CD133 expression in adult and fetal pancreas. A-F) Normal adult pancreas. Note the apical/endoluminal staining of the ducts and that the islets of Langerhans (asterisks in A) are negative. See also Figure 2E. B) Double staining with CD133 (brown) and cytokeratin 19 (red) showing abundant co-expression of the two markers. The insert is a higher magnification showing CD133-positive, CK19-negative cells in the region connecting ducts and acini (arrow). C) Double staining with CD133 (brown) and chromogranin A (red). No co-expression was detected. D) A duct with a single cell exhibiting cytoplasmic CD133 positivity (arrow). E) Acini with apical/endoluminal expression whenever a visible lumen is present. The arrow points to a cell in centroacinar position, apparently having cytoplasmic expression. F) A CD133-negative islet. G, H) Fetal pancreas at gestational week 18, low and high magnification. Staining as in C. I) Chronic inflammation and atrophic exocrine tissue. Staining as in C. Note the similarity to G in general architecture and the difference in distribution of chromogranin A-positive endocrine cells. A-C = ×400, scale bar in A = 50 μm. D-F, H = ×1000, scale bar in A = 20 μm. G, I = ×200, scale bar in A = 100 μm.