To investigate the effect of lipopoly~saccharide(LPS) and dialyzer membrane on cytokine gene expression and protein production in uremic patients on continuous ambulatory peritoneal dialysis(CAPD) and regular hemodialysis(HD) Methods Interleukin 1β(IL 1β) and interleukin 1 receptor antagonist(IL 1Ra) produced by cultured peripheral blood mononuclear cells(PBMC) after exposure to cuprammonium(Cup) membrane, polysulfone(PS) membranes or endotoxin were detected using enzyme linked immunoabsorbent assay mRNA expression was determined simultaneously by in situ hybridiztion Results In the absence of endotoxin, a small amount of IL 1β and IL 1Ra was produced by PBMC harvested from HD and CAPD patients after incubation with Cup or PS during subsequent 24 hour culture For healthy controls, IL 1β was barely detectable just above the detection limit Although no differences could be found in protein synthesis between Cup and PS, in situ hybridization showed that Cup induced markedly higher level mRNA coding for IL 1β and IL 1Ra In contrast, when subsequently stimulated with endotoxin, PBMC incubated with Cup could produce significantly larger amount of IL 1β and IL 1Ra compared with either unstimulated cells or post incubation PBMC with PS LPS stimulated PBMC in healthy subjects produced similar amount of IL 1β and markedly lower IL 1Ra as compared with uremic patients on HD and CAPD Conclusions Two steps are required in healthy control for IL 1β and IL 1Ra production: induction of mRNA transcription by membrane contact, followed by LPS induced translation, while in uremic patients on HD or CAPD bioincompatibility membrane and LPS have a synergetic effect on IL 1β and IL 1Ra production There exists an unbalance between IL 1β and its specific inhibitor in maintenance dialysis patients To investigate the effect of lipopoly-saccharide (LPS) and dialyzer membrane on cytokine gene expression and protein production in uremic patients on continuous ambulatory peritoneal dialysis (CAPD) and regular hemodialysis (HD) Methods Interleukin 1β (IL 1β) and interleukin 1 receptor antagonist (IL 1Ra) produced by cultured peripheral blood mononuclear cells (PBMC) after exposure to cuprammonium (Cup) membrane, polysulfone (PS) membranes or endotoxin were detected using enzyme linked immunoabsorption assay mRNA expression was determined by in situ hybridiztion Results In In absence of endotoxin, a small amount of IL 1β and IL 1Ra was produced by PBMC harvested from HD and CAPD patients after incubation with Cup or PS during subsequent 24 hour culture For healthy controls, IL 1β was barely detectable just above the detection limit Although no differences could be found in protein synthesis between Cup and PS, in situ hybridization showed that Cup in duced markedly higher level mRNA coding for IL 1β and IL 1Ra In contrast, when followed stimulated with endotoxin, PBMC incubated with Cup could produce significantly more IL 1β and IL 1Ra compared to either unstimulated cells or post incubated PBMC with PS LPS stimulated PBMC in healthy subjects contributed similar amount of IL 1β and markedly lower IL 1Ra as compared with uremic patients on HD and CAPD Conclusions Two steps are required in healthy control for IL 1β and IL 1 Ra production: induction of mRNA transcription by membrane contact, followed by LPS induced translation, while in uremic patients on HD or CAPD bioincompatibility membrane and LPS have a synergetic effect on IL 1β and IL 1Ra production There exists an unbalance between IL 1β and its specific inhibitor in maintenance dialysis patients