A vascular endothelial cell antigen with restricted distribution in human foetal, adult and malignant tissues.

Human vascular endothelial cells were isolated by collagenase digestion of umbilical veins. Hybridomas secreting monoclonal antibodies were raised by fusing a mouse myeloma cell line to spleen cells from mice immunized with the isolated endothelial cells. A clone was selected which produced an antibody binding strongly to human umbilical vein endothelial cells. This antibody, EN 3, was shown to be directed against a major antigen on the surface of the cells, and appeared to be distinct from other antigens previously described on vascular tissues. The antibody bound to a lesser extent to umbilical artery endothelial cells and syncytiotrophoblast. Capillary endothelial cells in adult oesophageal tissues and tonsil were also labelled by the antibody, as were capillaries in a seminoma and infiltrating duct carcinoma of the breast. This well defined distribution in some foetal, adult and malignant tissues suggests that there is structural heterogeneity amongst endothelial cells in different sites, which may be linked to differences in differentiation or function.