Autoimmune Rejection Research Articles

Beta cell expression of ST8Sia6 protects from autoimmune diabetes in the murine NOD model

Abstract In this study, we leveraged immunomodulatory Siglec-sialic acid interactions to protect beta-cells against autoimmune rejection in Type 1 Diabetes (T1D). Our lab previously demonstrated that the sialyltransferase ST8Sia6 generates ligands that bind the Siglec-E receptor expressed on murine islet-resident macrophages. Here, mice were engineered to express ST8Sia6 in beta cells (βST mice), backcrossed to the non-obese diabetic (NOD) mouse model of T1D, and followed for disease. 60% of female littermates spontaneously developed disease by 300 days, compared to only 6% in female βST mice. Histologic analysis of pancreas sections from non-diabetic βST and littermate mice suggested a similar degree of immune infiltration in early life, but drastically reduced insulitis only in βST mice at later timepoints. This was not due to an absence of autoreactive T cells, as an anti-PD-L1 challenge resulted in similarly rapid induction of disease in both βST and littermate mice. Our genetic model allows for temporal control of ST8Sia6 expression in βST mice using the tet-off system. Treating our mice with doxycycline at 20 weeks of age resulted in persistent protection compared to age matched littermates, while the same treatment at 8 weeks of age led to similar incidence of diabetes between βST mice and littermate controls. Flow cytometric analysis of islet infiltrating immune cells from euglycemic mice at 14 weeks of age demonstrated reductions in short-lived effector CD8 T cells and increased thymically derived Tregs in βST mice compared to littermate controls. These results highlight the therapeutic potential of sialyltransferase mediated immune regulation and present a potential path toward improved curative approaches for T1D. Supported by grants from NIH (5R21AI135858-02, 1F30DK127564)

ST8Sia6 expression in beta cells mitigates onset of autoimmune diabetes in the murine NOD model

Abstract In this study, we harnessed immunomodulatory Siglec-sialic acid interactions to mitigate autoimmune rejection of beta cells in Type 1 Diabetes (T1D). Mice engineered to express the sialyltransferase ST8Sia6 in beta cells (βST mice) were backcrossed to the non-obese diabetic mouse model of T1D and followed for disease; 60% of female littermates spontaneously developed diabetes by 300 days, compared to minimal occurrence (5%) in female βST mice. Histologic analysis of pancreas sections from non-diabetic βST and littermate mice suggested a similar degree of immune infiltration at 4 and 8 weeks of age, but the severity of insulitis was drastically reduced in βST mice beyond 20 weeks of age as compared to littermates. IHC for various immune populations suggested no difference in composition of insulitis at 8 weeks between βST and littermate mice. ELISA for serum anti-insulin antibodies demonstrated no difference in concentration between female βST and littermate mice. After female euglycemic βST and littermate mice at 16 weeks of age were challenged with anti-PD-L1 monoclonal antibodies, both groups resulted in similarly rapid induction of disease, suggesting that ST8Sia6 dependent protection occurs peripherally. Shut-off of ST8Sia6 expression in euglycemic βST mice at 20 weeks of age did not abrogate protection from disease, supporting persistent immune tolerance beyond this time. Flow analysis of islet infiltrating immune cells at 300 days confirmed reduced number of infiltrating immune cells in βST mice. Thus, induced expression of ST8Sia6 has been shown to mitigate autoimmune attack in the NOD mouse and presents a novel path forward for improving the success of curative islet transplant into T1D patients. Supported by funding from the Mayo Clinic (Mayo Clinic Center for Biomedical Discovery, Mayo Clinic Graduate School of Biomedical Sciences, Mayo Clinic MSTP) and the NIH (5R21AI135858-02, 1F30DK127564). Supported by funding from the Mayo Clinic (Mayo Clinic Center for Biomedical Discovery, Mayo Clinic Graduate School of Biomedical Sciences, Mayo Clinic MSTP) and the NIH (5R21AI135858-02, 1F30DK127564).

