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The healthy exocrine pancreas contains preproinsulin-specific CD8 T cells that attack islets in type 1 diabetes.

ABSTRACT: Preproinsulin (PPI) is presumably a crucial islet autoantigen found in patients with type 1 diabetes (T1D) but is also recognized by CD8+ T cells from healthy individuals. We quantified PPI-specific CD8+ T cells within different areas of the human pancreas from nondiabetic controls, autoantibody-positive donors, and donors with T1D to investigate their role in diabetes development. This spatial cellular quantitation revealed unusually high frequencies of autoreactive CD8+ T cells supporting the hypothesis that PPI is indeed a key autoantigen. To our surprise, PPI-specific CD8+ T cells were already abundantly present in the nondiabetic pancreas, thus questioning the dogma that T1D is caused by defective thymic deletion or systemic immune dysregulation. During T1D development, these cells accumulated in and around islets, indicating that an islet-specific trigger such as up-regulation of major histocompatibility complex class I might be essential to unmask beta cells to the immune system.

SUBMITTER: Bender C

PROVIDER: S-EPMC7567597 | biostudies-literature | 2020 Oct

REPOSITORIES: biostudies-literature

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The healthy exocrine pancreas contains preproinsulin-specific CD8 T cells that attack islets in type 1 diabetes.

Bender Christine C Rodriguez-Calvo Teresa T Amirian Natalie N Coppieters Ken T KT von Herrath Matthias G MG

Science advances 20201016 42

Preproinsulin (PPI) is presumably a crucial islet autoantigen found in patients with type 1 diabetes (T1D) but is also recognized by CD8<sup>+</sup> T cells from healthy individuals. We quantified PPI-specific CD8<sup>+</sup> T cells within different areas of the human pancreas from nondiabetic controls, autoantibody-positive donors, and donors with T1D to investigate their role in diabetes development. This spatial cellular quantitation revealed unusually high frequencies of autoreactive CD8<su ...[more]

PMID: 33067232

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Project description:Coinhibitory PD-1/PD-L1 (B7-H1) interactions provide critical signals for the regulation of autoreactive T-cell responses. We established mouse models, expressing the costimulator molecule B7.1 (CD80) on pancreatic beta cells (RIP-B7.1 tg mice) or are deficient in coinhibitory PD-L1 or PD-1 molecules (PD-L1(-/-) and PD-1(-/-) mice), to study induction of preproinsulin (ppins)-specific CD8 T-cell responses and experimental autoimmune diabetes (EAD) by DNA-based immunization. RIP-B7.1 tg mice allowed us to identify two CD8 T-cell specificities: pCI/ppins DNA exclusively induced K(b)/A(12-21)-specific CD8 T-cells and EAD, whereas pCI/ppinsΔA(12-21) DNA (encoding ppins without the COOH-terminal A(12-21) epitope) elicited K(b)/B(22-29)-specific CD8 T-cells and EAD. Specific expression/processing of mutant ppinsΔA(12-21) (but not ppins) in non-beta cells, targeted by intramuscular DNA-injection, thus facilitated induction of K(b)/B(22-29)-specific CD8 T-cells. The A(12-21) epitope binds K(b) molecules with a very low avidity as compared with B(22-29). Interestingly, immunization of coinhibition-deficient PD-L1(-/-) or PD-1(-/-) mice with pCI/ppins induced K(b)/A(12-21)-monospecific CD8 T-cells and EAD but injections with pCI/ppinsΔA(12-21) did neither recruit K(b)/B(22-29)-specific CD8 T-cells into the pancreatic target tissue nor induce EAD. PpinsΔA(12-21)/(K(b)/B(22-29))-mediated EAD was efficiently restored in RIP-B7.1(+)/PD-L1(-/-) mice, differing from PD-L1(-/-) mice only in the tg B7.1 expression in beta cells. Alternatively, an ongoing beta cell destruction and tissue inflammation, initiated by ppins/(K(b)/A(12-21))-specific CD8 T-cells in pCI/ppins+pCI/ppinsΔA(12-21) co-immunized PD-L1(-/-) mice, facilitated the expansion of ppinsΔA(12-21)/(K(b)/B(22-29))-specific CD8 T-cells. CD8 T-cells specific for the high-affinity K(b)/B(22-29)- (but not the low-affinity K(b)/A(12-21))-epitope thus require stimulatory help from beta cells or inflamed islets to expand in PD-L1-deficient mice. The new PD-1/PD-L1 diabetes models may be valuable tools to study under well controlled experimental conditions distinct hierarchies of autoreactive CD8 T-cell responses, which trigger the initial steps of beta cell destruction or emerge during the pathogenic progression of EAD.

Project description:Although type 1 diabetes (T1D) is primarily a disease of the pancreatic beta-cells, understanding of the disease-associated alterations in the whole pancreas could be important for the improved treatment or the prevention of the disease. We have characterized the whole-pancreas gene expression of patients with recently diagnosed T1D from the Diabetes Virus Detection (DiViD) study and non-diabetic controls. Furthermore, another parallel dataset of the whole pancreas and an additional dataset from the laser-captured pancreatic islets of the DiViD patients and non-diabetic organ donors were analyzed together with the original dataset to confirm the results and to get further insights into the potential disease-associated differences between the exocrine and the endocrine pancreas. First, higher expression of the core acinar cell genes, encoding for digestive enzymes, was detected in the whole pancreas of the DiViD patients when compared to non-diabetic controls. Second, In the pancreatic islets, upregulation of immune and inflammation related genes was observed in the DiViD patients when compared to non-diabetic controls, in line with earlier publications, while an opposite trend was observed for several immune and inflammation related genes at the whole pancreas tissue level. Third, strong downregulation of the regenerating gene family (REG) genes, linked to pancreatic islet growth and regeneration, was observed in the exocrine acinar cell dominated whole-pancreas data of the DiViD patients when compared with the non-diabetic controls. Fourth, analysis of unique features in the transcriptomes of each DiViD patient compared with the other DiViD patients, revealed elevated expression of central antiviral immune response genes in the whole-pancreas samples, but not in the pancreatic islets, of one DiViD patient. This difference in the extent of antiviral gene expression suggests different statuses of infection in the pancreas at the time of sampling between the DiViD patients, who were all enterovirus VP1+ in the islets by immunohistochemistry based on earlier studies. The observed features, indicating differences in the function, status and interplay between the exocrine and the endocrine pancreas of recent onset T1D patients, highlight the importance of studying both compartments for better understanding of the molecular mechanisms of T1D.

Dataset Information

The healthy exocrine pancreas contains preproinsulin-specific CD8 T cells that attack islets in type 1 diabetes.

Publications

The healthy exocrine pancreas contains preproinsulin-specific CD8 T cells that attack islets in type 1 diabetes.

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