Recurrent intraocular inflammation in endotoxin-induced uveitis.

PURPOSE: Endotoxin-induced uveitis (EIU) in rats and mice peaks 24 hours after endotoxin injection and is commonly assumed to be a monophasic disease. This study examined intraocular inflammation at later time points to determine whether endotoxin injection can induce recurrent intraocular inflammation in strains of mice with high or moderate levels of susceptibility to EIU. METHODS: EIU was elicited in two mouse strains with high (C3H/HeN) and moderate (FVB/N) susceptibility, by means of intraperitoneal injections of Salmonella typhimurium endotoxin. Inflammatory cells in the anterior and posterior segments of the eye were counted by a masked observer on histologic sections of eyes from 1 to 17 days after endotoxin injection. RESULTS: A bimodal distribution of inflammatory cell infiltration was noted in eyes from C3H/HeN mice. As previously reported, inflammation peaked at 24 hours after endotoxin injection. However, a second, more pronounced peak of intraocular inflammation occurred approximately 5 days after endotoxin injection. FVB/N mice had a single peak of intraocular inflammation 4 days after injection. CONCLUSIONS: Endotoxin injection in C3H/HeN elicits recurrent intraocular inflammation. The previously unrecognized second peak of inflammation is more severe than the initial inflammatory disease. Studies on this second inflammatory peak may be useful in determining the pathogenesis of recurrent uveitis in humans.