Fig. 1. α-IAPP-O antibody selectively binds to disease-relevant extracellular IAPP aggregates.

a Representative images of pancreas (left panel) and individual pancreatic islets (right panel) from a human type 2 diabetes (T2D) and a non-diabetic control subject stained with mouse chimeric α-IAPP-O (^chα-IAPP-O, 30 nM or at indicated concentrations) and on adjacent sections with a mouse anti-IAPP antibody (α-IAPP, R10/99) that does not differentiate between monomeric and aggregated IAPP species (Supplementary Fig. 17). Islet amyloid fibrils were stained with thioflavin-S (ThioS) and anti-mouse secondary antibody was used as control (2^ndary Ab). Scale bars: 300 and 100 µm, respectively. b Representative images of T2D and control human pancreatic islets stained with mouse chimeric α-IAPP-O (^chα-IAPP-O, 30 nM; in blue, left panel), ThioS for extracellular amyloid deposits (in green, middle panel) and α-IAPP (E-5) for physiological human IAPP (in blue, right panel). Beta cells were visualized using anti-insulin antibody (in red) and merged images are shown. Scale bar: 100 µm. Similar results for (a) and (b) have been obtained in at least three independent experiments on pancreatic tissue sections from different T2D and control subjects. c Aggregation propensity of human IAPP (hIAPP) and biotinylated human IAPP (biotin-hIAPP) in solution measured by thioflavin-T (ThioT) fluorescence. Data are means ± s.e.m. from four replicates. d Binding kinetic analysis of α-IAPP-O to hIAPP (left panel) and biotin-hIAPP (right panel) using biolayer interferometry (BLI). e BLI analysis of α-IAPP-O Fab binding to hIAPP. BLI dose-response association and dissociation curves (black line), fitting curves (red line) and K_D constants (means ± s.e.m.) are derived from three independent runs (detailed in Supplementary Table 1). Association and dissociation are separated by a dashed line. Similar results for (c–e) have been obtained in three independent experiments.