Identifying Friend or Foe - Mreg?

How do the immune cells within the gut distinguish between potentially dangerous pathogens and harmless or beneficial commensal organisms? [Hint: It’s not through PAMPs (pathogen-associated molecular patterns.)]

These investigators identified in mice a novel population of macrophages within the lamina propria, the layer of mucosa beneath the epithelium on the lumenal side of the intestine wall. These macrophages secrete IL-10 and other anti-inflammatory cytokines but no pro-inflammatory cytokines (even when stimulated through their Toll-like receptors by PAMPs). They also stimulate the development of regulatory T cells (Tregs) more potently than splenic macrophages (figure, CD4+ FoxP3+ Treg) and suppress the secretion of IL-17 by DC within the lamina propria. The authors suggest that a “dynamic interaction between these subsets may influence the balance between immune activation and tolerance”. They need to abbreviate the idea... how about 'Mregs'?

Denning et al. "Lamina propria macrophages and dendritic cells differentially induce regulatory and interleukin 17-producing T cell responses". Nat Immunol. 2007 Oct;8(10):1086-94.