Résumé
Macrophages play a central role in intestinal immunity, but inappropriate macrophage activation is associated with inflammatory bowel disease (IBD). Here, we identify granulocyte-macrophage colony stimulating factor (GM-CSF) as a critical regulator of intestinal macrophage activation in patients with IBD and mice with dextran sodium sulfate (DSS)-induced colitis. We find that GM-CSF drives the maturation and polarization of inflammatory intestinal macrophages, promoting anti-microbial functions while suppressing wound-healing transcriptional programs. Group 3 innate lymphoid cells (ILC3s) are a major source of GM-CSF in intestinal inflammation, with a strong positive correlation observed between ILC or CSF2 transcripts and M1 macrophage signatures in IBD mucosal biopsies. Furthermore, GM-CSF-dependent macrophage polarization results in a positive feedback loop that augmented ILC3 activation and type 17 immunity. Together, our data reveal an important role for GM-CSF-mediated ILC-macrophage crosstalk in calibrating intestinal macrophage phenotype to enhance anti-bacterial responses, while inhibiting pro-repair functions associated with fibrosis and stricturing, with important clinical implications.
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•ILCs are a major source of GM-CSF, a critical regulator of gut inflammatory macrophages•GM-CSF promotes ILC-macrophage crosstalk and augments type 17 and barrier immunity•GM-CSF-induced macrophages are protective during infection but drive inflammatory colitis•GM-CSF suppresses wound-healing macrophage response associated with intestinal fibrosis
Castro-Dopico et al. identify GM-CSF as a major upstream regulator of intestinal inflammatory macrophages, with ILC-derived GM-CSF polarizing macrophages toward a glycolytic, anti-microbial phenotype while suppressing wound-healing, pro-fibrotic activity. GM-CSF initiates further ILC-macrophage crosstalk, amplifying ILC3 activation and type 17 immunity.