Treatment of sinus membrane perforations during sinus lift surgeries using leukocyte and platelet-rich fibrin: A report of three cases

Schneiderian membrane (SM) perforation is the most frequent intraoperative complication during sinus lifts, which can lead to implant failure or delayed implant treatment. This article aims to show the results of using leukocyte and platelet-rich fibrin (L-PRF) in the treatment of perforations occurring during sinus lifts with a lateral window approach. Three patients (n = 5 implants) with a mean ± SD age of 57.67 ± 12.12 years were included, in whom perforations of the SM of 3-5 mm and >5 mm occurred. The mean ± SD preoperative bone height was 4.42 ± 2.96 and, at 6 months it was 9.58 ± 2.41 (P < 0.05). All implants had a 100% survival rate at 6-24 months. At the split-mouth, the mean ± SD baseline height was 5.05 ± 2.99 mm in repaired SM versus 2.92 ± 1.01 in those without any complications (P > 0.05). At 6 months, mean ± SD gains were 10.09 ± 2.44 mm versus 7.73 ± 0.90 mm, respectively, (P > 0.05). L-PRF simplifies SM repair, reducing the need for high surgical experience and/or skills. Although there are no significant differences between repaired and intact SM, at the radiological level, greater bone compactness and maturation were observed in the latter, which may be associated with the presence of air bubbles caused by anaerobic bacterial activity in repaired SM. The use of L-PRF greatly simplifies the resolution of SM perforations during sinus lift surgeries, reducing treatment times, and providing predictable results. Being of autologous origin, it accelerates and enhances healing, eliminating the possibility of autoimmune rejection reactions.

TRANSPLANTATION OF GOLD NANOPARTICLES WITH OR WITHOUT BONE MARROW STEM CELLS FOR REGENERATION OF SURGICALLY INDUCED TONGUE DEFECT IN RATS

The ultimate goal of tongue reconstruction is restoring the tongue integrity while preserve its critical functions(i.e., articulation, mastication, and deglutition) and minimize the morbidity profile of a selected reconstructive technique. Mesenchymal stem cells (MSCs) used in tissue engineering became a therapeutic selectiondue to numerous advantagesas regeneration of damaged tissues withhigh quality without the formation of fibrous tissue, minimal donor site morbidity in comparison withautografts and a low risk ofdisease transmition and autoimmune rejection. Bone marrow stem cells (BMSCs) areexpandable stem, self-renewing,embedded at the site of injury and motivate tissue regeneration and wound healing. In oral wounds, they revealgreater re-epithelialization, intracellular matrix formation,cellularity, and neoangiogenesis, thusspeed up wound healing.Gold nanoparticles (GNPs) application in medical fields is growingdue to the chemical and physical properties like biocompatibility, optical properties,facile surface modification and stability.GNP usage in regenerative medicine is safe if the implanted tissue is replacing a tissue/organresectedbecause of tumor.

P.159: Investigating the Role of Cathepsin L in Islet Graft Rejection

Type 1 diabetes (T1D) is a T cell-mediated autoimmune disorder in which beta-cell specific destruction leads to life-long exogenous insulin dependence. While islet transplantation can restore euglycemia in these patients, both allogeneic and autoimmune rejection of the islet graft pose challenges limiting graft longevity. CD4+ T cells play a major role in driving T1D autoimmune development and islet graft rejection. Recent discovery of hybrid insulin peptides (HIPs), a fusion of insulin peptides with other beta-cell granule containing peptides, were found to be cognate autoantigens for autoreactive CD4+ T cells in mouse models and in patients with T1D. HIPs are formed within the beta-cell during crinophagy, a process of protein degradation or turnover where insulin granules fuse with lysosomes. By reducing the formation of HIPs, autoimmune-mediated islet graft rejection may be delayed. Cathepsin L (CatL) is a lysosomal endopeptidase enzyme involved in protein degradation and is implicated in the generation of HIPs. Non-Obese Diabetic (NOD) mice lacking CatL (NOD.CatL-/-) exhibited a delay in spontaneous T1D development. Immunophenotyping of islet-infiltrating immune cells from NOD.CatL-/- mice displayed reductions in effector CD4+ T cells and tetramer-specific autoreactive BDC-2.5, BDC-6.9, and insulin T cells compared to NOD mice. We hypothesize that islets deficient in CatL will delay immune-mediated rejection due to the absence of antigenic HIPs following transplantation. CatL-deficient islets may improve islet graft survival due to reduced release of antigenic peptides and passenger CD4+ T cells when transplanted into recipient mice. Isolated islets (250 islets/recipient) from NOD.CatL-/-, NOD.CatL+/-, or NOD.Rag mice, were transplanted under the kidney capsule of streptozotocin-treated and spontaneously diabetic NOD mice and monitored for restoration and maintenance of euglycemia. Both NOD.CatL-/- and NOD.CatL+/- islets restored euglycemia similarly as NOD.Rag islets. Future studies will investigate the impact of CatL-deficiency on long-term graft survival and effects on immune cell infiltration and activation. This work was supported by an NIH/NIDDK R01 award (DK099550), JDRF award SRA-2016-270-S-B, JDRF award 2-SRA-2019-692-S-B, NIH/NIDDK R01 award (DK126456), NIH/NIDDK R01 award (DK127497), NIH/NIGMS (T32GM008111) Cell, Molecular, and Developmental Biology T32 training grant.

