Expression Of Macrophage Mannose Receptor Research Articles

Endogenous IFN-γ facilitates Pneumocystis infection and downregulates carbohydrate receptors in CD4+ Tcell-depleted mice.

IFN-γ plays a critical role in host defense against intracellular pathogens. IFN-γ is produced in the bronchoalveolar lavage fluid of mice infected with Pneumocystis, but the role of IFN-γ in host defense against Pneumocystis remains controversial. It has been previously reported that although exogenous IFN-γ has beneficial effects on eradication of Pneumocystis, endogenous IFN-γ has a negative impact on innate immunity in immunocompromised hosts. Surprisingly, CD4+ T cell-depleted IFN-γ deficient (GKO) mice exhibit resistance to Pneumocystis. Alveolar macrophages (AM) from GKO mice exhibit higher expression of macrophage mannose receptor (MMR) and Dectin-1. Concomitantly, they exhibited greater ability to phagocytize Pneumocystis, and this activity was suppressed by inhibitors of these receptors. Incubation with IFN-γ resulted in a reduction in both the expression of these receptors on AM and their Pneumocystis-phagocytic activity. These results indicate that endogenous IFN-γ facilitates Pneumocystis to escape from host innate immunity by attenuating the phagocytic activity of AM via downregulation of MMR and Dectin-1.

Mannose receptor is an HIV restriction factor counteracted by Vpr in macrophages.

HIV-1 Vpr is necessary for maximal HIV infection and spread in macrophages. Evolutionary conservation of Vpr suggests an important yet poorly understood role for macrophages in HIV pathogenesis. Vpr counteracts a previously unknown macrophage-specific restriction factor that targets and reduces the expression of HIV Env. Here, we report that the macrophage mannose receptor (MR), is a restriction factor targeting Env in primary human monocyte-derived macrophages. Vpr acts synergistically with HIV Nef to target distinct stages of the MR biosynthetic pathway and dramatically reduce MR expression. Silencing MR or deleting mannose residues on Env rescues Env expression in HIV-1-infected macrophages lacking Vpr. However, we also show that disrupting interactions between Env and MR reduces initial infection of macrophages by cell-free virus. Together these results reveal a Vpr-Nef-Env axis that hijacks a host mannose-MR response system to facilitate infection while evading MR's normal role, which is to trap and destroy mannose-expressing pathogens.

Stromal-targeting radioimmunotherapy mitigates the progression of therapy-resistant tumors

Radioimmunotherapy (RIT) aims to deliver a high radiation dose to cancer cells, while minimizing the exposure of normal cells. Typically, monoclonal antibodies are used to target the radionuclides to cancer cell surface antigens. However, antibodies face limitations due to their poor tumor penetration and suboptimal pharmacokinetics, while the expression of their target on the cancer cell surface may be gradually lost. In addition, most antigens are expressed in a limited number of tumor types. To circumvent these problems, we developed a Nanobody (Nb)-based RIT against a prominent stromal cell (stromal-targeting radioimmunotherapy or STRIT) present in nearly all tumors, the tumor-associated macrophage (TAM). Macrophage Mannose Receptor (MMR) functions as a stable molecular target on TAM residing in hypoxic areas, further allowing the delivery of a high radiation dose to the more radioresistant hypoxic tumor regions. Since MMR expression is not restricted to TAM, we first optimized a strategy to block extra-tumoral MMR to prevent therapy-induced toxicity. A 100-fold molar excess of unlabeled bivalent Nb largely blocks extra-tumoral binding of 177Lu-labeled anti-MMR Nb and prevents toxicity, while still allowing the intra-tumoral binding of the monovalent Nb. Interestingly, three doses of 177Lu-labeled anti-MMR Nb resulted in a significantly retarded tumor growth, thereby outcompeting the effects of anti-PD1, anti-VEGFR2, doxorubicin and paclitaxel in the TS/A mammary carcinoma model. Together, these data propose anti-MMR STRIT as a valid new approach for cancer treatment.

