical application of simultaneous islet-kidney transplantation (SIK). Seven MHC-mismatched SIKs were performed in diabetic cynomolgus monkeys. Two recipients received rabbit antithymocyte globulin (ATG) induction followed by daily tacrolimus and rapamycin (ATG/Tac/Rapa), and five recipients were treated with anti-CD40 monoclonal antibody (mAb) and rapamycin (aCD40/Rapa). Anti-inflammatory therapy, including anti-interleukin-6 receptor mAb and anti-tumor necrosis factor-α mAb, was given in both groups. The ATG/Tac/Rapa recipients failed to achieve long-term islet allograft survival (19 and 26 days) due to poor islet engraftment and cytomegalovirus pneumonia. In contrast, the aCD40/Rapa regimen provided long-term islet and kidney allograft survival (90, 94, >120, >120, and >120 days), with only one recipient developing evidence of allograft rejection. The aCD40/Rapa regimen was also tested in four kidney-alone transplant recipients. All four recipients achieved long-term renal allograft survival (100% at day 120), which was superior to renal allograft survival (62.9% at day 120) with triple immunosuppressive regimen (tacrolimus, mycophenolate mofetil, and steroids). The combination of anti-CD40 mAb and rapamycin is an effective and nontoxic immunosuppressive regimen that uses only clinically available agents for kidney and islet recipients.

Pretreatment of donor islets with papain improves allograft survival without systemic immunosuppression in mice

ABSTRACTAlthough current immunosuppression protocols improve the efficacy of clinical allogenic islet transplantation, T cell-mediated allorejection remains unresolved, and major histocompatibility complexes (MHCs) play a crucial role in this process. Papain, a cysteine protease, has the unique ability to cleave the extracellular domain of the MHC class I structure. We hypothesized that pretreatment of donor islets with papain would diminish the expression of MHC class I on islets, reducing allograft immunogenicity and contributing to prolongation of islet allograft survival. BALB/c islets pretreated with papain were transplanted into C57BL/6J mice as an acute allorejection model. Treatment with 1 mg/mL papain significantly prolonged islet allograft survival. In vitro, to determine the inhibitory effect on T cell-mediated alloreactions, we performed lymphocyte proliferation assays and mixed lymphocyte reactions. Host T cell activation against allogenic islet cells was remarkably suppressed by pretreatment of donor islet cells with 10 mg/mL papain. Flow cytometric analysis was also performed to investigate the effect of papain treatment on the expression of MHC class I on islets. One or 10 mg/mL papain treatment reduced MHC class I expression on the islet cell surface. Pretreatment of donor islets with papain suppresses MHC class I-mediated allograft rejection in mice and contributes to prolongation of islet allograft survival without administration of systemic immunosuppressants. These results suggest that pretreatment of human donor islets with papain may reduce the immunogenicity of the donor islets and minimize the dosage of systemic immunosuppressants required in a clinical setting.

Cell-Permeable Peptide Blocks TLR4 Signaling and Improves Islet Allograft Survival.

Toll-like receptor 4 (TLR4) activation in pancreatic β cells activates aberrant islet graft cellular pathways and contributes to immune rejection in allogeneic islet transplantation. As an approach to overcoming this problem, we determined the capacity of a 33-amino acid peptide consisting of a protein transduction domain (PTD) from the Hph-1 virus and a fragment of the intracellular domain of TLR4 from the C3H mice (PTD-dnTLR4) to block TLR4 signaling and improve allogeneic islet survival in vitro and after transplantation. The efficacy of PTD-dnTLR4 in blocking TLR4 signaling was assessed in the Raw264.7 macrophage line, in the islets, and the βTC3 cell line. In Raw264.7 cells, preculture with the peptide reduced LPS-induced NF-κB activation and production of proinflammatory cytokines (IL-1β, TNF-α, iNOS, and IL-6). In islets and β cells, preincubation with PTD-dnTLR4 suppressed LPS-induced TNF-α expression via inhibition of NF-κB activation and protected them from stress-induced cell death. In vivo, preincubation of BALB/c (H-2(d)) islets with PTD-dnTLR4 resulted in significantly longer survival than control islets in a streptozotocin-induced diabetes model (two of seven grafts survived long term >100 days). PTD-dnTLR4-treated grafts exhibited reduced expression of TNF-α and iNOS and reduced macrophage infiltration posttransplant. The data indicate that PTD-dnTLR4 blocked TLR4 signaling in both macrophages and β cells, and prolonged allograft survival at least in part by suppressing inflammation and macrophage infiltration. This strategy for blocking TLR4 activity has potential utilization in the treatment of diseases where excessive TLR4 activation contributes to the pathologic cellular pathways such as islet transplantation.

