Analysis of standard
Ficoll-
Hypaque (density = 1.077 g/ml) separation profiles of peripheral white blood cells (WBC) from patients undergoing
hemodialysis (HD) demonstrated that dialysis caused a marked decrease in the density of polymorphonuclear leukocytes (PMN) resulting in about 50% of these cells separating with the mononuclear cells. In vitro exposure of normal control peripheral blood to HD membranes as well as to the purified
chemotactic factors C5a, C5ades-Arg, and formyl-
Met-Leu-Phe (fMLP) also resulted in PMN density changes which altered the
Ficoll-
Hypaque separation profiles of WBC. Therefore, these results imply that C5a generation, resulting from complement activation by the HD membrane, induced the density changes in the PMN from HD patients. Further studies using flow cytometry and
fluorescein-labeled
chemotactic factors (C5a, formyl-
Met-Leu-Phe-Lys [
fMLPL] and
casein) indicated that HD patients had a significant reduction in the ability of their PMN and monocytes to bind C5a. This contrasted with the findings of no significant difference in the percentage or fluorescence intensity of HD patients' PMN or monocytes binding
casein or
fMLPL. Functional studies to analyze
chemotactic-factor-mediated responses indicated that there was a decreased ability of HD patients' PMN and monocytes to generate
superoxide anion, produce H2O2 and release
myeloperoxidase in response to both C5a and fMLP. Additional studies evaluated the binding of
chemotactic factors to PMN and monocytes from normal blood following passage through a
hemodialyzer and from patients undergoing HD. Analysis of receptor binding by control cells passed through the dialyzer showed that there was a progressive decrease in the percentage of C5a-receptor-positive PMN and monocytes but no change with
casein or
fMLPL. In contrast, peripheral PMN and monocytes from
chronic renal failure patients on HD showed no difference in C5a,
casein or
fMLPL receptors during the course of HD as compared to the predialysis period. This appears to be attributable to a difference in the regulation of the C5a that is generated as a result of the dialysis-membrane-induced activation of the
complement system. Although C5a has been shown to be continuously generated during the course of HD, these patients show no modulation of their
C5a receptors during the course of HD or when their whole blood is exposed to dialysis membrane fibers. These findings suggest that there are mechanisms functioning in chronically dialyzed patients to protect them from the effects of excessive C5a generation during HD.(ABSTRACT TRUNCATED AT 400 WORDS)