Production of proinflammatory and regulatory monokines in hemodialysis patients shown at a single-cell level.

Immunologic complications of chronic renal failure are associated with the overproduction of proinflammatory cytokines by monocytes. This is partly due to renal failure itself but is further enhanced by hemodialysis treatment with frequent contact between blood and dialyzer membranes. Previous studies have shown an imbalance of proinflammatory and regulatory monokines in these patients. This study examines monokine production in hemodialysis patients using for the first time a very sensitive method of cytokine detection at a single-cell level by flow cytometry ("cytoflow technique"). Monocytes were stained intracellularly for the production of interleukin-6 (IL-6) and IL-10 after 20 h of culture with lipopolysaccharide. It was shown that high levels of proinflammatory IL-6 in hemodialysis patients are due to an increased number of monocytes producing this cytokine, while IL-6 synthesis per cell remains unchanged. In contrast, elevated levels of regulatory IL-10 are due to an increased synthesis per cell. This study demonstrates that in healthy subjects there is a population of monocytes producing exclusively IL-10 after 20 h of stimulation by lipopolysaccharide. This distinct population of regulatory monocytes is infrequent in dialysis patients, in whom most of the IL-10-positive monocytes also produce IL-6. These findings indicate that overproduction of proinflammatory factors in dialysis patients is at least in part due to a loss of cytokine-specific differentiation in monocytes.