Immune Protection of Stem Cell-Derived Islet Cell Therapy for Treating Diabetes.

Insulin injection is currently the main therapy for type 1 diabetes (T1D) or late stage of severe type 2 diabetes (T2D). Human pancreatic islet transplantation confers a significant improvement in glycemic control and prevents life-threatening severe hypoglycemia in T1D patients. However, the shortage of cadaveric human islets limits their therapeutic potential. In addition, chronic immunosuppression, which is required to avoid rejection of transplanted islets, is associated with severe complications, such as an increased risk of malignancies and infections. Thus, there is a significant need for novel approaches to the large-scale generation of functional human islets protected from autoimmune rejection in order to ensure durable graft acceptance without immunosuppression. An important step in addressing this need is to strengthen our understanding of transplant immune tolerance mechanisms for both graft rejection and autoimmune rejection. Engineering of functional human pancreatic islets that can avoid attacks from host immune cells would provide an alternative safe resource for transplantation therapy. Human pluripotent stem cells (hPSCs) offer a potentially limitless supply of cells because of their self-renewal ability and pluripotency. Therefore, studying immune tolerance induction in hPSC-derived human pancreatic islets will directly contribute toward the goal of generating a functional cure for insulin-dependent diabetes. In this review, we will discuss the current progress in the immune protection of stem cell-derived islet cell therapy for treating diabetes.

Valproic Acid Suppresses Autoimmune Recurrence and Allograft Rejection in Islet Transplantation through Induction of the Differentiation of Regulatory T Cells and Can Be Used in Cell Therapy for Type 1 Diabetes.

Type 1 diabetes mellitus (T1D) results from the destruction of insulin-producing β cells in the islet of the pancreas by lymphocytes. Non-obese diabetic (NOD) mouse is an animal model frequently used for this disease. It has been considered that T1D is a T cell-mediated autoimmune disease. Both CD4+ and CD8+ T cells are highly responsible for the destruction of β cells within the pancreatic islets of Langerhans. Previous studies have revealed that regulatory T (Treg) cells play a critical role in the homeostasis of the immune system as well as immune tolerance to autoantigens, thereby preventing autoimmunity. Valproic acid (VPA), a branched short-chain fatty acid, is widely used as an antiepileptic drug and a mood stabilizer. Previous reports have demonstrated that VPA treatment decreases the incidence and severity of collagen-induced arthritis and experimental autoimmune neuritis by increasing the population of Treg cells in these mouse disease models. Given the effect of VPA in the induction of Treg cells’ population, we evaluated the therapeutic potential and the protective mechanism of VPA treatment in the suppression of graft autoimmune rejection and immune recurrence in syngeneic or allogenic islet transplantation mouse models. In our study, we found that the treatment of VPA increased the expression of forkhead box P3 (FOXP3), which is a critical transcription factor that controls Treg cells’ development and function. Our data revealed that 400 mg/kg VPA treatment in recipients effectively prolonged the survival of syngeneic and allogenic islet grafts. The percentage of Treg cells in splenocytes increased in VPA-treated recipients. We also proved that adoptive transfer of VPA-induced Tregs to the transplanted recipients effectively prolonged the survival of islet grafts. The results of this study provide evidence of the therapeutic potential and the underlying mechanism of VPA treatment in syngeneic islet transplantation for T1D. It also provides experimental evidence for cell therapy by adoptive transferring of in vitro VPA-induced Tregs for the suppression of autoimmune recurrence.

