Six pancreas (two from each region) and one spleen paraffin block from each donor were serially sectioned and stained by hematoxylin and eosin (H&E) and immunohistochemistry. Two double immunohistochemistry stains were used to identify cell replication (Ki67) and β-cells (insulin), or T cell infiltration (CD3) and alpha cells (glucagon) according to published methods (14 (link)). Histopathological review was conducted with an emphasis on islet morphology, size, and numbers, alpha- and β-cell composition, and presence of inflammation (i.e., insulitis, pancreatitis). Insulitis was distinguished by the presence of 6 or more CD3+ cells adjacent to or within an islet. Stained slides were digitized by whole slide scanning using an Aperio CS scanner and were organized by each donor using the Spectrum Plus information management system (version 11, Aperio, Vista, CA). All paraffin blocks from the autoantibody positive donors were reviewed for the presence of insulitis following H&E staining.