Modulation of erythrocyte-endothelial interactions and the vasocclusive severity of sickling disorders

The abnormal adherence of sickle erythrocytes to cultured human vascular endothelium varies among patients and correlates with vasocclusive severity within and among the different sickling disorders. For individual patients, the development of an acute vasocclusive event is not accompanied by an increase in the inherent propensity for their erythrocytes to adhere to endothelium. However, the onset of vasocclusion appears to be associated with the appearance of plasma factors, such as fibrinogen, which enhance the adherence of sickle erythrocytes to endothelium. In addition, sickle erythrocytes adhere even more avidly to injured endothelium and under hyperosmolar conditions. Thus, the overall clinical severity of the sickling disorders appears to correlate with the inherent propensity for sickle erythrocytes to adhere to endothelium, and changes in the red cells' environment may help precipitate crises by the sudden facilitation of erythrocyte/endothelial interactions.