The uptake of horseradish peroxidase by the conjunctival epithelium of the guinea-pig.

It has been suggested that in immediate hypersensitivity of the guinea-pig conjunctiva, induced by the topical application of an antigen, the antigen is selectively taken up by the conjunctiva-associated lymphoid tissue. We tested this hypothesis by applying horseradish peroxidase (HRP) to the guinea-pig conjunctiva and studying its uptake by light- and electron microscopy. As early as 30 min after the application of the HRP, precipitate indicating the presence of HRP could be seen in the epithelial cells in membrane limited granules in the non-lymphoid and lymphoid epithelium. There was no selective uptake of HRP by the lymphoid-associated epithelial cells. We hypothesize that the epithelial cells of the conjunctiva, in contrast to those of the small intestine, phagocytose antigen and transfer it directly to the substantia propria of the conjunctiva for local immunologic processing.