title: Resident and pro-inflammatory macrophages in the colon represent alternative context-dependent fates of the same Ly6Chi monocyte precursors.
abstract: Macrophages (mφ) are essential for intestinal homeostasis and the pathology of inflammatory bowel disease (IBD), but it is unclear whether discrete mφ populations carry out these distinct functions or if resident mφ change during inflammation. We show here that most resident mφ in resting mouse colon express very high levels of CX3CR1, are avidly phagocytic and MHCII(hi), but are resistant to Toll-like receptor (TLR) stimulation, produce interleukin 10 constitutively, and express CD163 and CD206. A smaller population of CX3CR1(int) cells is present in resting colon and it expands during experimental colitis. Ly6C(hi)CCR2(+) monocytes can give rise to all mφ subsets in both healthy and inflamed colon and we show that the CX3CR1(int) pool represents a continuum in which newly arrived, recently divided monocytes develop into resident CX3CR1(hi) mφ. This process is arrested during experimental colitis, resulting in the accumulation of TLR-responsive pro-inflammatory mφ. Phenotypic analysis of human intestinal mφ indicates that analogous processes occur in the normal and Crohn's disease ileum. These studies show for the first time that resident and inflammatory mφ in the intestine represent alternative differentiation outcomes of the same precursor and targeting these events could offer routes for therapeutic intervention in IBD.
authors.affiliation: Centre for Immunobiology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, Scotland, UK.
authors.forename: C C
authors.initials: CC
authors.lastname: Bain
authors.forename: C L
authors.initials: CL
authors.lastname: Scott
authors.forename: H
authors.initials: H
authors.lastname: Uronen-Hansson
authors.forename: S
authors.initials: S
authors.lastname: Gudjonsson
authors.forename: O
authors.initials: O
authors.lastname: Jansson
authors.forename: O
authors.initials: O
authors.lastname: Grip
authors.forename: M
authors.initials: M
authors.lastname: Guilliams
authors.forename: B
authors.initials: B
authors.lastname: Malissen
authors.forename: W W
authors.initials: WW
authors.lastname: Agace
authors.forename: A McI
authors.initials: AM
authors.lastname: Mowat
mesh_terms: D000818:Animals; D000950:Antigens, Ly / Q000378:metabolism; D000073883:CX3C Chemokine Receptor 1; D002454:Cell Differentiation; D002465:Cell Movement; D049109:Cell Proliferation; D002478:Cells, Cultured; D003092:Colitis / Q000139:chemically induced / Q000276:immunology*; D003106:Colon / Q000276:immunology*; D000949:Histocompatibility Antigens Class II / Q000378:metabolism; D006801:Humans; D007249:Inflammation / Q000473:pathology; D015212:Inflammatory Bowel Diseases / Q000276:immunology*; D016753:Interleukin-10 / Q000378:metabolism; D008264:Macrophages / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009000:Monocytes / Q000276:immunology*; D054390:Receptors, CCR2 / Q000235:genetics / Q000378:metabolism; D019707:Receptors, Chemokine / Q000235:genetics / Q000378:metabolism
chemical_list: D000950:Antigens, Ly; D000073883:CX3C Chemokine Receptor 1; C515335:Ccr2 protein, mouse; C471885:Cx3cr1 protein, mouse; D000949:Histocompatibility Antigens Class II; C494192:Ly-6C antigen, mouse; D054390:Receptors, CCR2; D019707:Receptors, Chemokine; D016753:Interleukin-10