Morphological aspects of endothelial cell-monocyte interactions in culture.

Monocytes obtained from the blood of healthy volunteers were added to cultures of bovine aortic endothelial cells (BAEC) at increasing time intervals (from 1 h to 24 h). Cultures of BAEC without the added blood elements were used as controls. The ultrastructural features of cellular interactions were studied by transmission electron microscopy. After 4 h, in the co-cultured endothelial cells focal cytoplasmic lesions appeared in the areas where activated monocytes were strictly in contact. Adhering monocytes frequently appeared apoptotic. After 24 h, pseudopod-like cytoplasmic projections originating from the endothelial cells gave rise to areas of close contact between the BAEC and the monocytes. These data reveal until now unknown endothelial cell taxis toward blood cells.