Immune cells responding to ouabain-induced retinal degeneration identify as macrophages. A–F. Retinal cryosections from transgenic mpeg1:mCherry fish following intravitreal injection of saline (A–C) or ouabain (D–F) were immunolabeled with L-plastin (green) and counterstained with DAPI (blue). A–C. In saline-injected controls, all L-plastin+ immune cells (green) co-label with the macrophage marker mpeg1:mCherry (red); co-label is yellow (A–C), indicating ramified microglia. D–F. Following ouabain injection, ameboid, L-plastin+ immune cells accumulate (green, D–F), but only a subset of these also express the mpeg1:mCherry reporter (yellow, D–F). Arrowheads indicate vacuoles in selected cells. G–I High magnification images of retinal cryosections from ouabain damaged retinas stained with H&E reveal classical characteristics of phagocytic macrophages in accumulating immune cells (G–I and G’–I’), indicating that these accumulating immune cells are in fact macrophages. These features include irregular shapes of cell bodies and nuclei, cytoplasm similar in color to the environment, space immediately surrounding the cell borders, and the presence of vacuoles (asterisks). H’ Pyknotic nucleus within the cytoplasm of a macrophage (arrow), indicating phagocytosis of apoptotic cells. The red signal in the ONL in images A–F is due to autofluorescence from photoreceptors. Scale bar in A (applies to A–F) = 20 μm. Scale bar in G (applies to G–I and G’–I”) = 10 μm
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