Whole blood production of monocytic cytokines (IL-1β, IL-6, TNF-α, sIL-6R, IL-1Ra) in haemodialysed patients

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Abstract
Background. The production of monocytic cytokines by isolated mononuclear cells after stimulation by phytohaemagglutinin (PHA) and lipopolysaccharide (LPS) is generally increased in haemodialysed (HD) patients. We performed whole blood (WB) cultures to evaluate cytokine production by blood cells inside their complex cellular and humoral network. Methods. Diluted whole blood from HD patients (collected before dialysis) and controls was cultured alone with PHA (2.5 μg/ml) or LPS (1 and 3 μg/ml). Supernatants were collected after 24 and 48 h of culture, and concentrations of IL-1 β, IL-6, TNF-α, sIL-6R and IL-1Ra were determined by ELISA. Results. The low spontaneous production of IL-1β, IL-6 and TNF-α in both patients and controls was not significantly modified by PHA. The lower dose of LPS (1 μg/ml) induced a significant but lower increase in production of IL-1β, IL-6 and TNF-α in patients than in controls. In contrast, while it did not further increase their production in controls, the higher concentration of LPS (3 μg/ml) still increased their production in patients to the same level than in controls. The plasma concentrations of sIL-6R were higher in patients than in controls. In both groups, the sIL-6R concentration did not vary during the culture period whether the cells were stimulated or not with LPS or PHA. This suggests that the increased plasma levels of sIL-6R were not produced by blood cells. Despite a similar significant LPS and PHA induced production of IL-1Ra, the IL-1Ra/IL-1β ratio was always higher in patients than in controls. Conclusion. Monocytes from HD patients in WB cultures are hyporesponsive to PHA and LPS for their IL-1β, TNFα and IL-6 production in contrast to isolated monocytes that demonstrate signs of activation. If it reflects the in vivo situation it could partly explain the immune defect in uraemic and haemodialysed patients. Higher sIL-6R/IL-6 and IL-1Ra/IL-1β ratios could also participate to the complex immune disturbances of HD patients by reducing the biological activity of two cytokines playing a major role in the immune and inflammatory network.