Acute anterior uveitis (AAU) is the most common form of intraocular inflammation of unknown etiology and is a major cause of visual disability in our society. The recurrent nature of the disease can lead to permanent visual loss from the secondary complications of cystoid macular edema, posterior subcapsular cataract or glaucoma. Experimental autoimmune anterior uveitis (EAAU)is an organ specific autoimmune disease of the eye, which resembles AAU. It is produced in the Lewis rat by an antigen specific CD4+ T cell response to melanin-associated antigen (MAA) derived from bovine iris and ciliary body. We have recently purified the pathogenic antigen to homogeneity and our results suggest that it is a 22 kD fragment of Type I collagen, alpha-2 chain. The pathogenic antigen is tissue specific, being localized solely to the eye. The specific aims of our proposal are: A. Determine the primary structure of MAA; B. Identify the immunogenic and pathogenic epitopes of MAA; C. Modify the course of EAAU. The opportunity to study a clinically relevant animal model of AAU may allow the identification of treatment modalities which may prevent the occurrence of AAU rather than solely allow treatment of the acute episode, which is the current state of the art.