Antibodies specific to the plasma membrane of rat lung microvascular endothelium

The highly purified, luminal domain of rat lung endothelial plasma membranes was used as an immunogen to obtain monoclonal antibodies to the endothelial cell surface. The procedure was highly efficient, yielding antibodies which recognize three seemingly novel endothelial integral membrane glycoproteins of molecular weights of 170, 114, and 95 kDa, respectively. By immunofluorescence, two of these antigens (170 and 95 kDa) appeared to be uniquely expressed by the lung microvascular endothelium. The third one, the 114-kDa polypeptide, was detected in the continuous endothelium of the lung, but also in the fenestrated endothelia of pancreas, intestinal villi, and kidney peritubular capillaries. Partition in Triton X-100-soluble and -insoluble plasmalemmal components suggests that two of these novel endothelial antigens (170 and 114 kDa) are specific for the plasma membrane proper only, while that of 95 kDa is present both in the caveolae and on the rest of the cell surface.