A flow cytometry approach reveals heterogeneity in conventional subsets of murine renal mononuclear phagocytes.

Mononuclear phagocytes (MNPs) participate in inflammation and repair after kidney injury, reflecting their complex nature. Dissection into refined functional subunits has been challenging and would benefit understanding of renal pathologies. Flow cytometric approaches are limited to classifications of either different MNP subsets or functional state. We sought to combine these two dimensions in one protocol that considers functional heterogeneity in each MNP subset. We identified five distinct renal MNP subsets based on a previously described strategy. In vitro polarization of bone marrow-derived macrophages (BMDM) into M1- and M2-like cells suggested functional distinction of CD86 + MHCII + CD206- and CD206 + cells. Combination of both distinction methods identified CD86 + MHCII + CD206- and CD206 + cells in all five MNP subsets, revealing their heterologous nature. Our approach revealed that MNP composition and their functional segmentation varied between different mouse models of kidney injury and, moreover, was dynamically regulated in a time-dependent manner. CD206 + cells from three analyzed MNP subsets had a higher ex vivo phagocytic capacity than CD86 + MHCII + CD206- counterparts, indicating functional uniqueness of each subset. In conclusion, our novel flow cytometric approach refines insights into renal MNP heterogeneity and therefore could benefit mechanistic understanding of renal pathology.

Determining the effector response to cell death.

Cell death occurs when a pathogen invades a host organism or the organism is subjected to sterile injury. Thus, cell death is often closely associated with the induction of an immune response. Furthermore, cell death can occur as a consequence of the immune response and precedes the tissue renewal and repair responses that are initiated by innate immune cells during resolution of an immune response. Beyond immunity, cell death is required for development, morphogenesis and homeostasis. How can such a ubiquitous event as cell death trigger such a wide range of context-specific effector responses? Dying cells are sensed by innate immune cells using specialized receptors and phagocytosed through a process termed efferocytosis. Here, we outline a general principle whereby signals within the dead cell as well as the environment are integrated by specific efferocytes to define the appropriate effector response.

Hemolysis transforms liver macrophages into antiinflammatory erythrophagocytes.

During hemolysis, macrophages in the liver phagocytose damaged erythrocytes to prevent the toxic effects of cell-free hemoglobin and heme. It remains unclear how this homeostatic process modulates phagocyte functions in inflammatory diseases. Using a genetic mouse model of spherocytosis and single-cell RNA sequencing, we found that erythrophagocytosis skewed liver macrophages into an antiinflammatory phenotype that we defined as MarcohiHmoxhiMHC class IIlo erythrophagocytes. This phenotype transformation profoundly mitigated disease expression in a model of an anti-CD40-induced hyperinflammatory syndrome with necrotic hepatitis and in a nonalcoholic steatohepatitis model, representing 2 macrophage-driven sterile inflammatory diseases. We reproduced the antiinflammatory erythrophagocyte transformation in vitro by heme exposure of mouse and human macrophages, yielding a distinctive transcriptional signature that segregated heme-polarized from M1- and M2-polarized cells. Mapping transposase-accessible chromatin in single cells by sequencing defined the transcription factor NFE2L2/NRF2 as a critical driver of erythrophagocytes, and Nfe2l2/Nrf2 deficiency restored heme-suppressed inflammation. Our findings point to a pathway that regulates macrophage functions to link erythrocyte homeostasis with innate immunity.

Mononuclear phagocyte subpopulations in the mouse kidney.

Mononuclear phagocytes are the most common cells in the kidney associated with immunity and inflammation. Although the presence of these cells in the kidney has been known for decades, the study of mononuclear phagocytes in the context of kidney function and dysfunction is still at an early stage. The purpose of this review is to summarize the present knowledge regarding classification of these cells in the mouse kidney and to identify relevant questions that would further advance the field and potentially lead to new opportunities for treatment of acute kidney injury and other kidney diseases.

Wright-Giemsa staining to observe phagocytes in Locusta migratoria infected with Metarhizium acridum.

