Paraffin sections (4 \u03bcm thickness) of formalin-fixed human pancreases were treated with heat\/citrate buffer for antigen retrieval. Hpse was detected immunohistochemically using HP130 mouse anti-human Hpse mAb (Insight), with biotinylated anti-mouse IgG (1\/250) (PK-2200, Vector Labs) and avidin-biotin-complex (ABC reagent; PK-2200, Vector Labs). Background staining was checked using the corresponding isotype control Ig instead of the primary antibody. 3-amino-9-ethylcarbazole (AEC) was used as the chromogen. Stained sections were imaged using a light microscope with attached camera (Olympus BX41).