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Abstract
Cells bearing a smooth muscle cell marker--alpha-actin and a macrophage marker--CD68
antigen were immunocytochemically identified on 'en face' preparations of human aortic
intima. Cells, expressing smooth muscle alpha-actin, macrophage CD68 antigen and both
markers, i.e. smooth muscle cells possessing the macrophage antigen, were identified
both in grossly normal aortic areas and in atherosclerotic lesions (fatty streaks
and atherosclerotic plaques). CD68-positive smooth muscle cells were most common in
the lipid-rich areas: fatty streaks and atherosclerotic plaque shoulders. Cells expressing
smooth muscle alpha-actin and CD68 were also revealed in primary cultures prepared
from grossly normal and atherosclerotic intima. Cells expressing both antigens were
found in all examined cultures. The proportion of these cells in cultures from grossly
normal areas and atherosclerotic plaques was similar: 14.5 +/- 4.1 and 14.6 +/- 4.8%,
respectively. Cultures from fatty streaks had a higher content of cells expressing
both antigens: 25.1 +/- 7.0%. Modified low density lipoprotein-induced intracellular
lipid accumulation in cells cultured from grossly normal intima led to a three-fold
increase in the number of cells sharing alpha-actin and CD68 antigen. Accumulation
of latex beads by phagocytosis had a similar effect. It was suggested that in atherosclerotic
lesions intracellular lipid accumulation and other stimulators of phagocytosis may
provoke the expression of macrophage-associated antigen CD68 in settled cells of the
subendothelial intima of human aorta.