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C5a negatively regulates toll-like receptor 4-induced immune responses

Heiko Hawlisch, Yasmine Belkaid, Ralf Baelder, David Hildeman, Craig Gerard, Jörg Köhl*

*Corresponding author for this work

Abstract

The complement system and the Toll-like receptors (TLRs) are two central arms of innate immunity that are critical to host defense as well as the development of adaptive immunity. Most pathogens activate both complement and TLRs, suggesting the potential for crosstalk between the two systems. We show here that the complement-derived C5a anaphylatoxin negatively regulates TLR4- and CD40-induced synthesis of IL-12 family cytokines (IL-12, IL-23, and IL-27) from inflammatory macrophages (Mφs) by extracellular signal-regulated kinase- and phosphoinositide 3 kinase-dependent pathways. This decreased cytokine response translates into a decreased T helper type 1 (Th1) response in vitro and in vivo. Accordingly, we found enhanced Th1 immunity in C5a receptor-deficient mice, something that conferred protection from Leishmania major infection. Our findings identify the negative impact of C5a on IL-12 family cytokines as an important mechanism for regulating Th1 polarization in response to innate and adaptive immune network activation.

Original languageEnglish
JournalImmunity
Volume22
Issue number4
Pages (from-to)415-426
Number of pages12
ISSN1074-7613
DOIs
Publication statusPublished - 01.01.2005

Funding

We thank L.M. Flick for her help with the LAL assay and C.L. Karp for helpful discussions and critically reading the manuscript. This work was supported by Cincinnati Children’s Hospital Research Foundation funding (to J.K.). H.H. and R.B. were supported by Research Fellowships from Deutsche Forschungsgemeinschaft.

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

  1. SDG 3 - Good Health and Well-being
    SDG 3 Good Health and Well-being

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