ST8Sia6 expression in beta cells mitigates onset of autoimmune diabetes in the murine NOD model

Abstract Cell surface hypersialylation is used by malignant cells as a survival mechanism, leveraging interactions with inhibitory Siglec receptors to dampen immune rejection. In this study, we harnessed this mechanism to prevent autoimmune rejection of beta cells in the context of Type 1 Diabetes. Mice were engineered to express the sialyltransferase ST8Sia6 in a beta cell specific manner (βST mice) and crossed to the non-obese diabetic (NOD) mouse model of spontaneous autoimmune diabetes. Both female and male littermates on the NOD background developed diabetes by 300 days (56% and 80.8%, respectively). βST mice, however, demonstrated minimal occurrence of disease (5.3% and 16.6%). Additionally, histologic analysis of pancreas sections from non-diabetic βST and littermate mice suggested a similar degree of immune infiltration at 4 and 8 weeks of age, but the severity of infiltration was drastically reduced only in the βST mice at 20 weeks of age. IHC for various leukocyte markers suggested no difference in composition of immune infiltrates at the 8 week time point. To determine whether protection was due to central or peripheral mechanisms, euglycemic βST and littermate mice at 16 weeks of age were challenged with anti-PD-L1 monoclonal antibodies; both groups resulted in similar induction of disease, suggesting that ST8Sia6 dependent protection occurs peripherally. Physiologically, an insulin tolerance test demonstrated no difference between βST mice and littermates, suggesting no systemic effects of beta cell ST8Sia6 expression. The induced expression of ST8Sia6 has been shown to mitigate autoimmune attack in the NOD mouse and presents a novel path forward for improving the success of curative islet transplant into diabetic patients.

ST8Sia6 overexpression in beta cells prevents onset of autoimmune diabetes in the murine NOD model

Abstract Cell surface hypersialylation is used by malignant cells as a survival mechanism, leveraging interactions with Siglec receptors to dampen the immune response. In this study, we aimed to harness this mechanism to prevent autoimmune rejection of beta cells in the context of type 1 diabetes. Mice engineered to overexpress the sialyltransferase ST8Sia6 in beta cell (BST) were generated and crossed to the non-obese diabetic (NOD) mouse for 10 generations. The blood glucose of these mice compared to non-overexpressing littermates was assessed twice weekly to determine diabetes incidence, defined as 3 consecutive blood glucose readings above 250 mg/dL. Analysis of female BST mice aged 15 weeks or greater showed no incidence of overt diabetes, while littermates developed diabetes. BST males aged 15 weeks or greater also had no disease incidence, while littermate controls also became diabetic. An insulin tolerance test demonstrated no significant difference between BST mice and littermates, though the BST had significantly higher blood glucose during a glucose challenge, possibly representing insulin hypersecretion by littermate islets in a stressed pre-diabetic state. Histologic analysis of young BST and littermate pancreata showed no differences, with similar levels of insulitis at 8 weeks. Thus, the overexpression of ST8Sia6 has been shown to mitigate autoimmune attack in the NOD model and presents a novel path forward for prevention of islet transplant rejection.

Phenytoin/sildenafil loaded poly(lactic acid) bilayer nanofibrous scaffolds for efficient orthopedics regeneration