Evaluation of [99mTc]Radiolabeled Macrophage Mannose Receptor-Specific Nanobodies for Targeting of Atherosclerotic Lesions in Mice.

Macrophage accumulation characterizes the development of atherosclerotic plaques, and the presence of certain macrophage subsets might be an indicator of plaque phenotype and (in)stability. The macrophage mannose receptor (MMR) is expressed on alternatively activated macrophages and found at sites of intraplaque hemorrhage and neovascularization. It has been proposed as target to identify vulnerable plaques. Therefore, we aimed to assess the feasibility of using anti-MMR nanobodies (Nbs) as molecular tracers for nuclear imaging in an animal model of atherosclerosis. Anti-MMR and control Nb, radiolabeled with Tc-99m, were injected in ApoE-/- and/or C57Bl/6 mice (n=6). In vivo competition studies involving pre-injection of excess of unlabeled anti-MMR Nb (n=3) and injection of anti-MMR Nb in MMR-/- mice (n=3) were performed to demonstrate specificity. At 3 h p.i. radioactive uptake in organs, tissues and aorta segments were evaluated. Autoradiography and immunofluorescence were performed on aortic sections. Significantly higher uptake was observed in all aortic segments of ApoE-/- mice injected with anti-MMR Nb compared to control Nb (1.36±0.67 vs 0.38±0.13 percent of injected dose per gram (%ID/g), p≤0.001). Surprisingly, high aortic uptake was also observed in C57Bl/6 mice (1.50±0.43%ID/g, p≥0.05 compared to ApoE-/-), while aortic uptake was reduced to background levels in the case of competition and in MMR-/- mice (0.46±0.10 and 0.22±0.06%ID/g, respectively; p≤0.001). Therefore, expression of MMR along healthy aortas was suggested. Autoradiography showed no specific radioactive signal within atherosclerotic plaques, but rather localization of the signal along the aorta, correlating with MMR expression in perivascular tissue as demonstrated by immunofluorescence. No significant uptake of MMR-specific Nb could be observed in atherosclerotic lesions of ApoE-/- mice in this study. A specific perivascular signal causing a non-negligible background level was demonstrated. This observation should be considered when using MMR as a target in molecular imaging of atherosclerosis, as well as use of translational animal models with vulnerable plaques.

Effect of yeast-derived products and distillers dried grains with solubles (DDGS) on growth performance and local innate immune response of broiler chickens challenged with Clostridium perfringens

ABSTRACTThis study evaluated the effect of yeast-derived products on growth performance, gut lesion score, intestinal population of Clostridium perfringens, and local innate immunity of broiler chickens challenged with C. perfringens. One-day-old broiler chickens were randomly assigned to eight dietary treatments providing six replicate pens of 55 birds each per treatment. Dietary treatments consisted of Control diets without and with C. perfringens challenge, and diets containing bacitracin methylene disalicylate (BMD, 55 g/tonne), nucleotides (150 g/tonne), yeast cell wall (YCW, 300 g/tonne), and a commercial product Maxi-Gen Plus (1 kg/tonne) fed to chickens challenged with C. perfringens. Diets containing 10% distillers dried grains with solubles without and with C. perfringens challenge were also used. Birds were orally challenged with C. perfringens (108 colony-forming units (cfu)/bird) on day 14. On day 21, intestinal samples were collected for gene expression analysis. Pathogen challenge significantly (P < 0.05) impaired feed intake, body weight gain, and feed conversion ratio (FCR) shortly after the challenge (14–21 days). Increased C. perfringens counts and intestinal lesion scores were observed for challenged birds except the BMD-containing diet. Over the entire trial (1–35 days), no difference in growth performance was observed except the BMD diet which improved FCR over the Control, challenged group. Birds receiving nucleotides showed increased expression of toll-like receptors and cytokines interleukin (IL)-4 and IL-18 compared to the Control, challenged group. Expression of macrophage mannose receptor and IL-18 was upregulated in birds receiving YCW. Increased expression of cytokines and receptors involved in innate immunity in broilers receiving nucleotides and YCW suggests the immunomodulatory properties of these products under pathogen challenge conditions.

