Localization of T lymphocytes and macrophages in fibrous and complicated human atherosclerotic plaques.

The cellular composition of aortic atherosclerotic plaques was analyzed by immunocytochemistry using cell type-specific monoclonal antibodies. T lymphocytes and monocytes/macrophages were detected both in early, fibrous plaques, and in more advanced, complicated ones. Many smooth muscle cells in these plaques expressed the class II MHC antigen, HLA-DR. Since this antigen is inducible by T cell products, our findings suggest that T cell-smooth muscle interactions occur during atherogenesis.