Granulocyte adhesion to endothelium in culture.

We previously described a model system for studying the adherence of granulocytes to cultured endothelium, and have now investigated the effects of other blood components on granulocyte adhesion in this system. Red cells enhanced adhesion, whereas blood platelets decreased adhesion, and further experiments suggested that endothelial cells secrete a proadhesive factor, particularly if incubated with plasma. We have also investigated the effects of several drugs, and attempted to localize their sites of action. Flavonoid drugs increased adhesion by an effect at the endothelial cell surface, whereas agents that increase cyclic AMP levels, including several prostaglandins, stimulated adhesion mainly by their effects on granulocytes. The effects of some agents on granulocyte adhesion to endothelium were not paralleled by their effects on adhesion to serum-coated glass. We conclude that granulocyte-endothelial interaction is a complex process, with each cell type responding to the other or to factors produced by it, and that data derived solely from studies of granulocyte adhesion to inert substrata will not always reflect granulocyte-endothelial interaction in vivo.