Erythrocyte-endothelial cell adherence in senescence and in hemolytic disorders

Adherence of normal human erythrocytes to cultured endothelial cells when exposed to in vitro fluid shear forces typical of venules, capillaries and arterioles is very low, less than 0.03 percent, in the presence of an albumin-buffer but increases five fold by the effects of autologous plasma. Senescent erythrocytes obtained by density separation had an adherence frequency in the normal cell range, suggesting that predisposition to endothelial adherence is not a key factor in regulation of life span by the sequestration, identification and phagocytosis modulated by immune recognition. Sickle cells' frequency of adherence exceeds that of normal cells particularly at low shear forces calculated to resemble those of veins and sinuses, and increases five to ten fold when autologous plasma obtained during sickle crisis is present; these findings add support to the hypothesis that excessive tendency for sickle cell adherence may contribute to the vascular obstructive phenomena of the disorder. The behavior of hereditary spherocytes and thalassemic erythrocytes resembles normal cells, suggesting that hemolytic mechanisms are not significantly dependent on erythrocyte-endothelial cell interaction. Erythrocytes from patients having diabetes exhibit the characteristics of control cells, suggesting that their membrane adhesion to endothelium may not be critical to initiation of vessel wall pathophysiological processes; however, the behavior in relation to damaged endothelial cells may differ importantly.