Fig. 2. Localization of APPL relative to neuronal processes labeled with MAb 22C10. A, Larval CNS stained with anti-APPL (green) and 22C10 (red) antibodies. Boxed area including eye disk and brain lobe is shown at a higher magnification in B. B, In the eye stalk, APPL immunoreactivity colocalizes with 22C10 epitope, as revealed by the yellow color (open arrow). In the central neuropil of the brain lobe, APPL seems to be surrounding neuronal processes (white arrow). C, Optical section of a larval CNS stained with anti-APPL (green) and 22C10 (red) antibodies. Two boxed areas, comprising the optic lobe (D) in the brain lobe and the second thoracic neuromere (E) in the ventral ganglion, are shown at higher magnification in D and E, respectively.D, A section through the larval optic lobe stained with anti-APPL antibody (a), MAb 22C10 (b), and both antibodies (c). The central semicircular region stained with APPL corresponds to the neuropil of the medulla. Photoreceptor axons are intensely stained with both antibodies (small arrow). The thin arrow points to thick neuronal processes weakly stained with both antibodies. Thin fibers that run over the surface of the optic lobe are 22C10-immunoreactive and show APPL immunoreactivity concentrated in varicosities (arrowhead). E, A section through the second thoracic neuromere labeled with anti-APPL (a), 22C10 (b), and both (c). Notice that APPL immunoreactivity in this neuropil is not associated with 22C10-immunoreactive processes (arrow). In A–E, anterior is to the left. Scale bars: A, C, 50 μm; B, D, E, 25 μm.