Diabetes is a set of chronic diseases characterized by hyperglycemia and pancreatic dysfunction. The pancreas consists of two tissue compartments with highly distinct functions – hormone-producing islets of Langerhans and acinar tissue with an exocrine function. Improved understanding of immune processes and stromal cells within the compartments of the pancreas may highlight important specializations, which could lead to novel insights into islet dysfunction in diabetes or islet transplantation. Thus, in this thesis the properties of pancreatic innate immunity and microvascular endothelial cells were compared between islet- and exocrine tissue from human organ donors. 

Enteroviral infection has been suggested to trigger development of type 1 diabetes. In paper I, the feasibility of using innate immunity viral sensor protein kinase R (PKR) as evidence of enteroviral infection in the pancreas was examined. A general PKR expression was found at protein and RNA level in islets and exocrine tissue under basal conditions, and in vitro infection of islets with enterovirus did not lead to distinct PKR expression. This suggests that PKR expression should not be used to corroborate enteroviral infection in the human pancreas. In paper II, gene expression profiles were generated and compared between microvascular endothelial cells (MVECs) from islets and exocrine tissue. Gene sets involved in vascular- and endothelial development were enriched in islet MVEC samples. This suggests increased vascular proliferation within islets, potentially consistent with tissue remodeling. In paper III, gene expression profiles were generated and analyzed in CD206- and CD206+ macrophages from islets and exocrine tissue. Gene sets involved in inflammation and glycolysis were enriched in CD206- macrophages, while gene sets involved in complement, scavenging and immune regulation were enriched in CD206+ macrophages. In comparisons between tissues, a few immune regulation-associated gene sets were enriched in islet macrophages while gene sets associated with proinflammatory functions and extracellular matrix were enriched in exocrine macrophages. 

The main findings in this thesis were that expression of PKR is poor evidence of viral infection in the pancreas, identification of islet-MVEC gene expression consistent with intraislet vascular remodeling, and a characterization of global gene expression in two subgroups of macrophages in islets and in exocrine tissue.