A monoclonal antibody marker for the paraboloid region of cone photoreceptors in turtle retina.

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/biotin-peroxidase 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 paraboloid.