Recurrent intraocular inflammation in endotoxin-induced uveitis

PURPOSE. Endotoxin-induced uveitis (EIU) in rats and mice peaks 24 hours af ter endotoxin injection and is commonly assumed to be a monophasic disease. This study examined intraocular inflammation at later time points to deter mine whether endotoxin injection can induce recurrent intraocular inflammat ion in strains of mice with high or moderate levels of susceptibility to EI U. METHODS. EIU was elicited in two mouse strains with high (C3H/HeN) and mode rate (FVB/N) susceptibility, by means of intraperitoneal injections of Salm onella typhimurium endotoxin. Mammatory cells in the anterior and posterior segments of the eye were counted by a masked observer on histologic sectio ns 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 i njection. FVB/N mice had a single peak of intraocular inflammation 4 days a fter injection. CONCLUSIONS. Endotoxin injection in C3H/HeN elicits recurrent intraocular i nflammation. The previously unrecognized second peak of inflammation is mor e severe than the initial inflammatory disease. Studies on this second infl ammatory peak may be useful in determining the pathogenesis of recurrent uv eitis in humans.