Autologous and synthetic bone grafts showed some limitations during their usage in bone tissue regeneration. This is attributed to several drawbacks such as difficulty of finding a donor in addition to the autoimmune rejection. This study aims to fabricate a well-designed biocompatible double-layered structure of highly porous poly(lactic acid)-based electrospun nanofibers (NFs) as scaffolds for bone tissue regeneration. Poly(lactic acid) was chosen to fabricate the main matrix of the NFs scaffold as it is one of the FDA approved and highly recommended biopolymers for biomedical applications owing to its high biodegradability and biocompatibility Each layer is loaded with a different drug (Phenytoin and Sildenafil) to stimulate bone healing process. The solvents and the parameters of electrospinning were manipulated to produce highly porous structures in order to enhance the in-situ biodegradability of the NFs mats as well as the drug release rate. The produced NFs mats were fully characterized morphologically (SEM), chemically (FTIR), physically (DSC) and physicochemically (biodegradability, swellability, porosity and water vapor permeability) as well as studying the drug release profiles of both drugs. Cytotoxicity of the fabricated NFs was tested using fibroblast cells to detect their biocompatibility. Cell adhesion and proliferation were examined using SEM before using the NFs as scaffolds in mice animal model. The efficiency of the developed NFs scaffolds in healing bone fractures was assessed after 14 and 28 days through visual inspection, SEM investigation and bone mineral density assessment. Finally, sections from the bone fracture sites were isolated for histopathological examination. The study revealed the efficiency of the drugs-loaded NFs in enhancing cell adherence, cell proliferation, angiogenesis formation and finally tissue restoration of bone fractures.

Initial Clinical Evaluation of VC-01TM Combination Product—A Stem Cell–Derived Islet Replacement for Type 1 Diabetes (T1D)

VC-01 is a novel cell replacement therapy being developed as a potential long-term diabetes therapy to more effectively control glycemia, reduce hypoglycemia risk and mitigate diabetes-related complications. VC-01 is derived from directed differentiation of human embryonic stem cells to pancreatic progenitor cells, which are loaded into a durable, retrievable delivery device and then implanted subcutaneously. Once implanted and matured, the cells secrete insulin and other islet hormones in response to blood glucose levels. The delivery device is immunoprotective to implanted cells. VC-01 is currently being evaluated in a 24-month open-label, dose-escalating Phase 1/2 study in T1D patients with minimal insulin-producing β-cell function. Cohort 1 has evaluated product at a subtherapeutic dose to assess initial safety and tolerability and establish implantation techniques. To date, 19 subjects have been implanted and evaluated throughout implantation duration until final product explant. Product has been safe and well tolerated; adverse events have been relatively minor and generally related to the surgical procedure. The delivery device has provided protection against the host adaptive immune system with no evidence of allogeneic or autoimmune rejection or sensitization based upon a sensitive panel of immune function tests. No off-target growth of donor cells has been detected. The potential for prolonged cell survival has been demonstrated, as long as 24 months, but has been inconsistent among subjects and primarily limited by a foreign body response to the device component. Positive immunohistochemical staining for pancreatic islet cell markers NKX6-1, insulin, and glucagon has been observed. These preliminary results demonstrate the immune-protective nature of the encapsulation device and safety of this human stem cell-derived product, but also indicate the ongoing requirement for optimization of the host response to device materials. Disclosure R.R. Henry: Consultant; Self; Abbott, Alere Inc., AstraZeneca. Research Support; Self; AstaReal. Advisory Panel; Self; Boehringer Ingelheim Pharmaceuticals, Inc.. Consultant; Self; Bristol-Myers Squibb Company. Advisory Panel; Self; Elcelyx Therapeutics, Inc.. Research Support; Self; Eli Lilly and Company, Hitachi, Ltd.. Advisory Panel; Self; AstraZeneca. Consultant; Self; Boehringer Ingelheim Pharmaceuticals, Inc.. Advisory Panel; Self; Intarcia Therapeutics, Inc.. Consultant; Self; Intarcia Therapeutics, Inc., Ionis Pharmaceuticals, Inc., Janssen Pharmaceuticals, Inc.. Advisory Panel; Self; Johnson &amp; Johnson Services, Inc.. Research Support; Self; Lexicon Pharmaceuticals, Inc.. Consultant; Self; Ligand Pharmaceuticals, Inc.. Advisory Panel; Self; Merck &amp; Co., Inc.. Consultant; Self; Merck &amp; Co., Inc.. Research Support; Self; Viacyte, Inc.. Consultant; Self; Sanofi-Aventis. Advisory Panel; Self; Sanofi-Aventis. J. Pettus: Advisory Panel; Self; Sanofi, Novo Nordisk Inc.. Consultant; Self; MannKind Corporation. Advisory Panel; Self; Insulet Corporation. Consultant; Self; Senseonics. J. Wilensky: None. A. Shapiro: Consultant; Self; Viacyte, Inc., Protokinetix. P.A. Senior: Consultant; Self; Abbott, AstraZeneca. Research Support; Self; AstraZeneca, Prometic Life Sciences Inc., Novo Nordisk Inc., Sanofi. Consultant; Self; Eli Lilly and Company. Speaker's Bureau; Self; Eli Lilly and Company, Novo Nordisk Inc.. Consultant; Self; Novo Nordisk Inc., Janssen Pharmaceuticals, Inc.. Speaker's Bureau; Self; Janssen Pharmaceuticals, Inc.. Consultant; Self; Boehringer Ingelheim Pharmaceuticals, Inc.. Speaker's Bureau; Self; AstraZeneca, Merck &amp; Co., Inc., Abbott. Research Support; Self; Viacyte, Inc. B. Roep: Consultant; Self; Viacyte, Inc.. Research Support; Self; Viacyte, Inc. R. Wang: Employee; Self; Viacyte, Inc.. Stock/Shareholder; Self; Sanofi. E.J. Kroon: Employee; Self; Viacyte, Inc. M. Scott: Stock/Shareholder; Self; Viacyte, Inc.. K. D'Amour: None. H.L. Foyt: Employee; Self; Viacyte, Inc.. Stock/Shareholder; Self; Viacyte, Inc..

