Cellular response to intravitreal injection of endotoxin and xanthine oxidase in rabbits

In the present study, the ocular inflammatory response to intravitreally injected endotoxin and xanthine oxidase was studied and the cellular response of the anterior and posterior segments was contrasted. There was a clear dose response relationship to both compounds in aqueous humor protein concentration and aqueous and vitreous humor white cell number. Xanthine oxidase and low doses of endotoxin (0.25 and 1.0 ng) produce a mainly mononuclear response in the anterior segment. Higher doses of endotoxin (10 and 100 ng) produced a predominantly neutrophilic response. Cellular infiltration into the posterior segment differed qualitatively and quantitatively from the anterior segment in response to the same stimuli. Myeloperoxidase (MPO) activity (a marker for neutrophils) of the iris-ciliary body was increased only in those eyes with a large neutrophilic response and thus is not recommended for use as a definitive index of the ocular inflammatory response, but may be a useful adjunct for such studies.