PHENOTYPIC-EXPRESSION OF SURFACE-ANTIGENS OF RABBIT AORTIC SMOOTH-MUSCLE CELLS IN CULTURE - MONOCLONAL-ANTIBODY, 2P1A2, CHARACTERISTIC OF SMOOTH-MUSCLE CELLS PRESENT IN ATHEROSCLEROTIC PLAQUE, IS NOT CORRELATED WITH CELL-PROLIFERATION

The expression of smooth muscle cell (SMC) antigens was studied in culture by immunofluorescence and immunoelectron microscopy. As specific SMC markers, we used 2 monoclonal antibodies (MAb), 1PC1 and 2PIA2 which are able to detect atherosclerotic plaques in the rabbit. MAb 1PC1 recognizes an antigen expressed on the cell surface, starting on the 7th day in primary culture after serum activation, and then secreted. On a confluent SMC monolayers this antigen appears outside the cell as an important filamentous network. The kinetics of secretion of this external protein recognized by 1PC1 corresponds to the kinetics of the secretory phenotype described by Chamley-Campbell and Campbell (Atherosclerosis, 40 (1981) 347). 2PIA2 MAb is specific for SMCs exclusively present in the rabbit atherosclerotic plaque. We studied the degree of reactivity of 2PIA2 with SMCs during primary cell culture. This "atherosclerotic" antigen of SMCs recognized by 2PIA2 is expressed in culture conditions by SMCs from rabbit normal media. This antigen appears after 3 days of serum activation, and heparin growth inhibition does not interfere with its expression. 2PIA2 recognized antigen is expressed during all cell cycle phases without amplification. 3 days after fetal calf serum (FCS) stimulation of cells which are in G0 G1 89% are labelled by 2P1A2, 4 days later G0 G1 positive cells constitute 49%. We conclude that 2P1A2 immunolabelling on the SMC surface reflects an activated state which is not correlated with SMC proliferation. © 1990.