Microsurgical anastomosis of renal vasculature in rats: A practical platform for acellular kidney transplantation

End-stage renal disease is becoming a contemporary global concern with increasing prevalence. The available treatment strategies are limited to dialysis and renal transplantation. However, limited organ supply and autoimmune rejection are the shortcomings that limit widespread application of transplantation. Favorably, regenerative medicine is able to provide acellular natural scaffolds for renal transplantation. Experimental surgeries in animal models are a fundamental step in transplantation research. This video presents a practical method for transplantation of bilateral acellular kidneys in a rat model, which could serve as a key step for further research.

Mesenchymal stem cells from the oral cavity and their potential value in tissue engineering.

Periodontal disease is one of the most common conditions affecting humans, and current treatment strategies, which focus on the removal and long-term control of dental plaque, are generally successful in eliminating active disease and promoting tissue repair. However, regeneration of the supporting structures of the tooth remains an elusive goal and a challenge. The formation of new bone and cementum with supportive periodontal ligament is the ultimate objective, but current regeneration therapies are incapable of achieving this in a predictable way. The regeneration of periodontal tissue requires a combination of fundamental events, such as appropriate level and sequencing of regulatory signals, the presence of progenitor cells, an extracellular matrix or carrier and an adequate blood supply. Based on tissue-engineering concepts, the regeneration process may be modulated by manipulating the signaling pathways of regulatory molecules, the extracellular matrix or scaffold, or the cellular components. The identification of mesenchymal stem cells from bone marrow started a new era in regenerative medicine. Tissue engineering using mesenchymal stem cells became a therapeutic option with several advantages, including high-quality regeneration of damaged tissues without the formation of fibrous tissue, minimal donor-site morbidity compared with autografts and a low risk of autoimmune rejection and disease transmission. The aim of this review was to describe the main sources of mesenchymal stem cells from tissues in the oral cavity and the potential of these cells in regenerative therapy. Special attention is paid to gingival tissue-derived mesenchymal stem cells because they represent the most accessible source of stem cells in the human mouth.

Autoreactive Effector/Memory CD4+ and CD8+ T Cells Infiltrating Grafted and Endogenous Islets in Diabetic NOD Mice Exhibit Similar T Cell Receptor Usage

