The effect of renal function on cytokine secretion capacity of mononuclear cells was analysed in patients who had not been subjected to any form of renal replacement therapy. The aim of the study was especially to determine whether there is a defect of monocyte function. The patients were divided into three groups of 12 on the basis of renal function: group I, serum creatinine 1.5-3 mg/dl; group II, 3-6 mg/dl; and group III, > 6 mg/dl. Serving as controls were 36 age- and sex-matched healthy volunteers. IL-1 beta, IL-6, TNF-alpha, IL-2 and IF-gamma concentrations were measured in the supernatants of stimulated and unstimulated cells isolated from the blood. Renal function was not found to have any effect on the secretion capacity of IL-2 and IF-gamma. However, the secretion capacity of IL-1 beta of lipopolysaccharide (LPS)-stimulated monocytes was reduced in patients of group III to 214 +/- 290 pg/ml, compared with 501 +/- 327 pg/ml in controls (P = 0.047). The effect was even more accentuated for IL-6 (group III: 5422 +/- 5116 pg/ml; controls: 16,319 +/- 12,474 pg/ml; P = 0.019). Spontaneous secretion levels did not change for any of the cytokines, and LPS-stimulated TNF-alpha secretion was also normal. Highly purified blood monocytes/macrophages were stained for CD14, HLA-DR, CD11c, and CD4. Neither the percentage of positive cells nor the fluorescence intensity, as measured by FACS, was influenced by renal function, and no correlation could be established between function and phenotype.(ABSTRACT TRUNCATED AT 250 WORDS)