CHARACTERIZATION OF MEC-14.7, A NEW MONOCLONAL-ANTIBODY RECOGNIZING MOUSE CD34 - A USEFUL REAGENT FOR IDENTIFYING AND CHARACTERIZING BLOOD-VESSELS AND HEMATOPOIETIC PRECURSORS

Endothelial cell-specific molecules are potential targets For new ther apeutic strategies in the control of inflammatory reactions, immune re sponses and neoangiogenesis, We describe the production and characteri zation of MEC 14.7, a monoclonal antibody directed to murine endotheli al cells recognizing a glycosylated protein with an apparent molecular mass of about 100 kDa in cultured endothelioma cell lysate and about 80 kDa in lung lysate. MEC 14.7 antigen was selectively expressed by t he endothelium in vivo, particularly in small vessels and neoformed ca pillaries and by developing vascular structures in embryonal bodies, D eglycosylation of the molecule with neuraminidase, O- and N-glycanase showed that the MEC 14.7 epitope is neuraminidase-sensitive. MEC 14.7 antigen H-as purified from lung IS sates by chromatographic techniques , and sequenced internal peptides indicated:it was identical with muri ne CD34. Thus the apparent molecular mass of CD34 is heterogeneous, de pending on the glycosylation state in the different cell types. Immuno magnetic isolation and culture of MEC 14.7-positive bone marrow cells showed that this antibody recognizes hematopoietic progenitors (partic ularly myelomonocytic) and can be used in murine models of bone marrow reconstitution.