CD133 expression in endodermal, mesodermal and neuroectodermal tissues. Endodermal: A) stomach, B) duodenum, C) gall bladder, D) liver, E) pancreas, F) salivary gland. Mesodermal: G) kidney, H) endometrium in secretory state, I) lymphatic tissue (tonsil) with a germinal center. Neuroectodermal: J) brain (cortex cerebri), K) skin, L) mammary gland. Retina staining (neuroectodermal) is shown in Figure 1A and colon staining (endodermal) in Figure 3A. Note the apical/endoluminal membrane staining in glandular epithelia in general. In the stomach (A), duodenum (B) and colon (3A), CD133 expression is restricted to cells at the basal part of the mucous membrane. In the gall bladder (C), biliary ducts of the liver (D), endometrium (H) and mammary gland (L), there is homogenous apical membrane staining. In the pancreas (E) and the salivary gland (F), homogenous endoluminal staining of the smallest ductal structures is present. In the kidney (G), all cells of the Bowman's capsule seem to express CD133 in the cytoplasm and membrane, whereas apical membrane staining is present in some of the duct cells (asterisk). No staining was detected in tonsils (I), lymph nodes (not shown), cortex cerebri (J) or skin (K). Weak color in the cytoplasm of basal cells in the skin is supranuclear melanin pigment. A-C, I-L = ×200, scale bar in A = 100 μm. D-H = ×400, scale bar in A = 50 μm.