ULTRASTRUCTURAL AND IMMUNOCYTOCHEMICAL STUDIES OF IRIS VESSELS IN RATS WITH EXPERIMENTAL AUTOIMMUNE UVEORETINITIS

In this study, we describe the ultrastructural and immunocytochemical changes that occur in the iris of rats with experimental autoimmune uv eoretinitis (EAU). General changes include perivascular infiltration o f inflammatory cells, followed by hemorrhage and extensive tissue dest ruction. Alterations in the iris epithelium were also noted. A breakdo wn in the blood-iris barrier was demonstrated in some vessels at the p eak of inflammation; peroxidase reaction product was seen in the basem ent membrane and perivascular spaces. We found that, in inflamed iris vessels, endothelial cells and smooth muscle cells become hypertrophic and show increased amounts of synthetic organelles. This finding is s imilar to our previous observations on endothelial cells and smooth mu scle cells in retinal vessels in EAU (1). In addition, as was reported in the retinal vascular basement membrane in EAU (2), there is an inc rease in immunoreactivity of several extracellular matrix molecules in the iris vascular basement membrane; during inflammation, there is a significant increase in immunoreactivity of collagen types I and III, entactin, fibronectin, and laminin. Activated endothelial cells and sm ooth muscle cells are likely to be involved in the synthesis of certai n of these matrix molecules.