Antibodies to mouse lung capillary endothelium.

We are interested in developing monoclonal antibodies (MoAbs) that recognize specific cell types in the lung of BALB/c mice. Normal mouse lung homogenate was used to immunize F344 rats and hybridomas were produced by fusion of rat spleen cells with mouse myeloma SP 2/0. Two hybridomas were selected which produced MoAbs active in immunohistochemistry of lung cells. MoAb 273-34A and 411-201B both show extensive peroxidase staining of capillary endothelial cells within alveolar walls of lungs at the light microscopic level. To demonstrate cell specificity, immunoelectron microscopy with gold-labeled antibody was performed. Lightly fixed lungs were frozen and thin-sectioned before staining with MoAb and 5-nm gold particles coupled to secondary antibody. Quantitative analyses of these cryosections show that both antibodies, used at optimal concentrations, are specific for binding to capillary endothelial cells. More than 95% of the gold particles are associated with capillary endothelial cells on the thin side of the alveolar wall. When capillaries adjoined thick septa containing interstitial cells, about two thirds of the gold particles were associated with endothelial cells and about one quarter with interstitial cells. These MoAbs should be useful in studying the role of endothelial cells in toxic lung injury.