Structural heterogeneity and contacting interactions of vascular dendritic cells in early atherosclerotic lesions of the human aorta.

Structural heterogeneity and contact interactions of vascular dendritic cells (VDCs) in early atherosclerotic lesions of the human aortic intima were studied using electron microscopy. VDCs were identified through their ultrastructural features which were typical of dendritic cells. From their morphological characteristics, two phenotypes of VDCs (types I and II) were distinguished. VDCs were found to be distributed throughout atherosclerotic lesions, and through their processes were seen to be in contact with each other and with other intimal cells. VDCs developed multiple contacts with intimal macrophages, smooth muscle cells and foam cells. Smooth muscle cells contacting VDCs were mainly of synthetic phenotype suggesting the involvement of VDCs in the regulation of cell phenotypes. Occasionally, contacts between VDCs and lymphocyte-like cells were also observed. We speculate that through cell-to-cell contacts, VDCs are involved in immune reactions in atherosclerotic lesions.