ADHERENCE OF SICKLE ERYTHROCYTES TO VASCULAR ENDOTHELIAL-CELLS - REQUIREMENT FOR BOTH CELL-MEMBRANE CHANGES AND PLASMA FACTORS

Abstract

Increased adherence of sickle red cells to vascular endothelium may initiate vasoocclusive events in sickle cell disease. A micropipette technique was developed to obtain direct, quantitative measure of the adherence of individual red cells to vascular endothelial cells. Using this technique, the vast majority of sickle cells suspended in autologous plasma were found to be strongly adherent to endothelial cells, whereas only a small fraction of normal cells were weakly adherent. Influence of plasma factors on adherence was determined by measuring adherence of sickle cells suspended in normal plasma and normal cells suspended in sickle plasma. Although over 90% of sickle cells adhered to endothelial cells in autologous plasma, the percentage of adherent cells decreased dramatically to < 20% when the same sickle cells were suspended in normal plasma. Adhesion of normal red cells suspended in sickle plasma was only modestly increased compared to adhesion in autologous normal plasma. Direct evidence was provided for markedly enhanced adherence of sickle cells to endothelial cells. Both cell membrane changes and plasma factors apparently contribute to this interaction. The requirement for sickle plasma further implies that temporal changes in plasma factors may play an important role in determining the onset of vasoocclusive crisis.