Clinical manifestations and erythrocyte adhesion to endothelium in sickle cell syndrome

Painful vasocclusive episodes are one of the most prominent pathological features of sickle cell disease. In addition to abnormal shape and poor deformability, increased adhesion of red cells to endothelium has been reported. On several occasions, we have studied the adhesion of erythrocytes from 30 patients with mixed sickle cell syndromes to evaluate the influence of clinical conditions. The percentage of erythrocytes adhering was significantly higher when erythrocytes from sickle patients were compared with controls (p < 0.01). Furthermore, adhesion was significantly higher when the patients were in crises (p < 0.01), and the highest values of all were observed in patients with inflammatory conditions. To investigate the possibility that a limited population of red cells could be responsible for the increase in red cell adhesion, we have measured the HbS concentration in the different washes and found that the HbS concentration was higher in the last washes compared to the first washes. Sickle red cells capable of protein synthesis (young red cells) were labelled with [3H] leucine. The adhesion to endothelial cells of [3H] leucine-labelled red cells was higher than that of the 51Cr-labelled red cells from the same patient. On the other hand, the most dense sickle red cells separated by density gradient adhered to a greater extent than the light red cells. This apparent discrepancy could be partly explained by the presence of [3H] leucine-labelled red cells in the dense fractions of sickle red cells separated by stractan gradient.