In view of the increasing awareness of corneal abnormalities in diabetes, five diabetic and five nondiabetic postmortem corneas were investigated. Indirect fluorescent antibody techniques were used for the detection of immunoglobulin, complement components, fibrinogen, and fibronectin, as some of these had already been found in the kidney, pancreas, and skin of diabetic patients. There was no obvious difference in the deposition of IgG, IgA, IgM, fibrinogen, or fibronectin between diabetic and control corneal specimens. Five diabetic specimens versus three control specimens demonstrated positive staining at 1:50 dilution for complement components Clq, C3, and C4. This staining was primarily present in the epithelium. Of greater interest was the finding that complement components were present in the basement membrane of two diabetic patients, but were not found in nondiabetic patients. In conclusion, diabetic corneas demonstrate unusual staining for complement components in the epithelial basement membrane.
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