Tissue-resident macrophage populations are maintained or expanded by local proliferation and, in nematode infection, this requires interleukin-4 (IL-4). This study shows that the expression of IL-4 receptor-α (IL-4Rα) by macrophages confers a competitive advantage, allowing higher and more sustained proliferation of IL-4Rα+ compared with IL-4Rα− resident macrophages. Early during nematode infection, proliferation is IL-4Rα independent and is controlled by colony-stimulating factor 1 (CSF1). As the immune response progresses, proliferation and alternative activation become dependent on IL-4. The authors suggest that the IL-4 pathway allows the outgrowth of resident macrophages when CSF1 is limiting without a coincident increase in monocyte recruitment.
References
Jenkins, S. J. et al. IL-4 directly signals tissue-resident macrophages to proliferate beyond homeostatic levels controlled by CSF-1. J. Exp. Med. http://dx.doi.org/10.1084/jem.20121999 (2013)
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Bird, L. Interleukin-4 boosts macrophage numbers. Nat Rev Immunol 13, 775 (2013). https://doi.org/10.1038/nri3555
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DOI: https://doi.org/10.1038/nri3555