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Immunity. 2013 Sep 19;39(3):599-610. doi: 10.1016/j.immuni.2013.08.007. Epub 2013 Sep 5.

Minimal differentiation of classical monocytes as they survey steady-state tissues and transport antigen to lymph nodes.

Author information

1
Department of Pediatrics at National Jewish Health, Denver, CO 80206, USA; Integrated Department of Immunology, University of Colorado, Denver, CO 80206, USA; Department of Gene and Cell Medicine, Mount Sinai School of Medicine, New York, NY 10029, USA.

Abstract

It is thought that monocytes rapidly differentiate to macrophages or dendritic cells (DCs) upon leaving blood. Here we have shown that Ly-6C⁺ monocytes constitutively trafficked into skin, lung, and lymph nodes (LNs). Entry was unaffected in gnotobiotic mice. Monocytes in resting lung and LN had similar gene expression profiles to blood monocytes but elevated transcripts of a limited number of genes including cyclo-oxygenase-2 (COX-2) and major histocompatibility complex class II (MHCII), induced by monocyte interaction with endothelium. Parabiosis, bromodoxyuridine (BrdU) pulse-chase analysis, and intranasal instillation of tracers indicated that instead of contributing to resident macrophages in the lung, recruited endogenous monocytes acquired antigen for carriage to draining LNs, a function redundant with DCs though differentiation to DCs did not occur. Thus, monocytes can enter steady-state nonlymphoid organs and recirculate to LNs without differentiation to macrophages or DCs, revising a long-held view that monocytes become tissue-resident macrophages by default.

PMID:
24012416
PMCID:
PMC3820017
DOI:
10.1016/j.immuni.2013.08.007
[Indexed for MEDLINE]
Free PMC Article

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