THE ROLE OF EOSINOPHILS AND NEUTROPHILS IN HELMINTH-INDUCED KERATITIS

PURPOSE. Intrastromal injection of mice with antigens from the parasit ic helminth that causes river blindness (Onchocerca volvulus) induces eosinophil recruitment to the corneal stroma at the time of maximum co rneal opacification and neovascularization. The present study was cond ucted to examine the role of eosinophils and neutrophils in onchocerca l keratitis in control C57B1/6 mice and in interleukin-5 gene knockout (IL-5(-/-)) mice. METHODS. C57B1/6 and IL-5(-/-) mice were immunized subcutaneously and injected intrastromally with soluble O. volvulus an tigens. Mice were killed at various times thereafter. Development of k eratitis was assessed by slit lamp examination, and inflammatory cells in the cornea were identified by immunohistochemistry. RESULTS. A bip hasic recruitment of inflammatory cells was observed in C57B1/6 mice; neutrophils predominated during the first 72 hours after intrastromal injection and subsequently declined, whereas eosinophil recruitment in creased as time elapsed and comprised the majority (90%) of cells in t he cornea by day 7. In contrast, neutrophils were the predominant infl ammatory cells in IL-5(-/-) mice at early and late time points and wer e associated with extensive stromal damage and corneal opacification a nd neovascularization. Eosinophils were not detected in these mice at any time. CONCLUSIONS. In the absence of eosinophils, neutrophils can mediate keratitis induced by helminth antigens. Together with the earl y neutrophilic infiltrate in control animals, these observations indic ate that neutrophils have an important role in onchocercal keratitis.