Hemocytes are the first line of defense in the invertebrate immune system. Understanding their roles in cellular immunity is important for developing more efficient mycoinsecticides. However, the exact classification of hemocytes has been inconsistent and the various types of phagocytes in Locusta migratoria are poorly defined. Herein, the Wright-Giemsa staining method and microscopy were employed to characterize the hemocytes of L. migratoria following infection by Metarhizium acridum. Hemocytes were classified into four types, including granulocytes, plasmatocytes, prohemocytes, and oenocytoids, based on size, morphology, and dye-staining properties. Each type of hemocyte was classified into several subtypes according to different ultrastructural features. At least four subtypes of granulocytes or plasmatocytes, including small-nucleus plasmatocytes, basophil vacuolated plasmatocytes, homogeneous plasmatocytes, and eosinophilic granulocytes, carried out phagocytosis. The percentage of total phagocytes increased two days after infection by M. acridum, then gradually declined during the next two days, and then increased sharply again at the fifth day. Our data suggested that plasmatocytes and granulocytes may be the major phagocytes that protect against invasion by a fungal pathogen in L. migratoria. Total hemocytes in locusts significantly increased in the initial days after infection and decreased in the late period of infection compared to controls. In the hemocoel, hyphal bodies were recognized, enwrapped, and digested by the phagocytes. Then, the broken hyphal pieces were packaged as vesicles to be secreted from the cell. Moreover, locusts might have a sensitive and efficient cellular immune system that can regulate phagocyte differentiation and proliferation before fungi colonize the host hemolymph.

Peripheral blood mononuclear phagocytes from patients with chronic periodontitis are primed for osteoclast formation.

BACKGROUND: During inflammatory periodontal disease, peripheral blood mononuclear cells (PBMCs) are attracted to bone and differentiate into active bone-resorbing osteoclasts (OCs), thus providing evidence that the impact of chronic periodontitis (CP) on the activity of circulating mononuclear cells is of central importance. The authors test the hypothesis that peripheral blood mononuclear phagocytes (PBMPs) from patients with CP are activated and more susceptible to differentiation into OCs, which in turn would lead to more intense bone resorption. METHODS: In vitro cytokine production by both unstimulated and lipopolysaccharide-stimulated PBMCs from individuals with (n = 10) or without (n = 12) periodontitis was determined by cytokine array. OC differentiation from CD14(+) PBMCs was induced by receptor activator of nuclear factor-kappa B ligand (RANKL), either alone or in the presence of macrophage colony-stimulating factor (M-CSF). PBMC differentiation to OCs was confirmed by tartrate-resistant acid phosphatase staining; bone resorbing activity was assessed by using an osteologic plate assay (bone resorption pit formation). RESULTS: PBMCs from patients with CP produced tumor necrosis factor-α and higher amounts of interferon-γ, interleukin (IL)-1α, IL-1ß, IL-1rα, CXC motif chemokine 10, macrophage migration inhibitory factor, macrophage inflammatory protein (MIP)-1α, and MIP-1ß than the control cells. OC differentiation was induced by RANKL alone in PBMCs from patients with CP, but not in PBMCs from the healthy controls, which required the addition of M-CSF. In addition, PBMC-derived OCs from patients with CP showed significantly higher resorption activity than that observed in the healthy controls. Also, the circulating concentrations of M-CSF were significantly higher in patients with CP than in the control participants. CONCLUSIONS: These data indicate that in patients with CP, circulating PBMCs are primed for increased proinflammatory activity and that M-CSF plays a central role in this process by increasing OC formation and the consequent bone resorption activity.

Phagocyte dynamics in a highly regenerative urochordate: insights into development and host defense.

Phagocytosis is a cellular process by which particles and foreign bodies are engulfed and degraded by specialized cells. It is functionally involved in nutrient acquisition and represents a fundamental mechanism used to remove pathogens and cellular debris. In the marine invertebrate chordate Botryllus schlosseri, cell corpse engulfment by phagocytic cells is the recurrent mechanism of programmed cell clearance and a critical process for the successful execution of asexual regeneration and colony homeostasis. In the present study, we have utilized a naturally occurring process of vascular parabiosis coupled with intravascular microinjection of fluorescent bioparticles and liposomes as tools to investigate the dynamics of phagocyte behavior in real-time during cyclical body regeneration. Our findings indicate that B. schlosseri harbors two major populations of post-mitotic phagocytes, which display distinct phagocytic specificity and homing patterns: a static population that lines the circulatory system epithelia, and a mobile population that continuously recirculates throughout the colony and exhibits a characteristic homing pattern within mesenchymal niches called ventral islands (VI). We observed that a significant proportion of ventral island phagocytes (VIP) die and are engulfed by other VIP following takeover. Selective impairment of VIP activity curtailed zooid resorption and asexual development. Together, these findings strongly suggest that ventral islands are sites of phagocyte homing and turnover. As botryllid ascidians represent invertebrate chordates capable of whole body regeneration in a non-embryonic scenario, we discuss the pivotal role that phagocytosis plays in homeostasis, tissue renewal and host defense.

Endoneurial fibroblast-like cells.

