TISSUE-REPAIR IN THE IRIS IN EXPERIMENTAL AUTOIMMUNE UVEORETINITIS

Our previous work on rats with S-antigen-induced experimental autoimmu ne uveoretinitis showed iris tissue changes involving infiltration of inflammatory cells, destruction of the iris architecture, and breakdow n of the blood-retinal barrier. The present study reports the remarkab le ability of the iris to regenerate during the postinflammatory perio d. The iris regenerates 50% of its architecture by Day 20 postimmuniza tion. The number of lymphocytes and polymorphonuclear leukocyte (PMNs) was relatively high at this stage. Many capillaries showed abnormal e ndothelial cells. Unmyelinated nerve axons were often seen near blood vessels. The iris stroma was edematous. By Day 30, approximately 95% o f the iris had regenerated, the number of lymphocytes and PMNs decreas ed, and the number of macrophages increased. Most capillaries looked n ormal and numerous axons in different stages of myelination were appal ent. The stroma, the dilator muscle, and the posterior epithelium wer e almost completely restored. By Day 45, the iris appeared to be virtu ally normal. Most striking was the abundance of myelinated nerve axons located near blood vessels. Type I collagen immunoreactivity in vascu lar endothelial cells increased from Day 20 to Day 60 postimmunization , suggesting that blood vessel endothelial cells may play a role in co llagenization of the iris stroma. (C) 1995 Academic Press, Inc.