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  • Title: Uveitogenic epitopes of retinal S-antigen are generated in vivo via an alternative antigen-presentation pathway.
    Author: Liversidge J, Dawson R, Dick AD, Forrester JV.
    Journal: Immunology; 1998 Jun; 94(2):271-8. PubMed ID: 9741352.
    Abstract:
    We have found that different antigen-processing pathways are involved in the induction of experimental autoimmune uveoretinitis (EAU) by the retinal autoantigens S-antigen and interphotoreceptor retinoid-binding protein (IRBP). Although in vitro T-cell proliferative responses to IRBP were completely inhibited in the presence of irreversible cysteine protease inhibitors, no significant reduction of S-antigen proliferative responses was found. Furthermore, acidic proteolysis of S-antigen by the cysteine protease cathepsin B prior to immunization radically reduced pathogenicity (disease severity). In addition, in vitro processing of S-antigen, but not IRBP, was also found to be resistant to the action of cycloheximide and lysosomotropic agents, inhibition of proliferation only occurring after extended exposure of antigen-presenting cells to methyl amine or high concentrations of chloroquine. These data indicate that an alternative pathway of antigen processing exists for S-antigen, which is independent of processing within the normal endolysosomal pathway and that uveitogenic peptides of naturally processed S-antigen bind to major histocompatibility complex class II antigens either at the cell surface or within very early endosomes where cathepsin B is inactive.
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