Endoneurial fibroblast-like cells (EFLCs) have been described for more than 60 years, but the embryology, functions, and pathology of these cells are not well defined. Several hypotheses of their origin have been proposed. A previous study suggesting that they were of neural crest origin is supported by our data in humans. This lineage might account for EFLCs having multiple biologic functions and involvement in pathological processes. Here, we review what is known about the origin; functions in collagen synthesis, phagocytosis, inflammatory responses, and immune surveillance; and the pathological alterations of EFLCs based on the literature and on our personal observations.

NK cell-derived interferon-γ orchestrates cellular dynamics and the differentiation of monocytes into dendritic cells at the site of infection.

Dendritic cells (DCs), monocytes, and/or macrophages initiate host-protective immune responses to intracellular pathogens in part through interleukin-12 (IL-12) production, although the relative contribution of tissue resident versus recruited cells has been unclear. Here, we showed that after intraperitoneal infection with Toxoplasma gondii cysts, resident mononuclear phagocytes are replaced by circulating monocytes that differentiate in situ into inflammatory DCs (moDCs) and F4/80(+) macrophages. Importantly, NK cell-derived interferon-γ (IFN-γ) was required for both the loss of resident mononuclear phagocytes and the local differentiation of monocytes into macrophages and moDCs. This newly generated moDC population and not the resident DCs (or macrophages) served as the major source of IL-12 at the site of infection. Thus, NK cell-derived IFN-γ is important in both regulating inflammatory cell dynamics and in driving the local differentiation of monocytes into the cells required for initiating the immune response to an important intracellular pathogen.

Plenary perspective: the complexity of constitutive and inducible gene expression in mononuclear phagocytes.

Monocytes and macrophages differentiate from progenitor cells under the influence of colony-stimulating factors. Genome-scale data have enabled the identification of the set of genes that distinguishes macrophages from other cell types and the ways in which thousands of genes are regulated in response to pathogen challenge. Although there has been a focus on a small subset of lineage-enriched transcription factors, such as PU.1, more than one-half of the transcription factors in the genome can be expressed in macrophage lineage cells under some state of activation, and they interact in a complex network. The network architecture is conserved across species, but many of the target genes evolve rapidly and differ between mouse and human. The data and publication deluge related to macrophage biology require the development of new analytical tools and ways of presenting information in an accessible form.

Antigen-presenting cell marker expression and phagocytotic activity in periodontal ligament cells.

BACKGROUND: Periodontal ligament (PDL) cells are the main cellular constituents of the periodontium, maintain the integrity of the connective tissue, and impact pathology in periodontitis. The aim of this study was to analyze whether PDL cells recognize foreign particles and participate in the immune response to periodontal pathogens. METHODS: Expression of surface proteins characteristic of antigen-presenting cells (APCs) (major histocompatibility complex [MHC] class II, CD40, CD80, CD86) was analyzed in PDL cells after challenge with the cytokines interleukin (IL)-1ß, IL-17A, and interferon-gamma (IFN-γ) or with heat-killed Aggregatibacter actinomycetemcomitans using real-time PCR and flow cytometry. Confocal laser scanning microscopy, transmitted light microscopy, flow cytometry, and time-lapse microscopy were applied to analyze their phagocytotic capacity of collagen (carboxylate-modified microspheres), non-periodontal (Escherichia coli) and periodontal (Aggregatibacter actinomycetemcomitans) pathogens. Furthermore, it was examined whether cytokine activation of PDL cells affects the phagocytosis of collagen or bacteria. RESULTS: PDL cells upregulated MHC class II after cytokine stimulation on transcriptional level, whereas co-stimulatory molecules characteristic of professional APCs were not induced. Analyses on protein level revealed that MHC class II was not constitutively expressed in all PDL cell lines used. PDL cells phagocytosed both collagen and bacteria via acidic vesicles, suggesting the formation of phagosomes. Phagocytosis could be partially inhibited by inhibitors of phagocytosis, i.e., dynasore and wortmannin. Pre-incubation with cytokines did not further enhance the phagocytosis rate of collagen or bacteria. CONCLUSIONS: These results suggest that PDL cells do not only represent bystanders in periodontal infections, but display non-professional APC characteristics, suggesting possible participation in immune reactions of the oral cavity.

Mononuclear phagocyte heterogeneity in cancer: different subsets and activation states reaching out at the tumor site.

