RODS AND CONES CONTAIN ANTIGENICALLY DISTINCTIVE S-ANTIGENS

Purpose. S-antigen (48 kDa protein or arrestin) is known to be present in rod photoreceptors. Its localization in cones is less clear with s everal conflicting reports among various species examined. Methods. Th is study employed three different anti-S-antigen antibodies (a48K, a p olyclonal antiserum and two monoclonal antibodies, MAb A9-C6 and MAb 5 c6.47) and examined their localization in rods and cones of human and cat retinas. To identify the respective cone types, an enzyme histoche mical technique for carbonic anhydrase (CA) was employed to distinguis h blue cones (CA-negative) from red or green cones (CA-positive). S-an tigen localization was then examined by immunocytochemical staining of adjacent sections. Results. In human retinas, a similar labeling patt ern was seen with both a48K and MAb A9-C6, i.e., the rods and blue-sen sitive cones were strongly positive, whereas the red- or green-sensiti ve cones showed little immunoreactivity. All human photoreceptors show ed reactivity to MAb 5c6.47. In the cat retina, only CA-positive cones could be found. As in the human retina, both rods and cones of the ca t were positive for MAb 5c6.47. A difference from the labeling pattern in human retina was noted for the other S-antigen antibodies; a48K la beled rods and all of the cones, whereas MAb A9-C6 reacted strongly wi th the rods but showed no cone staining. Conclusions. These results su ggest that both rods and cones contain S-antigen but that they are ant igenically distinctive.