Control of the specificity of CD133 staining. A) A section of retina showing strong membranous and cytoplasmic staining concentrated in the apical part of both cone and rod cells. Weak positivity is noted in a layer basal to the cone and rod nuclei. B) A parallel retina section processed similarly to A, except from the addition of primary antibody. The cell layers are rods and cones (1), horizontal, bipolar and amacrine cells (2) and ganglion cells (3). A, B = ×400, scale bar = 100 μm. C) Western blot stained with the two antibodies AC141 (lanes 1 and 2) and AC133 (lanes 3 and 4). Only AC133 recognized the expected band of around 117 kDa. T and N denote protein extracts from a pancreatic ductal adenocarcinoma and from normal pancreas, respectively. The band sizes (kDa) of the molecular weight standard in lane 5 are listed to the right.