Polymorphonuclear cell phagocytosis and surface receptor modulation after extracorporeal circulation

Polymorphonuclear cells (PMN) from patients treated with hemodialysis (HD) or plasma exchange (PE) were analyzed by flow cytometry to determine modulation in phagocytic capacity and Fc-gamma and C3bi receptor expression following extracorporeal circulation (EC). Fluorescent microbeads (phi 2.02 m) were used in the evaluation of phagocytosis, and phycoerythrin conjugated Leu11c and Leu15 monoclonals identified Fc-gamma and C3bi receptors respectively. The percentage of positive cells and mean receptor density on PMN surfaces were calculated for each antibody before and after the procedures. Fc-gamma receptor expression was reduced overall in HD and PE cases, but unaffected after EC even with specific paraprotein removal. C3bi receptor was normally expressed on PMNs before and after EC, but receptor density on the cell surface increased, and phagocytosis was qualitatively and quantitatively depressed after EC. The resulting effect of EC on PMNs was therefore a temporary increase in C3bi receptor density after the procedure, which was independent of HD or PE technique, of the primary disease, and of the quality of the PE reinfusion solutions, suggesting a procedure-related effect, and a down-regulation of PMN phagocytic activity. Both effects may be related to membrane biocompatibility.