Mononuclear leucocyte function tests in the assessment of the biocompatibility of peritoneal dialysis fluids

Background-Previous studies showed that the currently used dextrose based p eritoneal dialysis fluids impair several leucocyte functions. Aims-To determine which in vitro mononuclear leucocyte (monocyte) function tests most clearly reflect the biocompatibility of peritoneal dialysis flui d. Methods-Monocytes were tested for phagocytic capacity, bactericidal activit y, Fc and C3 receptor expression, and chemiluminescence response, and by an alysis of the release of interleukin 8 (IL-8) and tumour necrosis factor a (TNF alpha) in the presence of test fluids. Cytokine release was studied in an alternative dynamic in vitro peritoneal dialysis model in which monocyt es were exposed to test fluid that was continuously equilibrated with an in terstitial fluid-like medium through a microporous membrane. The chemilumin escence response by stressed monocytes was also tested after an 18 h recove ry period. All tests were performed during or after exposure to different d egrees of glycerol induced osmotic stress and after exposure to a 1% milk-w hey derived, polypeptide enriched test fluid. Cells incubated in 0.1% gel H anks buffer (GH) served as control. Results-Osmotic stress induced impairment of leucocyte function was found b y the chemiluminescence assay (mean (SEM): 179 (20)% v 138 (23)% after 30 0 .5% and 1.5%,glycerol, respectively) and by the analysis of IL-8 released b y monocytes (44 (9) ng in 0.7% glycerol v 40 (7) ng in 2.0% glycerol). Only the chemiluminescence assay showed a protective effect of polypeptides on leucocyte function (after greater than or equal to 60 minutes). If monocyte s were allowed to recover in culture medium after exposure to test fluids, the changes in chemiluminescence response appeared to be reversible after a 30 minute exposure, but became more pronounced after 60 and 120 minutes. T he phagocytosis and bacterial killing assays were less sensitive. The obser vations carried out with the phagocytosis assay did not correspond with the Fc or C3 receptor density data. Conclusions-The release of IL-8 by peripheral blood monocytes in a two comp artment model and their chemiluminescence response are appropriate assays f or the assessment of changes in leucocyte function in response to different peritoneal dialysis fluids.