Reparixin, a CXCR1/2 inhibitor in islet allotransplantation

ABSTRACTQuality of life in Type 1 diabetic patients may be improved with islet transplantation, but lifelong immunosuppression is required to prevent rejection. Allo-immune response is a key player in graft dysfunction and although the adaptive immune response is well characterized, the effect of the innate immune reaction after transplantation is only recently becoming appreciated. In this study, we address how the innate response affects long-term outcomes in a murine islet allotransplant model. CTLA-4 Ig treatment is known to significantly prolong kidney subcapsular islet allograft survival and enhance glucose tolerance. The combination of CTLA-4 Ig with reparixin, which blocks against inflammatory neutrophil infiltration, yielded no long-term graft survival in an intrahepatic allotransplant model but had similar long-term graft survival in the kidney subcapsular model. Seven days after transplant, serum blood IFN-γ levels were significantly lower in the CTLA-4 Ig with reparixin treatment group compared to controls. IL-12p70 cytokine levels were increased with combination treatment, a positive modulation of the inflammatory response to the allograft. Furthermore, KC GRO, also known as CXCL1, was decreased in serum 7 d after transplant. Histologically, we found that immune cell infiltrate, CD4+ and CD8+ T cell populations along with both CXCR1+ and CXCR2+ cell populations were decreased within the CTLA-4 Ig and reparixin islet transplant graft. Overall these data provide insight into the down regulation of T-cell recruitment by CTLA-4 Ig and decreased neutrophil activation and recruitment with reparixin after long-term islet graft survival.

COMP-Ang1 promotes long-term survival of allogeneic islet grafts in a bioinert perforated chamber by inhibiting inflammation via inhibition of the TLR4 signaling pathway.

To evaluate the effects of cartilage oligomeric matrix protein (COMP)- angiopoietin-1 (Ang1) on allogeneic islet graft survival in a bioinert perforated chamber. COMP-Ang1 treatment significantly decreased lipopolysaccharide-induced cell apoptosis and islet-related lymph node cell proliferation (both P<0.01). Tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 levels in the chamber exudate were significantly lower in the COMP-Ang1+chamber group than in the chamber group (all P<0.05), as were the protein expression levels. COMP-Ang1 significantly inhibited the expression of Toll-like receptor 4 (TLR4) in cultured islets. Finally, full COMP-Ang1 treatment resulted in the longest survival time among the treatment groups. Combined use of the bioinert perforated chamber with COMP-Ang1 is an effective strategy for improving islet allograft survival.

B Cell Depletion With an Anti-CD20 Antibody Enhances Alloreactive Memory T Cell Responses After Transplantation

Alloreactive memory T cells mediate accelerated allograft rejection and transplant tolerance resistance. Recent studies have shown that B cell deficient-μMT mice fail to mount donor-specific memory T cell responses after transplantation. At the same time, other studies showed that pretransplant B cell depletion using rituximab (IgG1 anti-CD20 mAb) combined with cyclosporine A promoted the survival of islet allografts in monkeys. In this study, we investigated the effect of anti-CD20 antibody-mediated B cell depletion on the memory T cell alloresponse in mice. Wild-type and anti-OVA TCR transgenic mice were treated with an IgG2a anti-CD20 monoclonal antibody, which depleted nearly all B cells in the peripheral blood and secondary lymphoid organs but spared some B cells in the bone marrow. B cell depletion did not affect the direct alloresponse but resulted in a marked increase of indirect alloresponse after skin transplantation of naïve mice. Furthermore, in allosensitized mice, anti-CD20 mAb treatment enhanced the reactivation of allospecific memory T cells and accelerated second set rejection of skin allografts. This suggests that the effect of anti-CD20 antibodies on alloimmunity and allograft rejection might vary upon the nature of the antibodies as well as the circumstances under which they are delivered.

