Tissue repair in the iris in experimental autoimmune uveoretinitis

Our previous work on rats with S-antigen-induced experimental autoimmune uveoretinitis showed iris tissue changes involving infiltration of inflammatory cells, destruction of the iris architecture, and breakdown of the blood-retinal barrier. The present study reports the remarkable ability of the iris to regenerate during the postinflammatory period. The iris regenerates 50% of its architecture by Day 20 postimmunization. The number of lymphocytes and polymorphonuclear leukocyte (PMNs) was relatively high at this stage. Many capillaries showed abnormal endothelial cells. Unmyelinated nerve axons were often seen near blood vessels. The iris stroma was edematous. By Day 30, approximately 95% of the iris had regenerated, the number of lymphocytes and PMNs decreased, and the number of macrophages increased. Most capillaries looked normal and numerous axons in different stages of myelination were apparent. The stroma, the dilator muscle, and the posterior epithelium were almost completely restored. By Day 45, the iris appeared to be virtually normal. Most striking was the abundance of myelinated nerve axons located near blood vessels. Type I collagen immunoreactivity in vascular endothelial cells increased from Day 20 to Day 60 postimmunization, suggesting that blood vessel endothelial cells may play a role in collagenization of the iris stroma.