Mononuclear phagocytes are amongst the most versatile cells of the body, contributing to tissue genesis and homeostasis and safeguarding the balance between pro- and anti-inflammatory reactions. Accordingly, these cells are notoriously heterogeneous, functioning in distinct differentiation forms (monocytes, MDSC, macrophages, DC) and adopting different activation states in response to a changing microenvironment. Accumulating evidence exists that mononuclear phagocytes contribute to all phases of the cancer process. These cells orchestrate the inflammatory events during de novo carcinogenesis, participate in tumor immunosurveillance, and contribute to the progression of established tumors. At the tumor site, cells such as tumor-associated macrophages (TAM) are confronted with different tumor microenvironments, leading to TAM subsets with specialized functions. A better refinement of the molecular and functional heterogeneity of tumor-associated mononuclear phagocytes might pave the way for novel cancer therapies that directly target these tumor-supporting cells.

CX3CR1 defines functionally distinct intestinal mononuclear phagocyte subsets which maintain their respective functions during homeostatic and inflammatory conditions.

Intestinal mononuclear phagocytes (iMNP) are critically involved in mucosal immunity and tissue homeostasis. Two major non-overlapping populations of iMNP have been identified in mice. CD103(+) iMNP represent a migratory population capable of inducing tolerogenic responses, whereas CX3CR1(+) iMNP are resident cells with disease-promoting potential. CX3CR1(+) iMNP can further be subdivided based on differential expression of CX3CR1. Using CX3CR1(GFP/+) ×RAG2(-/-) mice, we demonstrate that CX3CR1(hi) and CX3CR1(lo) iMNP clearly differ with respect to their morphological and functional properties. Compared with CX3CR1(hi) iMNP, CX3CR1(lo) iMNP are polarised towards pro-inflammatory responses already under homeostatic conditions. During a CD4(+) T-cell-induced colitis, CX3CR1(lo) cells accumulate in the inflamed mucosa and upregulate the expression of pro-inflammatory cytokines and triggering receptor expressed on myeloid cells-1 (TREM-1). In contrast, CX3CR1(hi) iMNP retain their non-inflammatory profile even during intestinal inflammation. These findings identify two functionally distinct iMNP subsets based on differential expression of CX3CR1 and indicate an unanticipated stability of iMNP.

[The characteristic of the coelomic fluid and coelomic epithelium cell populations of starfish Asterias rubens L., capable to attach and spread on various substrates].

Cultivation is one of the methods modeling processes occurring in vivo. The success of cultivation, in particular, is defined by a substratum choice. We studied the ability of coelomocytes and coelomic epithelial cells to attach and spread to fibronectin, laminin, polylysine, and glass. Qualitative composition of heterogeneous populations of coelomocytes and epithelial cells was determined after staining the cells with rhodamine-phalloidin and DAPI, and changes in the composition of populations evaluated in response to injury. Seven relative classes of coelomocytes has been identified, three of which has been shown to participate in the formation of clot during primary repair of wounds. There was a change in the proportion of these cells, attached to specific ligands in response to the injury. In coelomic epithelium 8 relative classes of cells has been identified, two of which are likely to be candidates for the role of progenitor cells for coelomocytes--coelomocyte-like and small epithelial cells with high nuclear-cytoplasmic ratio. The enrichment with the small cells in population of attached coelomic epithelium cells has been revealed when seeding on laminin. Continued viability of epithelial cells has been shown when cultured on laminin during 2 months.

Cell type specificity and host genetic polymorphisms influence antibody-dependent enhancement of dengue virus infection.

Antibody-dependent enhancement (ADE) is implicated in severe, usually secondary, dengue virus (DV) infections. Preexisting heterotypic antibodies, via their Fc-gamma receptor (FcγR) interactions, may increase disease severity through enhanced target cell infection. Greater numbers of infected target cells may contribute to higher viremia and excess cytokine levels often observed in severe disease. Monocytes, macrophages, and immature and mature dendritic cells (DC) are considered major cellular targets of DV. Apheresis of multiple donors allowed isolation of autologous primary myeloid target cell types for head-to-head comparison of infection rates, viral output, and cytokine production under direct infection (without antibody) or ADE conditions (with antibody). All studied cell types except immature DC supported ADE. All cells undergoing ADE secreted proinflammatory cytokines (interleukin-6 [IL-6] and tumor necrosis factor alpha [TNF-α]) at enhancement titers, but distinct cell-type-specific patterns were observed for other relevant proteins (alpha/beta interferon [IFN-α/ß] and IL-10). Macrophages produced type I interferons (IFN-α/ß) that were modulated by ADE. Mature DC mainly secreted IFN-ß. Interestingly, only monocytes secreted IL-10, and only upon antibody-enhanced infection. While ADE infection rates were remarkably consistent in monocytes (10 to 15%) across donors, IL-10 protein levels varied according to previously described regulatory single nucleotide polymorphisms (SNPs) in the IL-10 promoter region. The homozygous GCC haplotype was associated with high-level IL-10 secretion, while the ACC and ATA haplotypes produced intermediate and low levels of IL-10, respectively. Our data suggest that ADE effects are cell type specific, are influenced by host genetics, and, depending on relative infection rates, may further contribute to the complexity of DV pathogenesis.

