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Biological Chemistry

Editor-in-Chief: Brüne, Bernhard

Editorial Board Member: Buchner, Johannes / Ludwig, Stephan / Sies, Helmut / Turk, Boris / Wittinghofer, Alfred

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Complement Factor I Is Upregulated in Rat Hepatocytes by Interleukin-6 But Not by Interferon-γ , Interleukin-1β or Tumor Necrosis Factor-α

Gerald Schlaf / Thorsten Demberg / Milena Koleva / Kurt Jungermann / Otto Götze

Citation Information: Biological Chemistry. Volume 382, Issue 7, Pages 1089–1094, ISSN (Print) 1431-6730, DOI: 10.1515/BC.2001.137, June 2005

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Complement factor I (FI) is a regulatory serine protease of the complement system which cleaves three peptide bonds in the αchain of C3b and two bonds in the αchain of C4b and thus prevents the assembly of the C3 and C5 convertases. We have investigated the proinflammatory cytokines IL-6, IL-1β, TNFα and IFNγ for their potential role in the regulation of FI expression. Of the investigated cytokines, only IL-6 increased the FIspecific RTPCR signal in isolated hepatocytes, in the two rat hepatomaderived cell lines FAO and H4IIE or in HUVECs. Quantitative competitive RTPCR showed an IL-6 induced upregulation of FIspecific mRNA by about tenfold. These data are in accord with Northern blot analyses in which the FImRNA was upregulated by IL-6 between five and sevenfold. IL-6, but not IL-1β, TNFα or IFNγ also increased FIprotein levels in cell culture supernatants by about fivefold as determined by a semiquantitative immunoblot using a novel monoclonal antibody specific for rat FI.

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