Basophils in vernal conjunctivitis in humans: an electron microscopic study.

The histopathological changes of vernal conjunctivitis comprise stromal infiltration by lymphocytes, plasma cells, and neutrophilic, eosinophilic, and basophilic leukocytes and epithelial invasion by mast cells and eosinophils. Blood vessels show swelling and death of endothelial cells and increased permeability with associated extravasation of erythrocytes and fibrin. The presence of basophils in ocular tissue has not been reported previously, and their occurrence in conjunction with the other pathological changes enables vernal conjunctivitis to be compared with, and classified as a manifestation of, delayed-type hypersensitivity of the cutaneous basophil type. Thus the mechanism is probably a mixture of both delayed and immediate immunological responses.