Effect of two different dialysis membranes on leukocyte adhesion and aggregation

We evaluated modifications in formation of heterotypic platelet-leukocyte aggregation induced by dialysis through cellulosic or synthetic membranes and evaluated the effects of such procedures promoting adhesive interactions between leukocytes and normal endothelial cells (ECs).

Samples were obtained from arterial and venous lines at baseline, after 15 and 120 min of hemodialysis. Heterotypic aggregation was assessed using flow-cytometric techniques. Experiments to determine leukocyte adhesion to ECs were performed in parallel plate perfusion chambers at 450 s(-1).

Patients dialyzed with a cellulosic membrane showed a significantly higher baseline granulocyte heterotypic aggregation (median 22.5%, range 8.6-32%) versus healthy subjects (median 10%, range 3.2-14.6%; p < 0.05). Granulocyte heterotypic aggregation values remained increased throughout the hemodialysis session not only in the arterial line (median 18 and 24.5%, range 7-30 and 8.7-36% at 15 and 2 h, respectively) but also in the venous line (median 20 and 25%, range 8.6-32 and 11.5-35% at 15 min and 2 h, respectively). Basal lymphocytes heterotypic aggregation values observed in uremic patients were 6% (0.1-7.1%) versus 1.0% (0.5-2.8%) in the control group (p < 0.05). The increase remained during the hemodialysis session both in the arterial line (median 5 and 4%, range 0.2-14 and 0.5-7.1 % at 15 min and 2 h, respectively) and in the venous line (median 7 and 7%, range 1.4-14 and 0.5-10.6% at 15 min and 2 h). In contrast, patients dialyzed with a synthetic membrane showed a decreased basal granulocyte heterotypic aggregation compared to healthy subjects (median 3.5 vs. 10%, range 2.8-7 vs. 3.2-14.6%, respectively; p < 0.05). For lymphocytes, basal heterotypic aggregation values were 0.2% (range 0.1-0.5%) in dialyzed patients vs. 0.98% (range 0.5-2.8%) in healthy subjects (p < 0.05), without changes throughout the dialysis session. Changes in leukocyte adhesion during hemodialysis did not reach statistical significance with either hemodialysis membrane. Our studies confirm a differential activation of platelets and leukocytes depending on the nature of the dialysis membranes. However, activation of circulating cellular elements by hemodialysis procedures did not enhance cross-talk interactions between leukocytes and unaltered ECs.