Article

Minimal Differentiation of Classical Monocytes as They Survey Steady-State Tissues and Transport Antigen to Lymph Nodes

Department of Gene and Cell Medicine, Mount Sinai School of Medicine, New York, NY 10029, USA.
Immunity (Impact Factor: 19.75). 09/2013; 39(3). DOI: 10.1016/j.immuni.2013.08.007
Source: PubMed

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.

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Available from: Claudia Jakubzick, Aug 27, 2015
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    • "APCs of the MPS appear to have commensurate increased expression of antigen presentation and co-stimulatory molecules, and are potent secretors of modulatory cytokines[12]. They are motile, and in other tissues have been shown to express chemokine receptors which facilitate their transit to draining lymph nodes, prime naïve T cells and establish a systemic immune response [13] [14] [15]. "
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    ABSTRACT: The mononuclear phagocytic system (MPS), comprised of monocyte, macrophage and dendritic cells, is essential in tissue homeostasis and in determining the balance of the immune response through its role in antigen presentation. It has been identified as a therapeutic target in infectious disease, cancer, autoimmune disease and transplant rejection. Here we review the current understanding of the immunophenotype and function of the MPS in normal human liver. Using well-defined selection criteria, a search of MEDLINE and EMBASE databases identified 76 appropriate studies. The majority (n=67) described Kupffer Cells (KC), although the definition of KC differs between sources, and little data were available regarding their function. Only 10 papers looked at liver dendritic cells (DC), and largely confirmed the presence of the major dendritic cell subsets identified in human blood. Monocytes were thoroughly characterized in four studies that utilized flow cytometry and fluorescent microscopy and highlighted their prominent role in liver homeostasis and displayed subtle differences from circulating monocytes. There was some limited evidence that liver DC are tolerogenic but neither liver dendritic cell subsets nor macrophages have been thoroughly characterized using either multi-colour flow cytometry or multi-parameter fluorescence microscopy. The lobular distribution of different subsets of liver MPS cells was also poorly described, and the ability to distinguish between passenger leukocytes and tissue resident cells remains limited. It was apparent that further research using modern immunological techniques is now required to accurately characterise the cells of the MPS in human liver.
    Journal of Hepatology 10/2014; 62(2). DOI:10.1016/j.jhep.2014.10.006 · 10.40 Impact Factor
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    • "However, as no functional or mechanistic link has been reported thus far for this subset in mice, one needs to be careful with speculations on the conversion of murine classical into non-classical monocytes. Moreover, in a very recent study, Jakubzick and colleagues proved in a series of elegant experiments that classical monocytes might retain their phenotypic properties without differentiation under non-inflammatory conditions [19]. Future studies need to provide more detailed phenotypic and functional characteristics and lineage commitment and to elucidate pathophysiological roles of intermediate monocytes in the mouse [20]. "
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    ABSTRACT: Aims Mouse models of myocardial infarction (MI) are commonly used to explore the pathophysiological role of the monocytic response in myocardial injury and to develop translational strategies. However, no study thus far has examined the potential impact of inter-individual variability and sham surgical procedures on monocyte subset kinetics after experimental MI in mice. Our goal was to investigate determinants of systemic myeloid cell subset shifts in C57BL/6 mice following MI by developing a protocol for sequential extensive flow cytometry (FCM). Methods and Results Following cross-sectional multiplex FCM analysis we provide for the first time a detailed description of absolute quantities, relative subset composition, and biological variability of circulating classical, intermediate, and non-classical monocyte subsets in C57BL/6 mice. By using intra-individual longitudinal measurements after MI induction, a time course of classical and non-classical monocytosis was recorded. This approach disclosed a significant reduction of monocyte subset dispersion across all investigated time points following MI. We found that in the current invasive model of chronic MI the global pattern of systemic monocyte kinetics is mainly determined by a nonspecific inflammatory response to sham surgery and not by the extent of myocardial injury. Conclusions Application of sequential multiplexed FCM may help to reduce the impact of biological variability in C57BL/6 mice. Furthermore, the confounding influence of sham surgical procedures should always be considered when measuring monocyte subset kinetics in a murine model of MI.
    PLoS ONE 06/2014; 9(6):e98456. DOI:10.1371/journal.pone.0098456 · 3.23 Impact Factor
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    • "Depending on the tissue type and specific micro-environmental signals, these monocyte subsets give rise to functionally distinct subsets of DC or macrophage cells or OCs [11] [12] [13] as illustrated in Figure 1, which is based on the collective evidences from both mouse and human studies. Unusually, under steady state, classical monocytes may not differentiate into tissue macrophages or DCs, but may involve in surveillance of non-immune tissues to transfer the antigen information to the lymph node [14]. To unravel the molecular differences between these three subsets, various groups have performed global expression analysis in human [6, 8, 15–18]. "
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    ABSTRACT: Classical and non-classical monocytes are two well-defined subsets of monocytes displaying distinct roles. They differentially express numerous genes relevant to their primary role. Using five independent transcriptomic microarray datasets, we ruled out several inconsistent genes and identified common genes consistently overexpressed either in classical or non-classical monocytes. One hundred and eight genes were significantly increased in classical monocytes and are involved in bacterial defense, inflammation and atherosclerosis. Whereas the 74 genes overexpressed in non-classical monocytes are involved in cytoskeletal dynamics and invasive properties for enhanced motility and infiltration. These signatures unravel the biological functions of monocyte subsets. HIGHLIGHTS We compared five transcriptomic GEO datasets of human monocyte subsets. 108 genes in classical and 74 genes in non-classical monocytes are upregulated. Upregulated genes in classical monocytes support anti-bacterial and inflammatory responses. Upregulated genes in non-classical monocytes support patrolling and infiltration functions.
    International Reviews Of Immunology 04/2014; 33(6). DOI:10.3109/08830185.2014.902453 · 5.28 Impact Factor
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