Experimental autoimmune uveitis (EAU) is a disease model induced in genetically susceptible animals by injection of various soluble retinal antigens in adjuvant. The best characterized of these antigens is S-Ag. The uveitis it induces is critically dependent on the presence of activated T cells. It has been established that T cells become activated as a result of their interaction with primed antigen-presenting cells, a process through which the enciting protein is internalized and partially digested. Fragments from the original protein are then reexpressed on the cell surface where they can interact with T cells. Work is being carried out to identify and characterize those fragments which are responsible for the clinical response in animals as well as in humans.