ULTRASTRUCTURAL EVIDENCE FOR ASSOCIATION OF VASCULAR DENDRITIC CELLS WITH T-LYMPHOCYTES AND WITH B-CELLS IN HUMAN ATHEROSCLEROSIS

It has been previously demonstrated that dendritic cells are involved in human atherogenesis and immunohistochemical analysis indicated that S100(+)/CD1a(+) vascular dendritic cells co-localize with lymphocytes in atherosclerotic lesions. Despite the high frequency of co-localiza tion of vascular dendritic cells and lymphocytes in cell-rich areas, d ifferent type intimal cells were often intermingled and very closely a pposed, which precluded determining whether vascular dendritic cells a nd lymphocytes specifically contacted each other or were simply densel y packed together. Therefore, we undertook the present electronmicrosc opical examination to see if vascular dendritic cells form direct cont acts with lymphocytes in human atherosclerotic lesions. Serial section ing of lymphocyte-rich areas of the human atherosclerotic aortas showe d that vascular dendritic cells exhibiting a well developed tubulovesi cular apparatus were located amongst T-lymphocytes and that through th eir processes, vascular dendritic cells formed multiple contacts with T-lymphocytes. In these contacts, vascular dendritic cell processes ex hibited hypertrophied cisterns of the tubulovesicular system, which su ggests the activation of vascular dendritic cells. From our observatio ns we speculate that vascular dendritic cells may be responsible for t he survival and activation of T-lymphocytes since a large number of T- lymphocytes which did not form contacts with vascular dendritic cells were found to have undergone destruction in atherosclerotic lesions. B -cells (plasma cells) were rarely seen in atherosclerotic lesions but vascular dendritic cells were found to form direct contacts with them. That vascular dendritic cells contact with both the T- and B-cells su ggests that these vascular dendritic cells differ from other dendritic cells, subtypes of which are associated with T-cells (Langerhans cell s, interdigitating cells) or with B-cells (follicular dendritic cells) .