Interleukin-4 induces Coxiella burnetii replication in human monocytes but not in macrophages.
Coxiella burnetii, an obligate intracellular bacterium, is the agent of Q fever. The chronic disease is characterized by impaired cell-mediated immune response and microbicidal activity of monocytes. We hypothesized that interleukin(IL)-4, a Th2 cytokine, interferes with the fate of C. burnetii inside monocytes. C. burnetii survived without multiplication in resting monocytes, but replicated in IL-4-treated monocytes. The effect of IL-4 is specific for monocytes since IL-4 did not stimulate C. burnetii replication in monocyte-derived macrophages. The effects of IL-4 on bacterial replication and on tumor necrosis factor (TNF) production in monocytes were apparently not related. Although IL-4 inhibited C. burnetii-stimulated release of TNF, the addition of recombinant TNF to IL-4-treated monocytes did not prevent the IL-4 effect. These results suggest that IL-4 enables monocytes to support C. burnetii replication and a Th2 polarization of immune response that may interfere with immune control of Q fever.
Ghigo
Eric
E
Unité des Rickettsies, CNRS UMR 6020, IFR 48, Université de la Méditerranée, 13385 Marseille Cedex 05, France.
Imbert
Guenièvre
G
Capo
Christian
C
Raoult
Didier
D
Mege
Jean-Louis
JL
D002455:Cell Division / Q000187:drug effects; D016997:Coxiella burnetii / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D066298:In Vitro Techniques; D015847:Interleukin-4 / Q000494:pharmacology*; D007700:Kinetics; D007963:Leukocytes, Mononuclear / Q000382:microbiology*; D008264:Macrophages / Q000382:microbiology*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D014409:Tumor Necrosis Factor-alpha; D015847:Interleukin-4