Breakdown of the blood-retinal barrier in S-antigen-induced uveoretinitis in rats

Experimental autoimmune uveoretinitis was induced in Lewis rats by footpad injection of purified, bovine retinal soluble antigen (S-antigen) with complete Freund's adjuvant. Control animals received adjuvant only. At the peak of ocular inflammation the animals received an intravenous injection of the tracer horseradish peroxidase, and the eyes were removed and processed for peroxidase cytochemistry. A breakdown of the blood-retinal barrier occurred at the level of the retinal venules. Peroxidase reaction product was demonstrable in the interendothelial tight junctions and in the perivascular spaces. Heavy infiltration of inflammatory cells was also found in and around the venular wall. The endothelial cells of venules and capillaries were hypertrophied and showed swollen endoplasmic reticulum and Golgi apparatus as well as increased numbers of ribosomes and cytoplasmic fibrils; pericytes and smooth-muscle cells showed a similar synthetic phenotype and the basal lamina of these cells was thickened.