Immunohistochemical and ultrastructural demonstration of the lymphocyte-macrophage interaction in human aortic intima

Using immunohistologic methods coupled with electron microscopic analysis, human arterial intima such as normal areas on gross inspection, fatty streaks, and fibrous or atheromatous plaques was examined. Special emphasis was put on the possible direct interactions between the infiltrated cells of the aortic intima. In the lesions of fatty streaks and atheromatous plaques including the fibrous cap and the shoulder region, OKM1+ LeuM3+ macrophages as well as macrophage foam cells intimately coexisted with OKT3+ lymphocytes. It was worthy of note that such colocalization of macrophages and T-lymphocytes was detectable in some areas of grossly normal intima. In terms of T-cell subsets, suppressor/cytotoxic T-lymphocytes (OKT8+) outnumbered helper/inducer T-lymphocytes (OKT4+). Electron microscopic observations demonstrated the ultrastructural aspect of macrophage-T-lymphocyte interactions. The most striking finding was direct apposition of the lymphocytes to macrophages or macrophage foam cells, often forming rossette-like organizations closely resembling satellitosis. The direct cellular contact was noted not only between lymphocytes and macrophages but also among lymphocytes or macrophages themselves. These observations suggest that a specific in situ cell-mediated hypersensitivity plays an important role in the pathogenesis of human atherosclerosis.