Islet transplantation provides a “cure” for type 1 diabetes but is limited in part by recurrent autoimmunity mediated by β cell-specific CD4+ and CD8+ T cells. Insight into the T cell receptor (TCR) repertoire of effector T cells driving recurrent autoimmunity would aid the development of immunotherapies to prevent islet graft rejection. Accordingly, we used a multi-parameter flow cytometry strategy to assess the TCR variable β (Vβ) chain repertoires of T cell subsets involved in autoimmune-mediated rejection of islet grafts in diabetic NOD mouse recipients. Naïve CD4+ and CD8+ T cells exhibited a diverse TCR repertoire, which was similar in all tissues examined in NOD recipients including the pancreas and islet grafts. On the other hand, the effector/memory CD8+ T cell repertoire in the islet graft was dominated by one to four TCR Vβ chains, and specific TCR Vβ chain usage varied from recipient to recipient. Similarly, islet graft- infiltrating effector/memory CD4+ T cells expressed a limited number of prevalent TCR Vβ chains, although generally TCR repertoire diversity was increased compared to effector/memory CD8+ T cells. Strikingly, the majority of NOD recipients showed an increase in TCR Vβ12-bearing effector/memory CD4+ T cells in the islet graft, most of which were proliferating, indicating clonal expansion. Importantly, TCR Vβ usage by effector/memory CD4+ and CD8+ T cells infiltrating the islet graft exhibited greater similarity to the repertoire found in the pancreas as opposed to the draining renal lymph node, pancreatic lymph node, or spleen. Together these results demonstrate that effector/memory CD4+ and CD8+ T cells mediating autoimmune rejection of islet grafts are characterized by restricted TCR Vβ chain usage, and are similar to T cells that drive destruction of the endogenous islets.

Pathogenesis of chagas' disease: parasite persistence and autoimmunity.

Acute Trypanosoma cruzi infections can be asymptomatic, but chronically infected individuals can die of Chagas' disease. The transfer of the parasite mitochondrial kinetoplast DNA (kDNA) minicircle to the genome of chagasic patients can explain the pathogenesis of the disease; in cases of Chagas' disease with evident cardiomyopathy, the kDNA minicircles integrate mainly into retrotransposons at several chromosomes, but the minicircles are also detected in coding regions of genes that regulate cell growth, differentiation, and immune responses. An accurate evaluation of the role played by the genotype alterations in the autoimmune rejection of self-tissues in Chagas' disease is achieved with the cross-kingdom chicken model system, which is refractory to T. cruzi infections. The inoculation of T. cruzi into embryonated eggs prior to incubation generates parasite-free chicks, which retain the kDNA minicircle sequence mainly in the macrochromosome coding genes. Crossbreeding transfers the kDNA mutations to the chicken progeny. The kDNA-mutated chickens develop severe cardiomyopathy in adult life and die of heart failure. The phenotyping of the lesions revealed that cytotoxic CD45, CD8(+) γδ, and CD8α(+) T lymphocytes carry out the rejection of the chicken heart. These results suggest that the inflammatory cardiomyopathy of Chagas' disease is a genetically driven autoimmune disease.

Critical role of IFN-γ in CFA-mediated protection of NOD mice from diabetes development

IFN-gamma signaling-deficient non-obese diabetic (NOD) mice develop diabetes with similar kinetics to those of wild-type NOD mice. However, the immunization of IFN-gamma signaling-deficient NOD mice with CFA failed to induce long-term protection, whereas wild-type NOD mice receiving CFA remained diabetes-free. CFA also failed to protect IFN-gamma receptor-deficient (IFN-gammaR(-/-)) NOD mice from the autoimmune rejection of transplanted islets, as it does in diabetic NOD mice, and from disease transfer by spleen cells from diabetic NOD mice. These data clearly show that the pro-inflammatory cytokine IFN-gamma is necessary for the CFA-mediated protection of NOD mice from diabetes. There is no difference in the T(h)1/T(h)17 balance between IFN-gammaR(-/-) NOD and wild-type NOD mice. There is also no difference in the total numbers and percentages of regulatory T (Treg) cells in the lymph node CD4(+) T-cell populations between IFN-gammaR(-/-) NOD and wild-type NOD mice. However, pathogenic T cells lacking IFN-gammaR are resistant to the suppressive effect of Treg cells, both in vivo and in vitro. Therefore, it is likely that CFA-mediated protection against diabetes development depends on a change in the balance between Treg cells and pathogenic T cells, and IFN-gamma signaling seems to control the susceptibility of pathogenic T cells to the inhibitory activity of Treg cells.

