Abstract Autoimmune uveitis, a common cause of blindness, has an unknown etiology and no known cure. We have been studying experimental autoimmune uveitis (EAU) induced in mice deficient in various complement components, inhibitors, or receptors following active immunization with a retinal antigen and the adoptive transfer of already primed retinal antigen-specific T cells. Our findings strongly suggest that complement, particularly the complement receptors C3aR and C5aR, are required for not only the priming of autoreactive T cells in the periphery, but also the migration and/or re-stimulation of already activated pathogenic T cells in the retina. These findings suggest that these complement receptors could be new therapeutic targets for treating EAU and, eventually, autoimmune uveitis. In this proposed work, we will focus on the previously unknown role of complement in regulating the migration and/or re-stimulation of already primed autoreactive T cells in a target tissue, using EAU as a model. We will also elucidate the underlying mechanisms using various systemic and cell-specific complement-related gene knockout mice and other novel reagents. In addition, we will examine the efficacies and investigate the underlying mechanisms of our novel complement-targeted reagents for suppressing the migration and re- stimulation of previously activated uveitogenic T cells in the retina for the treatment of EAU both in mice and in rats. These studies will significantly improve our understanding of the pathogenesis of autoimmune uveitis and facilitate the development of novel complement-targeted therapeutics for the treatment of this blinding disease.