Effect of yeast-derived products and distillers dried grains with solubles (DDGS) on growth performance, gut morphology, and gene expression of pattern recognition receptors and cytokines in broiler chickens

An experiment was carried out to investigate the effect of yeast-derived products and distillers' dried grains with solubles (DDGS) on growth performance, small intestinal morphology, and innate immune response in broiler chickens from 1 to 21 d of age. Nine replicates of 5 birds each were assigned to dietary treatments consisting of a control diet without antibiotic (C), and diets containing 11 mg/kg of virginiamycin, 0.25% of yeast cell wall (YCW), 0.2% of a commercial product Maxi-Gen Plus, 0.025% of nucleotides, 0.05% of nucleotides, or a diet containing 10% of DDGS. On d 21, 5 birds per treatment were euthanized and approximately 5-cm long duodenum, jejunum, and ileum segments were collected for intestinal morphology measurements. Cecal tonsils and spleen were collected to measure the gene expression of toll-like receptors TLR2b, TLR4, and TLR21, macrophage mannose receptor (MMR), and cytokines IFN-γ, IL-12, IL-10, and IL-4. No significant difference was observed for growth performance parameters. However, diets containing 0.05% of nucleotides and YCW significantly increased (P < 0.05) villus height in the jejunum. Furthermore, the number of the goblet cells per unit area in the ileum was increased (P < 0.05) in diets supplemented with yeast-derived products. The expression of TLR2b in the spleen was down-regulated for diets supplemented with nucleotides and antibiotic. In addition, lower expression of TLR21 and MMR was observed in the spleen of birds receiving yeast-derived products and antibiotic. However, expression of TLR4 in the spleen was up-regulated in diets supplemented with YCW and nucleotides. The expression of IFN-γ and IL-12 was down-regulated in the spleen of birds fed diets supplemented with yeast-derived products. In addition, inclusion of YCW, Maxi-Gen Plus, or 0.05% of nucleotides down-regulated the expression of IL-10 and IL-4 in the cecal tonsils. In conclusion, down-regulation of receptors and cytokines in spleen and cecal tonsils of birds fed diets supplemented with yeast-derived products may suggest that yeast products do not exert immune stimulating effect under normal health conditions.

Enhanced resolution of experimental ARDS through IL-4-mediated lung macrophage reprogramming.

Despite intense investigation, acute respiratory distress syndrome (ARDS) remains an enormous clinical problem for which no specific therapies currently exist. In this study, we used intratracheal lipopolysaccharide or Pseudomonas bacteria administration to model experimental acute lung injury (ALI) and to further understand mediators of the resolution phase of ARDS. Recent work demonstrates macrophages transition from a predominant proinflammatory M1 phenotype during acute inflammation to an anti-inflammatory M2 phenotype with ALI resolution. We tested the hypothesis that IL-4, a potent inducer of M2-specific protein expression, would accelerate ALI resolution and lung repair through reprogramming of endogenous inflammatory macrophages. In fact, IL-4 treatment was found to offer dramatic benefits following delayed administration to mice subjected to experimental ALI, including increased survival, accelerated resolution of lung injury, and improved lung function. Expression of the M2 proteins Arg1, FIZZ1, and Ym1 was increased in lung tissues following IL-4 treatment, and among macrophages, FIZZ1 was most prominently upregulated in the interstitial subpopulation. A similar trend was observed for the expression of macrophage mannose receptor (MMR) and Dectin-1 on the surface of alveolar macrophages following IL-4 administration. Macrophage depletion or STAT6 deficiency abrogated the therapeutic effect of IL-4. Collectively, these data demonstrate that IL-4-mediated therapeutic macrophage reprogramming can accelerate resolution and lung repair despite delayed use following experimental ALI. IL-4 or other therapies that target late-phase, proresolution pathways may hold promise for the treatment of human ARDS.

