Changes in CD14 expression on monocytes and changes in serum soluble CD14 level during hemodialysis

Background. CD14 is a receptor of lipopolysaccharide (LPS) and LPS binding protein (LBP) complex expressed on monocytes, and changes in the cell surface CD14 expression are thought to be a marker of activation of these cells. CD14 is shed from the cell surface when monocytes are activated. In this study, we assessed the influence of dialyzer membrane material and dialysate purity on monocyte CD14 expression and serum soluble CD14 (sCD14) levels in chronic hemodialysis (HD) patients in vivo during HD. Methods. We measured LPS concentrations in dialysate at two institutions by limulus assay. From one institution where LPS was undetectable in dialysate over a 2- year period, we selected seven patients. In the first period of the study, they were treated with a regenerated cellulose (RC) dialyzer, and then they were treated with a polysulfone (PS) dialyzer. We named them the 'RC group' and the 'PS group', respectively. From the other institution, where dialysate was contaminated with LPS, we selected eight patients. They were treated with a PS dialyzer, and were named the 'PS + LPS group'. CD14 expression on monocytes and serum sCD14 concentrations were measured by flow cytometry analysis and enzyme-liked immunosorbent assay, respectively. Results. During HD, in the RC group, upregulation of CD14 expression across the dialyzer was greater than in the PS group. There was no significant variation in serum sCD14 levels during HD in the RC and PS groups, while in the PS + LPS group, serum sCD14 level on the venous side of the dialyzer was significantly increased at 30 and 180 min after the initiation of HD compared with the predialysis value, and at 30 and 180 min compared with the level on the arterial side of the dialyzer. These results suggest that the changes in CD14 expression reflected the effect of dialyzer membrane material, while the changes in serum sCD14 levels reflected the effect of LPS influx from the dialysate. Conclusion. Dialysate purity may be an important factor in preventing monocyte activation during HD.