Local activation of dendritic cells alters the pathogenesis of autoimmune disease in the retina.

Interest in the identities, properties, functions, and origins of local APC in CNS tissues is growing. We recently reported that dendritic cells (DC) distinct from microglia were present in quiescent retina and rapidly responded to injured neurons. In this study, the disease-promoting and regulatory contributions of these APC in experimental autoimmune uveoretinitis (EAU) were examined. Local delivery of purified, exogenous DC or monocytes from bone marrow substantially increased the incidence and severity of EAU induced by adoptive transfer of activated, autoreactive CD4 or CD8 T cells that was limited to the manipulated eye. In vitro assays of APC activity of DC from quiescent retina showed that they promoted generation of Foxp3(+) T cells and inhibited activation of naive T cells by splenic DC and Ag. Conversely, in vitro assays of DC purified from injured retina demonstrated an enhanced ability to activate T cells and reduced induction of Foxp3(+) T cells. These findings were supported by the observation that in situ activation of DC before adoptive transfer of β-galactosidase-specific T cells dramatically increased severity and incidence of EAU. Recruitment of T cells into retina by local delivery of Ag in vivo showed that quiescent retina promoted development of parenchymal Foxp3(+) T cells, but assays of preinjured retina did not. Together, these results demonstrated that local conditions in the retina determined APC function and affected the pathogenesis of EAU by both CD4 and CD8 T cells.