Cytokine Modulation in Experimental Endotoxemia: Characterization of an ex vivo Whole Blood Model

Abstract

A new model was developed to study cytokine regulation and modulation in whole blood ex vivo. The model is characterized by stable leukocyte counts and high leukocyte viability throughout the experimental period. Oxygen consumption per time decreased slowly, whereas carbon dioxide partial pressure increased accordingly throughout the experiment. In this model, the anti-inflammatory effects of recombinant human (rh) interleukin (IL)-4, rhIL-10 and rhIL-13 on lipopolysaccharide (LPS) stimulated (10 ng/ml) leukocytes were examined and compared by measuring their ability to inhibit the release and mRNA levels of tumor necrosis factor (TNF)α, IL-6 and IL-1β. rhIL-10 potently inhibited the release of TNF-α, IL-6 and IL-1β in a potent and dose-dependent manner, but did not influence the mRNA levels of these cytokines in CD14-positive cells. Also, rhIL-4 and rhIL-13 inhibited the release of IL-6 and IL-1β in a potent and dose-dependent manner, however, stronger maximal inhibition of IL-1β (85%) than of IL-6 (60%) was obtained. In contrast, rhIL-4 and rhIL-13 seemed to have both stimulatory and inhibitory effects on plasma values of TNF-α. The effects of 10 ng/ml LPS showed to be signalling through the CD14 receptor, since blood treated with a monoclonal anti-CD14 antibody did not produce any TNF-α. The whole blood model described in this study is in our opinion a useful tool for investigating immunomodulating effects on a mixed white blood cell population.