CHARACTERIZATION OF EN4 MONOCLONAL-ANTIBODY - A REAGENT WITH CD31 SPECIFICITY

EN4 MoAb was originally described as a MoAb that reacts specifically w ith human endothelial cells, and the reagent was not assigned to any o f the presently known CD. Here, we provide evidence indicating that EN 4 reacts with the CD31 antigen. Thus, EN4 stains strongly murine fibro blasts transfected with the human CD31 gene. Furthermore, SDS-PAGE ana lysis of immunoprecipitates of cell lysates from surface-iodinated Jur kart T cells demonstrated that EN4 and reference CD31 MoAb recognized the same antigen, of 130 kD mol. wt. Finally, both EN4 and CD31 gave t he same pattern of reactivity when tested on tonsillar or peripheral b lood lymphoid cells by FACS analysis or by immunohistochemistry on sec tions of a variety of human tissues. EN4, however, proved consistently more efficient than the reference anti-CD31 MoAb as judged by both th e intensity of fluorescence or of tissue staining. This property has t hus allowed a better characterization of the tissue and cellular distr ibution of CD31.