Detection of macrophages in atherosclerotic lesions with cytochrome oxidase.

The anaerobic metabolism of the arterial wall allows macrophages to be demonstrated therein by the cytochrome oxidase histochemical method. Monocytes (macrophages) in human fatty streaks (WHO grade I) or fibrofatty (WHO grade II) human atherosclerotic lesions are normally confined to subendothelial regions. Lesions complicated by ulceration, mural thrombosis or intimal haemorrhage (WHO grade III) showed numerous monocytes (macrophages) around newly-formed capillaries in focal areas of organization. By contrast with grades I and II atherosclerotic lesions, macrophages in lipid granulomas induced by subcutaneous injection of cholesterol oleate are more numerous and distributed throughout the lesion. The slow or absent resorption of lipid from atheromatous lesions may in part result from the paucity of macrophages therein.