ID: 92: Regulation of macrophage susceptibility to anti-CSF-1R antibody Emactuzumab treatment

Tumor-associated macrophages have been associated with disease progression and poor prognosis in various tumor types. Previously, patients with advanced metastatic disease have been treated with Emactuzumab, an antibody targeting the colony stimulating factor-1 cytokine receptor. Although treatment resulted in a strong reduction of tumor-associated macrophages in the vast majority of patients, the individual degree of tumor-associated macrophage depletion varied significantly. Hence we sought to identify factors that influence Emactuzumab-mediated killing. For this purpose, we used primary monocyte-derived human macrophages as a model system, and systematically investigated the impact of hypoxia, the macrophage polarizing TH2 secreted cytokine Interleukin (IL)-4 and macrophage-derived IL-10 on Emactuzumab-mediated killing. While hypoxia dramatically increased Emactuzumab-induced killing of macrophages under serum-free conditions, the presence of IL-4 but not IL-10 rescued macrophage viability. Notably, recombinant IL-4 treatment was associated with increased expression of macrophage mannose receptor 1 (CD206). This enhanced susceptibility of IL-10 polarized macrophages in a hypoxic environment was characterized by high expression of the Hemoglobin scavenger receptor scavenger receptor (CD163) and CSF-1R. Our findings suggest that Emactuzumab selectively reduces viability of CSF-1Rhi CD163hi while sparing CSF-1Rlo CD206hi macrophages in vitro. These results may help to identify patient subgroups expected to show less substantial depletion of tumor-associated macrophage after Emactuzumab treatment and may decipher if a correlation between the magnitude of tumor-associated macrophage depletion and clinical benefit exists.

SAT0075 The use of macrophage mannose receptor-targeting nanobodies and spect imaging to study joint inflammation in mice with collagen-induced arthritis

BackgroundRheumatoid arthritis (RA) is a chronic autoimmune disease that occurs in 0.5-1.0% of the population worldwide. The primary affected organ is the small diarthrodial joint, where the synovial membrane, cartilage...

Astragalus polysaccharide induces anti-inflammatory effects dependent on AMPK activity in palmitate-treated RAW264.7 cells

Astragalus polysaccharide (APS) has been reported to increase insulin sensitization and to ameliorate diabetes in animal models, and studies have demonstrated that this effect may be correlated with its anti-inflammatory roles invivo and invitro. However, the potential pharmacological mechanisms of APS in anti-inflammatory regulation are still poorly understood. Herein, RAW264.7 cells treated with APS showed anti-inflammatory effects. Interleukin (IL)-10 protein levels and expression of most of the anti-inflammatory genes, including IL-10, macrophage mannose receptor (MMR), arginase, Dectin-1, YM-1 and YM-2, were significantly increased after treatment with APS for 24h. Furthermore, to determine whether APS plays a potential role in RAW264.7 cell inflammation, we pretreated RAW264.7 cells with APS in the presence of palmitate. The results showed that APS markedly recovered the impairment of AMPK activity induced by palmitate. Furthermore, APS induced IL-10 protein production and anti-inflammatory gene expression of IL-10, MMR, Dectin-1, arginase, YM-1 and YM-2. Additionally, APS inhibited IL-1β protein production and expression of most of the pro-inflammatory genes, such as IL-1β, iNOS, MCP-1, IL-6 and CD11c but not tumor necrosis factor (TNF)-α. Notably, the effect of APS on inflammatory genes, except for TNF-α, was abrogated when AMPK activity was inhibited using a DN-AMPK plasmid. These results suggest that APS effectively ameliorates palmitate-induced pro-inflammatory responses through AMPK activity.

