Immunohistochemical and ultrastructural evidence that dendritic cells infiltrate stenotic aortocoronary saphenous vein bypass grafts

We earlier speculated that antigen-presenting dendritic cells may be involv ed in the immune reactions leading to saphenous vein bypass graft failure. The purpose of this study was to confirm whether dendritic cells are presen t in stenotic human saphenous vein bypass grafts. Segments of stenotic saph enous vein grafts were explanted from 14 patients at re-do bypass operation and ten normal saphenous veins were harvested during femoro-popliteal graf ting. Sections of specimens were analysed using cell type specific antibodi es to identify dendritic cells (CD1a, S-100), T-lymphocytes (CD3), macropha ges (CD68), smooth muscle cells (alpha -SMA) and endothelial cells (FVIII). Dual immunostaining, confocal immunofluorescent laser scanning microscopy and electron microscopy were used. Stenotic grafts showed structural altera tions of intimal hyperplasia and varying degrees of atherosclerotic degener ation, No cells expressing CD1a and S-100 were observed in the intima and m edia of normal saphenous veins. Cells expressing these antigens were presen t around areas of medial neovascularization and within intimal atherosclero tic lesions in saphenous vein bypass grafts. Electron microscopy demonstrat ed the presence of cells containing a well-developed tubulovesicular system which is unique to cells from the dendritic cell family, Double immunohist ochemistry and confocal immunofluorescent microscopy revealed the co-locali zation of T-lymphocytes with dendritic cells. Dendritic cells are present i n stenotic saphenous vein bypass grafts. Dendritic cells may be responsible for antigen presentation and modulation of immune reactions in accelerated graft atherosclerosis through their interaction with T-lymphocytes, (C) 20 01 The International Society for Cardiovascular Surgery. Published by Elsev ier Science Ltd, All rights reserved.