Preferential expression of a 130,000-Da cell surface protein by vascular wall cells in vitro and in vivo

Monoclonal antibodies have been raised against cell surface proteins of cultured bovine retinal pericytes. One antibody was selected, designated PC4, which preferentially stained primary cultures of bovine pericytes and smooth muscle cells, but not endothelial cells and fibroblasts. In freshly plated cells a homogeneous cell surface staining was observed, whereas in well-spread cells the antigen was concentrated at cell attachment sites. The antigen remained at these sites after spontaneous detachment of the cells. PC4 monoclonal antibodies reacted with a major protein of 130,000 Da and two minor antigens of 75,000 and 70,000 Da in immunoblots of extracts from cultured pericytes and smooth muscle cells and from fibroblasts cultured for an extended period of time. In frozen sections of bovine tissues the antigen was found in the vascular wall. There was no staining of skeletal muscle cells or duodenal smooth muscle cells, indicating that the antigen may be a specific component of the vascular wall.