Identification of the S-Endo 1 Endothelial-Associated Antigen

We have recently described a monoclonal antibody, S-Endo 1, recognizing a molecule constitutively expressed in all types of human endothelial cells. We showed that this protein around 118 kDa and located at the endothelial cell–cell junction presented sequence identity with MUC18 described as a tumor marker in human melanoma. The difference in antibodies immunoreactivity and antigen molecular weight heterogeneity observed between various cell types strongly suggested S-Endo 1 antigen isoforms expression.