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A model of topically induced ocular anaphylaxis was developed. Male Sprague-Dawley rats were immunized by intraperitoneal injections of egg albumin (EA) and alum and topically challenged with EA. Application of EA induced clinical (conjunctival edema) and histologic (mast cell degranulation) signs of anaphylaxis, when the antigen was preceded by topical application of dithiothreitol (DTT), a mucolytic agent. Rats challenged by four EA applications did not differ significantly in clinical edema or mast cell degranulation from those challenged by one EA application at the same (0.1 M DTT) pretreatment level, but there was significantly greater histologically assessed edema in the eyes challenged four times.

Cellular events in the rat conjunctiva were studied at 1, 6 and 24 h following the topical application of leukotriene B4. A significant increase was noted in the number of eosinophils (p less than 0.01) and neutrophils (p less than 0.05) at 1 h and only in eosinophils at 6 h after leukotriene B4 application at the 2-micrograms dose. At the 200-ng dose, the eosinophil count was significantly elevated at 1 h only, and the number of neutrophils was not significantly changed at any time point. No significant increase in cell counts was observed at the 20-ng dose. In conclusion, certain doses of topically applied leukotriene B4 significantly increased the number of eosinophils and neutrophils in the rat conjunctiva.