The measurement of cytokine production capacity during dialysis - a new dynamic method for the evaluation of biocompatibility?

The activation of monocytes and other immunocompetent cells during hemodial ysis can be attributed to their contact with immunogenic structures such as membranes, blood lines, and endotoxins. The simple measurement of cytokine s in blood cannot completely describe the whole dimension of this event. St imulation of monocytes and other immunocompetent cells in whole blood with lipopolysaccharides (LPS) for IL-6 and phytohemagglutinine (PHA) for TNF at the start and end of dialysis may make it possible to better analyze cellu lar response during dialysis. Ten healthy volunteers and 10 patients suffer ing from chronic renal failure were tested with the commercial whole-blood stimulation assays "Dynamix"-IL-6-DIA and -TNF-alpha-DIA (Biosource Diagnos tics, Ratingen, Germany). Then 24 patients undergoing hemodialysis with hem ophane (n=12) and polyamide (n=12) membranes were examined before and after dialysis treatment. The unpaired Wilcoxon t- test was used for statistical analysis. Healthy volunteers and patients with chronic renal failure showe d no statistical differences in concentrations of TNF-alpha and IL-6 before or after whole blood stimulation (WBS). In comparison to patients with chr onic renal failure, pre-WBS concentrations of both cytokines (p<0.034) were increased in patients of each membrane group before dialysis. After whole blood stimulation, no differences were observed At the end of dialysis trea tment, the pre- and post-WBS IL-6 values were both significantly higher in the hemophane group (p=0.049 and p=0.0038, respectively) TNF-alpha concentr ations were unchanged. No significant differences in the polyamide group we re found between the start and end of treatment for either cytokine. A comp arison of these membrane groups showed that only the pre-WBS IL-6 concentra tion in the hemophane group was elevated (p=0.022) after dialysis. In concl usion, the presence of uremia alone could not influence the cytokine produc tion and release capacity. In our patients, dialysis elevated pre-WBS conce ntrations of TNF-alpha and IL-6, and increased IL-6 release from immunocomp etent cells after whole blood stimulation in the hemophane group. The use o f polyamide membranes decreased the action of monocytes and other immunocom petent cells, but could not completely prevent this phenomenon. The whole b lood stimulation assays for measurement of TNF-alpha and IL-6 may represent a new, dynamic method for evaluating biocompatibility.