SPECT Imaging of Joint Inflammation with Nanobodies Targeting the Macrophage Mannose Receptor in a Mouse Model for Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease occurring in approximately 1% of the worldwide population. The disease primarily affects the joints, where inflammatory cells, such as macrophages, invade the synovium and cause cartilage and bone destruction. Currently, it is difficult to efficiently diagnose and monitor early-stage RA. In this study, we investigated whether SPECT/micro-CT imaging with (99m)Tc-labeled Nanobodies directed against the macrophage mannose receptor (MMR) is a useful tool for monitoring and quantifying joint inflammation in collagen-induced arthritis (CIA), a mouse model for RA. The expression of MMR was analyzed on macrophages and osteoclasts generated in vitro and in cells obtained from various organs from mice with CIA. CIA was induced in DBA/1 mice by injection of collagen type II in complete Freund adjuvant, and cell suspensions from the inflamed joints and other organs were obtained. Macrophages and osteoclasts were generated in vitro from bone marrow cells. Expression of MMR was quantified by quantitative polymerase chain reaction and flow cytometry with specific Nanobodies and conventional antibodies. SPECT/micro-CT imaging was performed with (99m)Tc-labeled MMR and control Nanobodies. MMR was highly expressed on macrophages and to a lesser extent on osteoclasts generated in vitro. In mice with CIA, MMR expression was detected on cells from the bone marrow, lymph nodes, and spleen. In synovial fluid of arthritic joints, MMR was expressed on CD11b(+)F4/80(+) macrophages. On in vivo SPECT/micro-CT imaging with consecutive injections of MMR and control Nanobodies, a strong MMR signal was seen in the knees, ankles, and toes of arthritic mice. Quantification of the SPECT imaging confirmed the specificity of the MMR signal in inflamed joints as compared with the control Nanobody. Dissection of the paws revealed an additional significant MMR signal in nonarthritic paws of affected mice (i.e., mice displaying symptoms of arthritis in other paws). Our data show that MMR is expressed on macrophages in vitro and in vivo in synovial fluid of inflamed paws, whereas expression is relatively low in other tissues. The use of Nanobodies against MMR in SPECT/micro-CT imaging generates the possibility to track inflammatory cells in vivo in arthritic joints.

Low‐dose azithromycin improves phagocytosis of bacteria by both alveolar and monocyte‐derived macrophagesin chronic obstructive pulmonary disease subjects

Chronic inflammation and reduced airways integrity in chronic obstructive pulmonary disease (COPD) potentially results from secondary necrosis as a result of impaired phagocytosis of apoptotic material by airway macrophages, and increased bacterial colonization. We have previously shown that administration of low-dose azithromycin to subjects with COPD improved macrophage phagocytosis of apoptotic airway epithelial cells, reduced inflammation and increased expression of macrophage mannose receptor. We firstly investigated whether there were defects in the ability of both alveolar (AM) and monocyte-derived macrophages (MDM) to phagocytose bacteria in COPD, as we have previously reported for phagocytosis of apoptotic cells. We then assessed the effects of administration of low-dose azithromycin to COPD patients on the ability of AM and MDM to phagocytose bacteria. Azithromycin (250 mg orally daily for 5 days then 2× weekly (total 12 weeks)) was administered to 11 COPD subjects and phagocytosis of fluorescein isothiocyanate-labelled Escherichia coli assessed by flow cytometry. COPD subjects had a significant defect in the ability of both AM and MDM to phagocytose bacteria that was significantly improved by administration of low-dose azithromycin The data provide further support for the long-term use of low dose azithromycin as an attractive adjunct treatment option for COPD. Improved clearance of both apoptotic cells and bacteria in the airway may have a dual effect; reducing the risk of secondary necrosis and release of toxic cell contents that perpetuate inflammation as well as contributing to a reduction in the rate of exacerbations in COPD.

