Figure 3. The 2M6 antigen is an intracellular protein expressed by Müller glial cells of the chick retina. Hatchling chick retina was fixed, embedded in paraffin, sectioned, and stained with antibodies specific for 2M6 (A, red) and 5A11/Basigin (B, green), and neurofilaments (C, blue). The overlay image (D) includes 4',6-diamidino-2-phenylindole (DAPI) staining of DNA (amber). Note that 2M6, which is expressed by Müller cells, is most heavily distributed between the ganglion cell layer and the outer limiting membrane. In contrast, 5A11/Basigin, also expressed by Müller cells, extends beyond the ganglion cells into the nerve fiber layer to the Müller cell endfeet. In panels E through H, higher magnification images compare and contrast the intracellular Müller cell membrane staining of 2M6 (red) with the Müller cell plasma membrane staining of 5A11/Basigin (green). In panel E, the Müller cell perikarial region of the inner plexiform layer is shown. In panel F, the Müller cell bodies are shown. Müller cell processes at the outer plexiform/photoreceptor cell layer are shown in panel G, whereas Müller cell processes at the ganglion cell/nerve fiber layer are shown in panel H. Abbreviations are as follows: PC represents the photoreceptor cell layer; OPL represents the outer plexiform layer; INL represents the inner nuclear layer; IPL represents the inner plexiform layer; GC/NF represents the ganglion cell/nerve fiber layer. The magnification bars for A–D are 23.6 μm; the magnification bar for E is 9.3 μm; the magnification bars for F–H are 3.4 μm.