ULTRASTRUCTURAL RECOGNITION OF CELLS WITH DENDRITIC CELL MORPHOLOGY IN HUMAN AORTIC INTIMA - CONTACTING INTERACTIONS OF VASCULAR DENDRITIC CELLS IN ATHERO-RESISTANT AND ATHERO-PRONE AREAS OF THE NORMAL AORTA

Analysis of serial ultrathin sections of the human aortic intima detec ted a new cell yet to be described in the literature. These cells, whi ch we have designated Vascular Dendritic Cells, appeared in contact wi th each other and with other intimal cells. Vascular dendritic cells a re characterised by ultrastructural features similar to those of dendr itic cells, including a well developed smooth endoplasmic reticulum an d the presence of several processes which were 3-5 or more times in ex cess of the size of the cell body. In areas of the normal aorta resist ant to atherosclerosis, vascular dendritic cells were mainly localised in the subendothelial layer where they contacted both endothelial cel ls and smooth muscle cells. In areas of the normal aorta predisposed t o atherosclerosis, vascular dendritic cells were distributed throughou t the intima and the cellular interactions were altered with the vascu lar dendritic cells, developing multiple contacts with monocyte/macrop hages and lymphocyte-like cells. Aortic areas predisposed to atheroscl erosis showed the destruction of some vascular dendritic cell processe s where they apposed endothelial cells. We speculate that vascular den dritic cells (VDCs) are a variety of dendritic cell and are involved i n the maintenance of homeostasis in normal arterial intima. Vascular d endritic cells may be important in the development of atherosclerotic lesions, possibly through an immune mechanism.