IL-10 is a potent anti-inflammatory cytokine and inhibitor of TNF-alpha production. The molecular pathways by which IL-10 inhibits TNF-alpha production are obscure, with diverse mechanisms having been published. In this study, a new approach has been taken for the study of human cells. Adenovirus was used to deliver TNF-alpha promoter-based luciferase reporter genes to primary human monocytic cells. The reporter genes were highly responsive to macrophage activation and appeared to mirror the behavior of the endogenous TNF-alpha gene. When added, either with or after the stimulus, IL-10 required the 3' untranslated region of the TNF-alpha gene to inhibit luciferase mRNA and protein expression, indicating a posttranscriptional mechanism. However, if macrophages were incubated with IL-10 before activation, inhibition of gene expression was also mediated by the 5' promoter, suggesting a transcriptional mechanism. To our knowledge, this is the first time that a dual mechanism for IL-10 function has been demonstrated. Studies to elucidate the mechanisms underlying the inhibition of TNF-alpha production addressed the effect of IL-10 on the activation of p38 mitogen-activated protein kinase and NF-kappaB. However, these studies could demonstrate no requirement for the inhibition of p38 mitogen-activated protein kinase or NF-kappaB activation as potential mechanisms. Overall, these results may explain the diversity previously ascribed to the complex mechanisms of IL-10 anti-inflammatory activity.

Original publication




Journal article


Journal of immunology (Baltimore, Md. : 1950)

Publication Date





4837 - 4845


Kennedy Institute of Rheumatology Division, Imperial College Faculty of Medicine, Charing Cross Campus, 1 Aspenlea Road, London, United Kingdom.


Cells, Cultured, Macrophages, Humans, Adenoviridae, Mitogen-Activated Protein Kinases, p38 Mitogen-Activated Protein Kinases, Lipopolysaccharides, Zymosan, Tumor Necrosis Factor-alpha, NF-kappa B, RNA, Messenger, 3' Untranslated Regions, 5' Untranslated Regions, Immunosuppressive Agents, Interleukin-10, Enzyme Inhibitors, Gene Expression Regulation, Enzyme Activation, RNA Stability, Genes, Reporter, Promoter Regions, Genetic