Immune responses to retinal autoantigens and peptides in equine recurrent uveitis

PURPOSE. TO test the hypothesis that autoimmune mechanisms are involved in horses in which equine recurrent uveitis (ERU) develops spontaneously. METHODS. Material obtained from horses treated for spontaneous disease by t herapeutic routine vitrectomy was analyzed for total IgG content and Ige sp ecific fur S-Antigen (S-Ag) and interphotoreceptor retinoid-binding protein (IRBP). Thr cellular infiltrate of the vitreous was analyzed by differenti al counts of cytospin preparations and flow cytometry using equine lymphocy te-specific antibodies. Antigen-specific proliferation assays were performe d comparing peripheral blood lymphocytes (PBLs) with vitreal lymphocytes by stimulation with S-Ag and several S-Ag- and IRBP-derived peptides. RESULTS. The total IgG content of specimens from horses with ERU was very h igh with great variability among the investigated samples (11.5 +/- 8.0 mg) . Autoantibodies to S-Ag or IRBP or both were found in 72% of vitreous spec imens from horses with uveitis. The leukocytes infiltrates (up to 2 x 10(8) cells per sample) were dominated by lymphocytes (>90%) in most cases (22/3 2). Flow cytometry showed that more than 50% of these cells were CD4(+) T c ells. in vitro stimulation of vitreal lymphocytes, but not of PBL, showed a strong proliferative response to peptides derived from S-Ag or IRBP in 9 o f 12 patients. CONCLUSIONS. in the eyes of horses with ERU, IgG antibodies and autoreactiv e T cells specific for retinal antigens were detected. These results strong ly support the hypothesis that ERU is an autoimmune-mediated disease and is highly similar to recurrent uveitis in humans in both clinical and immunol ogic parameters.