title: Rods and cones contain antigenically distinctive S-antigens.
abstract: OBJECTIVE
  S-antigen (48 kDa protein or arrestin) is known to be present in rod photoreceptors. Its localization in cones is less clear with several conflicting reports among various species examined.
  
  
  METHODS
  This study employed three different anti-S-antigen antibodies (a48K, a polyclonal antiserum and two monoclonal antibodies, MAb A9-C6 and MAb 5c6.47) and examined their localization in rods and cones of human and cat retinas. To identify the respective cone types, an enzyme histochemical technique for carbonic anhydrase (CA) was employed to distinguish blue cones (CA-negative) from red or green cones (CA-positive). S-antigen localization was then examined by immunocytochemical staining of adjacent sections.
  
  
  RESULTS
  In human retinas, a similar labeling pattern was seen with both a48K and MAb A9-C6, i.e., the rods and blue-sensitive cones were strongly positive, whereas the red- or green-sensitive cones showed little immunoreactivity. All human photoreceptors showed 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 cat were positive for MAb 5c6.47. A difference from the labeling pattern in human retina was noted for the other S-antigen antibodies; a48K labeled rods and all of the cones, whereas MAb A9-C6 reacted strongly with the rods but showed no cone staining.
  
  
  CONCLUSIONS
  These results suggest that both rods and cones contain S-antigen but that they are antigenically distinctive.
authors.affiliation: Department of Ophthalmology, West Virginia University Health Sciences Center, Morgantown.
authors.forename: T M
authors.initials: TM
authors.lastname: Nork
authors.forename: N J
authors.initials: NJ
authors.lastname: Mangini
authors.forename: L L
authors.initials: LL
authors.lastname: Millecchia
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000941:Antigens / Q000032:analysis*; D019393:Arrestin; D001324:Autoantigens / Q000032:analysis*; D002256:Carbonic Anhydrases; D002415:Cats; D005136:Eye Proteins / Q000032:analysis*; D006801:Humans; D007124:Immunoenzyme Techniques; D008969:Molecular Sequence Data; D010786:Photoreceptor Cells / Q000276:immunology*
chemical_list: D000941:Antigens; D019393:Arrestin; D001324:Autoantigens; D005136:Eye Proteins; D002256:Carbonic Anhydrases