A 90-kd surface antigen from a subpopulation of smooth muscle cells from human atherosclerotic lesions.

A monoclonal antibody, designated 10F3, that reacts with an antigen with a molecular weight of 90,000 daltons has been obtained after immunization of BALB/c mice with long-term cultured smooth muscle cells (SMC) originally isolated from fetal human aorta (fSMC). In adults the antigen is present on venous, arterial and capillary endothelial cells of heart, kidney, liver, spleen, intestine, skin, uterus, placenta, and arteries only, as shown by immunohistochemical investigation using the PAP technique. The antigen 10F3 is also present on the mesenchymal cells of human fetal tissues (7 and 18-week-old fetuses) and on SMC of 7-week-old fetal aorta, and a subpopulation of cells reacting with 10F3 antibody also has been found in atherosclerotic intima. Double staining using 10F3 antibody and muscle actin-specific monoclonal antibody HHF-35 showed that the antigen-positive cells are smooth muscle cells. In primary culture of adult SMC, antigen-positive cells were detected 2 days after seeding (about 90% positive in medial and intimal cultures). It is suggested that 10F3 is a mesenchymal antigen that, lost during differentiation by cells other than endothelium, but expressed again by the SMC involved in atherogenesis.