IFN-γ priming of macrophages represses a part of the inflammatory program and attenuates neutrophil recruitment

MA Hoeksema, BP Scicluna, M Boshuizen… - The Journal of …, 2015 - journals.aai.org
The Journal of Immunology, 2015journals.aai.org
Macrophages form a heterogeneous population of immune cells, which is critical for both the
initiation and resolution of inflammation. They can be skewed to a proinflammatory subtype
by the Th1 cytokine IFN-γ and further activated with TLR triggers, such as LPS. In this work,
we investigated the effects of IFN-γ priming on LPS-induced gene expression in primary
mouse macrophages. Surprisingly, we found that IFN-γ priming represses a subset of LPS-
induced genes, particularly genes involved in cellular movement and leukocyte recruitment …
Abstract
Macrophages form a heterogeneous population of immune cells, which is critical for both the initiation and resolution of inflammation. They can be skewed to a proinflammatory subtype by the Th1 cytokine IFN-γ and further activated with TLR triggers, such as LPS. In this work, we investigated the effects of IFN-γ priming on LPS-induced gene expression in primary mouse macrophages. Surprisingly, we found that IFN-γ priming represses a subset of LPS-induced genes, particularly genes involved in cellular movement and leukocyte recruitment. We found STAT1-binding motifs enriched in the promoters of these repressed genes. Furthermore, in the absence of STAT1, affected genes are derepressed. We also observed epigenetic remodeling by IFN-γ priming on enhancer or promoter sites of repressed genes, which resulted in less NF-κB p65 recruitment to these sites without effects on global NF-κB activation. Finally, the epigenetic and transcriptional changes induced by IFN-γ priming reduce neutrophil recruitment in vitro and in vivo. Our data show that IFN-γ priming changes the inflammatory repertoire of macrophages, leading to a change in neutrophil recruitment to inflammatory sites.
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