Treatment of experimental autoimmune uveitis in the rat with systemic succinylacetone

The effects of succinylacetone (SA) on the development of S-antigen-induced experimental autoimmune uveitis (EAU) in the rat were studied. SA totally suppressed EAU at Day 14 when animals were treated with a constant infusion of 1.80 mg/hr by an osmotic minipump. Three intervals of treatment with this dose rate were used (Day 0-7, Day 7-14, or Day 0-14) and, regardless of dosage interval, suppression of the disease was complete. There was a significant inhibition of S-antigen-induced lymphocyte proliferative responses in cells from popliteal lymph nodes (P less than 0.009) as well as a significant decrease of S-antigen antibody production. Animals treated with SA at a rate of 0.90 or 0.45 mg/hr developed EAU in a dose-related fashion. Animals treated with 1.8 mg/hr from Day 7-14 but killed at Day 30 had 100% breakthrough of the disease. Succinylacetone inhibits the expression of EAU and significantly suppresses the immune response to S-antigen. However, once therapy is discontinued the high incidence of breakthrough suggests a reversible noncytotoxic mechanism of immune modulation.