The immunomodulatory glycan LNFPIII initiates alternative activation of murine macrophages in vivo

The early pathogen-macrophage interactions that help drive macrophage maturation towards classically or alternatively activated are largely unknown. To examine this question we utilized the immunomodulatory glycan Lacto-N-fucopentaose III (LNFPIII), which contains the Lewis X (LeX) trisaccharide, to activate murine peritoneal macrophages in vivo. Because LNFPIII is known to induce anti-inflammatory responses, we asked if LNFPIII stimulation of macrophages in vivo initiates alternative activation events such as upregulation of Arginase 1, Ym1, FIZZ-1, MGL-1 or macrophage mannose receptor (MMR). Examination of peritoneal exudate cells from mice 20 hr post-LNFPIII injection demonstrated increased Arginase 1 activity, at the mRNA and protein levels, coincident with undetectable inducible nitric oxide synthase expression or nitric oxide production. In addition to Arginase 1, Ym1 expression was also significantly upregulated at 20 and 48 hr after LNFPIII exposure in vivo. However, the expression of FIZZ-1, MGL-1, and MMR was not changed in these macrophages. In an attempt to determine activation requirements for functional activity, we adoptively transferred antigen-pulsed, in vivo LNFPIII activated macrophages into naïve recipients and found that they were capable of triggering recipient T cells to secrete elevated levels of interleukin (IL)-10 and IL-13 compared to mice receiving control macrophages. Together, these data demonstrate that upregulation of expression of Arginase 1 and Ym1 occur very early in activation of macrophages, and can be independent of other alternatively activated (AA) macrophage markers. Importantly, these early events appear to be IL-4/IL-13-independent in our model. In the future we hope to determine if upregulation of these initial AA maturational events is sufficient for these macrophages to exert immunoregulatory activity in vivo.

Characterisation and trophic functions of murine embryonic macrophages based upon the use of a Csf1r–EGFP transgene reporter

All solid organs contain resident monocyte-derived cells that appear early in organogenesis and persist throughout life. These cells are critical for normal development in some organs. Here we report the use of a previously described transgenic line, with EGFP driven by the macrophage-restricted Csf1r ( c-fms) promoter, to image macrophage production and infiltration accompanying organogenesis in many tissues. Using microarray analysis of FACS-isolated EGFP-positive cells, we show that fetal kidney, lung and brain macrophages show similar gene expression profiles irrespective of their tissue of origin. EGFP-positive cells appeared in the renal interstitium from 12 days post coitum, prior to nephrogenesis, and maintain a close apposition to renal tubules postnatally. CSF-1 added to embryonic kidney explants increased overall renal growth and ureteric bud branching. Expression profiling of tissue macrophages and of CSF-1-treated explants showed evidence of the alternate, pro-proliferative (M2) activation profile, including expression of macrophage mannose receptor (CD206), macrophage scavenger receptor 2 (Msr2), C1q, CD163, selenoprotein P, CCL24 and TREM2. This response has been associated with the trophic role of tumour-associated macrophages. These findings suggest a trophic role of macrophages in embryonic kidney development, which may continue to play a similar role in postnatal repair.

Noninfectious entry of HIV-1 into peripheral and brain macrophages mediated by the mannose receptor.

Although protein receptors on the plasma membrane involved in the initial steps of productive HIV-1 infection have been well characterized, little is known about interactions between cellular carbohydrate receptors and HIV-1. Here, we report the involvement of a carbohydrate receptor, the macrophage mannose receptor (MR), and its role in supporting HIV-1 binding and entry. HIV-1 can enter the cytoplasm of human macrophages and microglia as well as murine macrophages by MR, although no subsequent viral replication was observed. Correspondingly, HIV-1 entry into Cos-7 cells after induction of expression of MR by transfection with MR-cDNA did not demonstrate viral replication. Our studies suggest that whereas MR may serve as a binding and an entry site, the MR-mediated pathway does not lead to productive HIV-1 infection. In addition, we report that recombinant HIV-1 gp120 blocks MR-mediated phagocytosis in human and murine alveolar macrophages and microglial cells. Therefore, characterization of the HIV-1 noninfectious MR-mediated phagocytic pathway may foster advances in HIV-1 vaccine design and an improved understanding of HIV-1/AIDS pathogenesis and host defenses.