Macrophage polarization: tumor-associated macrophages as a paradigm for polarized M2 mononuclear phagocytes.

Mononuclear phagocytes are versatile cells that can express different functional programs in response to microenvironmental signals. Fully polarized M1 and M2 (or alternatively activated) macrophages are the extremes of a continuum of functional states. Macrophages that infiltrate tumor tissues are driven by tumor-derived and T cell-derived cytokines to acquire a polarized M2 phenotype. These functionally polarized cells, and similarly oriented or immature dendritic cells present in tumors, have a key role in subversion of adaptive immunity and in inflammatory circuits that promote tumor growth and progression.

SpC3, the complement homologue from the purple sea urchin, Strongylocentrotus purpuratus, is expressed in two subpopulations of the phagocytic coelomocytes.

The lower deuterostomes, including the echinoderms, possess an innate immune system that includes a subsystem with similarities to the vertebrate complement system. A homologue of the central component of this system, C3, has recently been identified in the purple sea urchin, Strongylocentrotus purpuratus, and is called SpC3. We determined previously that coelomocytes specifically express the SpC3 gene (Sp064); however, the sea urchin has at least four different types of coelomocytes: amoeboid phagocytes, red spherule cells, colorless spherule cells, and vibratile cells. To determine which of these subpopulations expresses Sp064 and produces SpC3, coelomocytes were separated by discontinuous gradient density centrifugation. Relatively homogenous fractions were obtained consisting of the four major cell types in addition to two types of amoeboid phagocytes with different densities and distinct morphologies. Analysis of proteins from separated cell subpopulations by Western blot and analysis of gene expression by RT-PCR revealed that phagocytes express the gene and contain the protein. Immunolocalization showed that SpC3+ phagocytes are present as subsets of both the low- and high-density subpopulations of phagocytes; however, the subcellular localization of SpC3 is different in these two subpopulations.

A life stage of particle-laden rat dendritic cells in vivo: their terminal division, active phagocytosis, and translocation from the liver to the draining lymph.

Initiation of an adoptive immune response against pathogenic organisms, such as bacteria and fungi, may involve phagocytic activity of dendritic cells (DC) or their immature precursors as a prelude to antigen processing and presentation. After intravenous injection of rats with particulate matter, particle-laden cells were detected in the peripheral hepatic lymph. Since it has been known there is a constant efflux of DC from nonlymphoid organs into the draining peripheral lymph, we examined whether these particle-laden cells belonged to the DC or macrophage lineage. The majority of particle-laden cells in lymph showed immature monocyte-like cytology, and the amount of ingested particles was small relative to typical macrophages. We identified these particle-laden cells as DC based on a number of established criteria: (a) they had a phenotype characteristic of rat DC, that is, major histocompatibility complex class Ihigh+ and IIhigh+, intercellular adhesion molecule 1+ and 80% positive with the rat DC-specific mAb OX62; (b) they showed strong stimulating capacity in primary allogeneic mixed leukocyte reaction; (c) in vitro, they had little phagocytic activity; and (d) the kinetics of translocation was similar to that of lymph DC in that they migrated to the thymus-dependent area of the regional nodes. Furthermore, bromodeoxyuridine feeding studies revealed that most of the particle-laden DC were recently produced by the terminal division of precursor cells, at least 45% of them being <5.5 d old. The particle-laden DC, defined as OX62+ latex-laden cells, were first found in the sinusoidal area of the liver, in the liver perfusate, and in spleen cell suspensions, suggesting that the site of particle capture was mainly in the blood marginating pool. It is concluded that the particle-laden cells in the hepatic lymph are recently produced immature DC that manifest a temporary phagocytic activity for intravascular particles during or after the terminal division and that the phagocytic activity is downregulated at a migratory stage when they translocate from the sinusoidal area to the hepatic lymph.

Malacoplaquia del tracto genital femenino / Malacoplakia of female genitale tract

La malacoplaquia es un proceso granulomatoso inflamatorio crónico, poco frecuente que en raras ocasiones afecta el tracto genital femenino. Esta enfermedad parece ser debida a un defecto adquirido en la función bactericida de los histiocitos, estando con frecuencia asociada a bacterias coliformes, particularmente a Escherichia coli. Presentamos el primer caso de malacoplaquia en el tracto genital femenino reportado en Venezuela