IMMUNOHISTOCHEMICAL DETECTION OF MACROPHAGE-DERIVED FOAM CELLS AND MACROPHAGE-COLONY-STIMULATING FACTOR IN PULMONARY ATHEROGENESIS OF CHOLESTEROL-FED RABBITS

In order to investigate the role of monocyte/macrophages and their rel ationship to the expression of macrophage colony-stimulating factor (M CSF) in pulmonary atherosclerosis, lungs were excised from rabbits tha t had been fed for 60 and 90 days on a diet containing 0.5% cholestero l. In the lungs, fatty streaks and elevated foam cell lesions predomin ated in the large or medium-sized elastic pulmonary arteries, while ma ssive accumulation of foam cells in the intima of muscular arteries pr oduced marked luminal narrowing and nearly complete occlusion. in thes e lesions, most of the foam cells were reactive with RbM2, a monoclona l antibody (mAb) against rabbit macrophages, while smooth muscle cell- derived foam cells were detected by mAb against smooth muscle actin in the deeper area of elevated foam cell lesions of elastic arteries. Ul trastructural observation confirmed the presence of monocytes in the i ntima, their differentiation into macrophages, and their transformatio n into foam cells in the atherosclerotic lesions. Immunohistochemical expression of MCSF was demonstrated in the endothelial cells, smooth m uscle cells and foam cells. A minor macrophage-derived foam cell popul ation was demonstrated to possess a proliferative capacity. These data suggest that MCSF is involved in the differentiation of monocytes int o macrophages, their transformation into foam cells, and their prolife ration during pulmonary atherogenesis.