Considerations and Challenges of Islet Transplantation and Future Therapies on the Horizon

Islet transplantation is a treatment for selected adults with Type 1 diabetes and severe hypoglycemia. Islets from two or more donor pancreases, a scarce resource, are usually required to impact on glycemic control but the treatment falls short of a cure. Islets are avascular when transplanted into the hypoxic liver environment and subjected to inflammatory insults, immune attack and toxicity from systemic immunosuppression. The Collaborative Islet Transplant Registry with outcome data on over 1000 islet transplant recipients has demonstrated that larger islet numbers transplanted and older age of recipient are associated with better outcomes. Induction with T cell depleting agents and the TNF-α inhibitor Etanercept and maintenance systemic immunosuppression with mTOR inhibitors in combination with calcineurin inhibitors also appear advantageous, but concerns remain over immunosuppressive toxicity. We discuss strategies and therapeutics which address specific challenges of islet transplantation, many of which are at the pre-clinical stage of development. On the horizon are adjuvant cell therapies with mesenchymal stromal cells and regulatory T cells that have been used in preclinical models and in humans in other contexts; such a strategy may enable reductions in immunosuppression in the early peri-transplant period when the islets are vulnerable to apoptosis. Human embryonic stem-cell derived islets are in early phase clinical trials and hold the promise of an inexhaustible supply of insulin producing cells; effective encapsulation of such cells or, silencing of the HLA complex would eliminate the need for immunosuppression, enabling this therapy to be used in all those with Type 1 diabetes.

Digital Gangrene and Pulmonary Consolidation in a Young Girl with Takayasu Arteritis

ABSTRACT Takayasu arteritis is a large-vessel vasculitis most commonly affecting women of childbearing age. The disease process is usually slow and smoldering, presenting over months to years. Digital gangrene is an uncommon manifestation of Takayasu arteritis because of the formation of good collateral circulation. Similarly, although pulmonary artery involvement is well described, pulmonary parenchymal involvement is very rare. We are reporting a case of a young girl with Takayasu arteritis presenting with digital gangrene and pulmonary consolidation, which was treated successfully with a combination of aggressive systemic immunosuppression and anti-coagulants. The possible mechanism for gangrene along with the confounding diagnostic possibility of co-existing tuberculosis have been discussed.

654 Analysis of IDO-1 expression on dendritic cells and factors influencing its up- and downregulation in pancreatic cancer

BackgroundPancreatic Ductal Adenocarcinoma (PDAC) is bad. An immunosuppressive tumor microenvironment (TME) with an excess of immunosuppressive immune cells and cytokine/chemokine factors contribute to local and systemic immunosuppression in PDAC.1 Our laboratory has generated single-cell RNA-Sequencing (scRNA-Seq.) data from spleens derived from PDAC patients and healthy counterparts. This data demonstrates the existence of dendritic cell (DC) subsets with a tolerogenic phenotype. These DCs display increased expression of several markers, including Indoleamine 2,3-dioxygenases (IDO-1 and IDO-2), widely accepted as markers for a specific population of DCs: tolerogenic DCs. These cells evoke an immunosuppressive signal leading to activation of regulatory T cells and MDSCs as well as apoptosis of CD8+ and CD4+ effector T cells.2 3MethodsTo validate our scRNA-Seq. data, we performed pilot investigations harvesting DCs from the spleen of PDAC patients and healthy subjects. Besides examining human specimens, we also investigated the IDO-1 expression on splenic DCs from tumor-bearing mice, orthotopically implanted with LSL-KrasG12D; LSL-Trp53R172H/+; Pdx1-Cre (KPC)-derived cell lines. It is known that tumor-derived exosomes can impact DC-differentiation to a tolerogenic phenotype.4 Exosome purification using differential ultracentrifugation is a well-established method in our lab and optimized for our autopsy samples. We analyzed tumor-derived exosomes for their potential in modulating IDO-1 expression on DCs in in vitro assays. Briefly, we incubated DCs with different exosome concentrations and harvested the cells for RNA-sequencing and flow cytometry.ResultsCompared to normal spleens, DCs from PDAC spleens displayed higher expression of IDO-1 (figure 1). Additionally, KPC-tumor-bearing mice showed higher expression of IDO-1 on DCs from the spleen and blood compared to wild-type mice. Further investigating the influence of PDAC-derived exosomes on marker expression on DCs have shown an apparent increase in expression of IDO-1 when culturing splenic-derived DCs with tumor-derived exosomes (figure 2).ConclusionsWhile tolerogenic DCs are essential in regulating the homeostasis between immune response and immune tolerance,5 several studies have shown IDO-1 overexpression in cancer. Investigating tolerogenic DCs is an essential part of our lab's efforts to understand the nature of the immune response in PDAC. Future directions for this project include determining molecular pathways that regulate the expression of IDO-1. Additionally, we will investigate downstream mechanisms through which exosomes modulate the switch to a tolerogenic phenotype. We also plan to further characterize different splenic DC populations by evaluating their interplay with other immune cells in the context of antigen-specificity and other factors influencing these cells' properties.ReferencesMundry CS, Eberle KC, Singh PK, Hollingsworth MA, Mehla K. Local and systemic immunosuppression in pancreatic cancer: targeting the stalwarts in tumor's arsenal. BBA - Reviews on Cancer 2020;1874(1):188387.Liu M, Wang X, Wang L, Ma X, Gong Z, Zhang S, Li Y. Targeting the IDO1 pathway in cancer: from bench to bedside. Journal of Hematology & Oncology 2018;11(1):100.Hornyák L, Dobos N, Koncz G, Karányi Z, Páll D, Szabó Z, Halmos G, Székvölgyi L. The role of Indoleamine-2,3-Dioxygenase in cancer development, diagnostics, and therapy. Frontiers in immunology 2018;9:1.Bronte V, Pittet MJ. The spleen in local and systemic regulation of immunity. Immunity 2013;39(5):806–818.Domogalla MP, Rostan PV, Raker VK, Steinbrink K. Tolerance through education: how tolerogenic dendritic cells shape immunity. Frontiers in Immunology 2017;8:1764.Ethics ApprovalThis study was approved by the University of Nebraska Medical Center Ethics Board; approval numbers IRB#: 440-16-EP and IRB#: 091-01.Abstract 654 Figure 1Expression of IDO-1 and IDO-2 on DCs from PDAC spleen (blue) .and normal spleen (orange)Abstract 654 Figure 2Change in expression of IDO-1 through treatment of DCs with different concentrations of tumor-derived exosomes

The Liverpool Experience: The Role of Immunosuppression in treating Vasculitic Subglottic Stenosis

Five Key Points • Subglottic stenosis (SGS) is the commonest tracheobronchial manifestation of granulomatosis with polyangiitis (GPA), with early recognition and treatment key to preventing its vasculitic progression and fibrosis. • Previous studies have shown SGS to be the first feature of GPA in 4% of cases. It is not uncommon to see negative biochemical (10% ANCA negative) and negative histological biopsies (77% of head and neck specimens are negative). • Our management strategy emphasized rapid SGS-GPA treatment with limited surgical manipulation of the airway and systemic immunosuppression (IS) to prevent evolution of SGS & concurrent systemic vasculitic relapse. • In our study early multi-disciplinary team involvement to deliver induction IS in the presence of active SGS-GPA led to a procedure free interval (PFI) of 31.3 months. This is a significant increase compared to other published studies. • Nineteen percent (4/21) of the cohort did not require any surgical input following induction IS.