A new perspective of S-antigen from immunochemical analysis

Elucidation of the amino acid sequences of retinal S-antigens from several species has allowed the fine dissection of T cell and antibody epitopes using synthetic peptides. S-antigen, isolated from retinal rod photoreceptor cells, elicits experimental autoimmune uveoretinitis (EAU), a predominantly CD4+ T-cell mediated autoimmune disease of the retina and uveal tract of the eye and pineal gland. Three uveitogenic T cell lines, R9, R17 and R208, prepared against native bovine S-antigen, human S-antigen and cyanogen bromide peptide CB123, respectively, were used to identify the T cell recognition sites responsible for uveitogenic and proliferative responses. T cell epitopes were found to be clustered into 6 regions, some of which were species-specific. The two synthetic peptides known to actively induce EAU, residues 286–297 and 303–314 of bovine S-antigen, were unable to induce significant proliferative responses in any of the three T cell lines. However, both of these sites were adjacent to synthetic pept...