CORTICOSTEROIDS ENHANCE S-ANTIGEN EXPRESSION IN NONRETINAL OCULAR-TISSUES OF RATS WITH EXPERIMENTAL AUTOIMMUNE UVEITIS

S-antigen (S-Ag), a major protein on the retinal photoreceptor cell, c an induce experimental autoimmune uveitis (EAU). We have previously de tected S-Ag and its mRNA in irises of chronic uveitis patients receivi ng long-term steroid therapy. To further investigate the effect of ste roid therapy on ocular tissue, we compared levels of S-Ag and its mRNA in EAU rats with and without steroid treatment. EAU was induced in 72 Lewis rats by two footpad injections of S-Ag. The rats were then trea ted with Depo-Medrol or phosphate-buffered saline by intramuscular inj ection. Eyes were collected at different time points. S-Ag mRNA was de tected in the lens epithelium, trabecular meshwork, iris, and ciliary body of 47.2% of the steroid-treated group vs 22.2% of the controls. S -antigen was also detected in 30.6% of the eyes of the treated group v s 16.7% of the controls. S-Ag and its mRNA was found only in the retin a of normal rats. These results support the hypothesis that prolonged corticosteroid therapy in uveitic patients might enhance the expressio n of S-Ag in nonretinal ocular tissues and might contribute to the ocu lar side effects of corticosteroid.(C) 1994 Academic Press, Inc.