β cell regeneration

Replacing the 350 million β cells destroyed in people with type 1 diabetes has traditionally been sought by transplanting human pancreatic tissue obtained after death. Alternative sources of exogenous surrogate β cells being examined include stem cells, fetal pancreas and cells derived from the liver, with pluripotent stem cells offering the most hope for a large supply of usable tissue. Whilst induced pluripotent stem cells offer the benefit of being autologous, genetic manipulation required for their formation creates safety concerns for future therapeutic use. Encapsulation of pancreatic progenitors derived from embryonic stem cells seems to offer a solution allowing acceptance of the histoincompatible cells, and prevention not only of teratomas but also recurrence of autoimmune rejection. Regenerating β cells from non-β cells in the endogenous pancreas is being attempted using several agents, with most promise ones arising from the administration of gastrin and an incretin. The peptide INGAP, or its humanized version, HIP, also may be beneficial. At present, more benefit has been achieved in rodents, but clinical trials are underway. The main source of new β cells in humans is from pancreatic progenitors, whereas in rodents it is from pre-existing β cells.

Systemic Overexpression of Interleukin-10 Fails to Protect Allogeneic Islet Transplants in Nonobese Diabetic Mice

Interleukin (IL)-10 has proven effective in various allogeneic transplantation models and for preventing recurrent autoimmune rejection of syngeneic islets in NOD mice. Therefore, we evaluated systemic IL-10 overexpression on allogeneic islet graft survival. Diabetic NOD mice received a single injection of recombinant adeno-associated virus (rAAV) serotype 2 encoding murine IL-10 (rAAV-IL-10) four weeks prior to renal subcasular islet transplantation. In a model having both autoimmune and allogeneic responses, IL-10 failed to protect C57BL/6 islets in spontaneously diabetic NOD mice. In an allograft model (C57BL/6 islets into young male streptozotocin-induced diabetic NOD mice), long-term (i.e., >169 days) islet survival was only seen in 2 of 14 rAAV-IL-10 treated mice. These failures occurred despite in vivo IL-10 production at transplant previously associated with protection of syngeneic islet grafts in NOD mice. Thus, IL-10 appears insufficient in protecting transplanted islet cells from allogeneic rejection and suggests important mechanistic variances between alloreactivity and autoimmunity in terms islet graft loss.

Auto-immune-like cone dystrophy

To describe rapid loss of cone vision in an adult due to putative auto-immune rejection. Clinical and electrophysiological examination, including full-field and multi-focal electroretinograms (ERGs), were used to assess retinal function. Serum was analyzed for antibodies to retinal antigens. The patient lost cone vision in the course of several months while rod vision remained unaffected. Initially short wavelength (S) cone function appeared more resistant to the degeneration. Cancer associated retinal antibodies were present in the sera of the patient but no cancer has been found. Rapid loss of cone function can occur in an adult without a concomitant neoplasm although serum antibodies to retinal antigens suggest an autoimmune cause.

"Autoimmune rejection" of neonatal heart transplants in experimental Chagas disease is a parasite-specific response to infected host tissue.

Infection with the protozoan parasite Trypanosoma cruzi often results in chronic heart- and gut-associated disease known as Chagas disease. In this study we show that contrary to previous reports, neonatal hearts transplanted into mice chronically infected with T. cruzi do not exhibit signs of autoimmune-type rejection or any significant inflammatory response. In addition to an absence of inflammation, these syngeneic heart transplants survive for more than 1 year and are absolutely free of parasites as determined by in situ PCR analysis. However, if well-established transplanted hearts in chronically infected mice are directly injected with live parasites, a rapid and dramatic inflammatory response ensues that results in cessation of heart function. Likewise, transplanted hearts established in mice prior to systemic infection with T. cruzi or hearts transplanted into mice during the acute stage of T. cruzi infection become parasitized and develop inflammatory foci. In these cases where the transplanted hearts become parasitized, the ensuing inflammatory response is nearly identical to that observed in the native hearts of T. cruzi-infected mice in terms of cell types present and adhesion molecules and cytokines expressed. Importantly, this response is strikingly different from that observed in the allogeneic heart rejection. These results clearly document that parasitization of heart tissue is both necessary and sufficient for the induction of tissue damage in Chagas disease and strongly argue against a principal autoimmune etiology for this disease.