An 18-mer peptide derived from the retinal S antigen induces uveitis and pinealitis in primates.
S-antigen, a photoreceptor cell protein, induces a predominantly T-cell mediated autoimmune uveitis in many vertebrate animals, including primates. Because of this activity and the finding of immune responses to S antigen in patients with uveitis, this protein has been implicated in the pathogenesis of uveitis in humans. Peptide M, an 18-amino acid component of S antigen, has previously been shown to be highly uveitopathogenic in rats and guinea pigs. We report here that peptide M is immunopathogenic in some monkeys, producing inflammatory changes in eyes and pineal glands similar to those induced by native S antigen. Monkeys with disease also developed intense immune responses to peptide M, measured by the lymphocyte proliferation assay. In addition, lymphocytes from these monkeys reacted against whole S antigen. Furthermore, lymphocytes from certain monkeys immunized with whole S antigen responded well against peptide M, thus indicating that this peptide is an immunodominant epitope in these animals. Two of the four monkeys immunized with peptide M did not develop disease. Lymphocytes from these two animals did not respond in culture against the peptide. Following immunization with the whole protein, these monkeys were capable, however, of developing cellular immunity against S antigen and one of them developed disease. The possible involvement of peptide M in the pathogenesis of uveitis in humans is discussed.