IL‐10 inhibits LPS‐induced human monocyte tissue factor expression in whole blood

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Abstract
Interleukin 4 (IL‐4), IL‐10 and IL‐13 are all known to modulate several proinflammatory functions in human monocytes. They have also previously been shown to down‐regulate lipopolysaccharide (LPS)‐induced tissue factor (TF) expression in isolated cultured monocytes. In this study we investigated the effect of these three cytokines on the induction of monocytic TF in a whole blood environment at three levels: mRNA quantitation, surface antigen expression and procoagulant activity. We showed that IL‐10 attenuated LPS‐induced monocyte TF expression and activity in whole blood in a concentration‐dependent manner, both when added to the blood prior to LPS and, although to a lesser extent, when added up to 1 h subsequent to LPS challenge. Maximum inhibition occurred at 5 ng/ml of IL‐10 when the cytokine was added before LPS. IL‐4 and IL‐13, however, did not exhibit any inhibitory effect in the whole blood environment, contrary to the reported findings in cell culture experiments. Our results confirm the potential of IL‐10 as an anti‐inflammatory, TF‐preventing drug, whereas the effects of IL‐4 and IL‐13 on monocytes in whole blood seem more complex, and require further investigation.