Monoclonal antibodies that specifically label one or more cell types in retina have been produced; however, only a few antibodies that, in addition, recognize distinct subcellular structures in these cells have been reported. During a search for monoclonal antibodies that bind to specific cell types in the turtle (Pseudemys scripta elegans)retina, we obtained an antibody (20–93; an IgG) that labels the inner segment of cone photoreceptors. Ultrastructural immunocytochemistry using immunogold and avidin/biotinperoxidase techniques showed that 20–93 antigen is localized to the paraboloid, a region specifically involved in glycogen metabolism in cones. In addition, a few bipolar cells were found to be labeled. The monoclonal antibody showed limited species cross-reactivity and failed to stain mouse, rat, rabbit, dog, cow,Anolis, and human retinas. Immunoblotting showed that monoclonal antibody 20–93 binds to a 40 KDa protein that is present in the retinal membrane. The antibody should be useful in immunological studies of the cone parab
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