Immunologic and biochemical properties of several retinal proteins bound by antibodies in sera from animals with experimental autoimmune uveitis and uveitis patients

Abstract

Sera from guinea pigs and rabbits with and without experimental autoimmune uveitis (EAU) induced by immunization with retina, choroid, optic nerve, retinal rod outer segments (ROS) and purified bovine S-antigen were tested for the ability to immunoprecipitate 125I-labeled, detergent-solubilized bovine retinal proteins. The results demonstrate that three major protein antigens with m.w. of 50,000 (p50), 35,000 (p35) and 27,000 (p27) and several minor activities between 30,000 and 60,000 m.w. are recognized by antibodies from these animals. The p50 component was immunoprecipitated by sera from animals immunized with whole retina homogenate, the high speed supernatant of whole retina homogenate, ROS, and S-antigen, and has been identified as S-antigen in competition experiments. The p35 band appeared when sera were used that were raised against antigen preparations containing membrane-bound retinal protein, i.e., whole retina homogenate, ROS, and washed ROS, and thus appears to be an ROS membrane protein. The p27 band was found when sera raised against ROS, washed ROS, optic nerve and whole retina homogenate were used, suggesting it is a membrane-bound antigen common to ROS and optic nerve. Serum from animals immunized with homologous choroid did not immunoprecipitate a detectable product. S-antigen and p35 were also precipitated by some uveitis patient sera. Because S-antigen is also an ROS protein as is rhodopsin, a putative uveitogenic retinal antigen, ROS appear to be an unusually rich source of autoantigenic proteins. S-antigen was also shown to be synthesized in the retina, and the primary translation product was indistinguishable from purified S-antigen by SDS-PAGE, thus eliminating the possibility that it is derived from or is cross-reactive with the 67,000 m.w. rhodopsin kinase.