The epithelial origin of the isolated BOECs was
confirmed by subjecting the cells to immunocytochemical
staining for the expression of cytokeratins using monoclonal
mouse antihuman cytokeratin antibodies (clone AE1/
AE3), biotinylated goat antimouse antibodies, streptavidin–
horseradish peroxidase, and AEC substrate-chromogen
(Dako, Denmark) according to the manufacturer’s instructions.