Production of platelet activating factor by human neutrophils after backfiltration of endotoxin contaminated dialysate.

Lipopolysaccharide (LPS) from gram negative bacteria has been shown to prime human polymorphonuclear neutrophil (PMN) production of platelet activating factor (PAF). PAF is a lipid mediator of inflammation and endotoxic shock and is also involved in leukocyte activation occurring during hemodialysis; PAF induces leukopenia, degranulation of lysosomal granules, and adherence to hemodialysis membranes. Transmembrane passage of LPS has also been shown to occur. To evaluate the relevance of transmembrane passage of LPS on the priming of PMN derived production of PAF, we designed in vitro studies using an experimental circuit equipped with different membranes (Cuprophan, polysulfone, polymethylmethacrylate, polyamide) and recirculation of purified human PMNs. At different time intervals, PMNs were stimulated with FMLP (10 microM) after back-filtration of sterile and LPS contaminated dialysate. The results of these studies suggest that priming of PMN derived production of PAF was related to the percent of backfiltered LPS, and they emphasize the need for careful assessment of microbiologic quality to improve biocompatibility.