Leukocyte adhesion molecules and leukocyte-platelet interactions during hemodialysis: effects of different synthetic membranes

Membranes made from synthetic polymers, in general, are considered as being biocompatible membranes and tend to be treated as a homogeneous group. How ever, all of these membranes have multiple and different characteristics th at may contribute to interactions with blood components. As a consequence, the biocompatibility profile of synthetic membranes may vary. In the presen t cross-over study, we examined by flow cytometry the effects (expressed as % change from predialysis values) of three different synthetic polymers (p olysulfone, PSF; polyacrylonitrile-co-sodium methallyl sulfonate, AN69; eth ylenevinylalcohol, EVAL) on the expression of leukocyte adhesion molecules (CD11b/CD18, CD15s) and the interactions between leukocytes and platelets u nder conditions of routine clinical use. For neutrophils, a statistically significant difference was found in CD15s expression for EVAL as compared to AN69 (p<0.05) and in CD11b/CD18 expressi on for PSF as compared to both EVAL (p<0.01) and AN69 (p<0.05). No differen ce between membranes was found on the expression of such adhesive molecules on monocytes. Significant differences in platelet-neutrophil (but not in p latelet-monocyte) coaggregate formation were observed between PSF and both EVAL (p<0.001) and AN69 (p<0.01). Reactive oxygen species production by neu trophil population during hemodialysis was significantly different between each pair of synthetic polymers (PSF vs EVAL, p<0.001; PSF vs AN69, p<0.001 ; AN69 vs EVAL, p<0.05). Our data demonstrate that in terms of leukocyte adhesion receptors and plat elet-leukocyte interactions, the biocompatibility profile of the synthetic membranes polysulphone, AN69 and EVAL shows many similarities but also seve ral significant differences. Our results support the concept that biocompat ibility evaluation of each membrane should be based exclusively on data gen erated by that membrane in order to avoid errors based on assumptions about group characteristics.