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.

Arsenic Trioxide Induces T Cell Apoptosis and Prolongs Islet Allograft Survival in Mice.

T cell-mediated immune rejection is a key barrier to islet transplantation. Preliminary studies have shown that arsenic trioxide (As2O3) can inhibit T cell responses and prolong heart allograft survival. Here, we sought to investigate the possibility of using As2O3 to prolong islet allograft survival in an acute rejection model of Balb/c to C57B/6 mice. Recipient mice were treated with As2O3 and/or rapamycin after islet allograft transplantation. At day 10 after transplantation, the graft, spleen, lymph nodes, and blood of the recipient mice were recovered for analysis. In vitro, to further examine the mechanism underlying As2O3 protection of islet allografts against T cell-mediated rejection, mixed lymphocyte reaction and apoptosis analyses of T cells were performed. The phosphorylation levels of IκBα and p38 were also evaluated to confirm the proliferation and apoptosis of As2O3-treated T cells. We found that As2O3 prolonged islet allograft survival by reducing inflammatory reactions, influencing cytokine synthesis and secretion and T-cell subset proportions, and inhibiting T-cell responses. Furthermore, As2O3 and rapamycin showed a synergistic effect in suppressing islet allotransplant rejection. Arsenic trioxide may prevent allograft rejection by inhibiting T-cell proliferation and inducing T-cell apoptosis.

Induction of tolerance and prolongation of islet allograft survival by syngeneic hematopoietic stem cell transplantation in mice

BackgroundsSyngeneic or autologous hematopoietic stem cells transplantation (HSCT) has been proposed to treat autoimmune diseases because of its immunosuppressive and immunomodulatory effects, which can also contribute to posttransplant antirejection therapy. In this study, we explored the tolerogenic effect of syngeneic HSCT on prolonging islet allograft survival. MethodsC57BL/6 mice received syngeneic HSCT plus preconditioning with sublethal irradiation. Then islets of BALB/c mice were transplanted into the renal subcapsular of C57BL/6 mice after chemically induced into diabetes. ResultsHSCT mice exhibited improved islet allograft survival and increased serum insulin compared to control mice. Islet allografts of HSCT mice displayed lower level lymphocyte infiltration and stronger insulin staining than control mice. T cells of HSCT mice proliferated poorly in response to allogeneic splenocytes compared to control mice. Mice appeared reversed interferon-γ (IFN-γ)/interleukin-4 (IL-4) ratio to a Th2 immune deviation after syngeneic HSCT. The percentage of CD8+ T cells was lower, while percentage of CD4+CD25+Foxp3+ T regulatory cells (Tregs) was higher in HSCT mice than control mice. HSCT mice showed higher percentage of CTLA-4+ T cells and expression of CTLA-4 mRNA than control mice. Targeting of CTLA-4 by intraperitoneal injection of anti-CTLA-4 mAb abrogated the effect of syngeneic HSCT on prolonging islet allograft survival, inhibiting activity of T cells in response to alloantigen, promoting Th1 to Th2 immune deviation and up regulating CD4+CD25+Foxp3+ Tregs. ConclusionsSyngeneic HSCT plus preconditioning of sublethal irradiation induces tolerance and improves islet allograft survival in fully mismatched mice model. Th1 to Th2 immune deviation, increased CD4+CD25+Foxp3+ Tregs and up-regulation of CTLA-4 maybe contribute to the tolerogenic effect induced by syngeneic HSCT.