Differential infection of mononuclear phagocytes by Francisella tularensis: role of the macrophage mannose receptor

Francisella tularensis (Ft) is a Gram-negative bacterium and the causative agent of tularemia. It is well established that this organism replicates inside macrophages, but we are only beginning to understand this interface at the molecular level. Herein, we compared directly the ability of Ft subspecies holarctica live-vaccine strain to infect freshly isolated human peripheral blood monocytes, monocyte-derived macrophages (MDM), and cells of the murine macrophage cell line J774A.1 (J774). We now show that unopsonized bacteria infected human MDM fivefold more efficiently than monocytes or J774 cells in standard media. Moreover, enhanced infection of MDM was mediated, in part, by the macrophage mannose receptor (MR). Forming Ft phagosomes accumulated MR, and infection was inhibited by MR-blocking antibody or soluble mannan but not by the dectin-1 ligand laminarin. Up-regulation of MR in MDM (by exposure to interleukin-4) increased Ft phagocytosis, as did expression of MR in J774 cells. Conversely, opsonized Ft were ingested readily by monocytes and MDM. Medium supplementation with 2.5% fresh autologous serum was sufficient to confer opsonophagocytosis and CD11b accumulated in the membrane at sites of Ft engulfment. Infection of monocytes by opsonized Ft was nearly ablated by complement receptor 3 (CR3) blockade. Conversely, MDM used MR and CD11b/CD18 to ingest opsonized organisms. Altogether, our data demonstrate differential infection of mononuclear phagocytes by Ft and define distinct roles for MR and CR3 in phagocytosis.

The involvement of the macrophage mannose receptor in the innate immune response to infection with parasite Trichinella spiralis

The macrophage mannose receptor (MR) is a pattern recognition receptor of the innate immune system that binds to microbial structures bearing mannose, fucose and N-acetylglucosamine on their surface. The MR can mediate endocytosis and phagocytosis, as well as activation of macrophages and antigen presentation. Since Trichinella spiralis antigens are rich in oligomannose residues, we investigated whether a mannose-recognizing receptor, such as the MR, participated in the host–parasite interaction. The results show that the MR (either on the surface of macrophages or in the purified form) recognizes and binds components of T. spiralis muscle larvae. The presence of parasites provoked activation of peritoneal macrophages, which was indicated by down-regulation of MR expression, and the stimulation of NO secretion. In vitro stimulation of macrophages with T. spiralis components resulted in increased NO and IL-6 production. However, while the MR was partially involved in stimulation of NO production, it did not mediate IL-6 secretion.

Pulmonary Surfactant Protein A Activates a Phosphatidylinositol 3-Kinase/Calcium Signal Transduction Pathway in Human Macrophages: Participation in the Up-Regulation of Mannose Receptor Activity

Surfactant protein A (SP-A), a major component of lung surfactant, binds to macrophages and has been shown to alter several macrophage biological functions, including up-regulation of macrophage mannose receptor (MR) activity. In the present study, we show that SP-A induces signal transduction pathway(s) that impact on MR expression. The addition of human, rat, or recombinant rat SP-A to human monocyte-derived macrophages significantly raised the level of cytosolic Ca2+ above baseline within 10 s of SP-A addition, as measured by spectrofluorometric analysis. SP-A induced a refractory state specific for SP-A consistent with homologous desensitization of a receptor(s) linked to calcium mobilization because a second application of SP-A did not induce a rise in cytosolic Ca2+ whereas the addition of platelet-activating factor did. Using site-directed mutations in SP-A, we determined that both the attached sugars and the collagen-like domain of SP-A are necessary to optimize Ca2+ mobilization. SP-A triggered the increase in cytosolic Ca2+ by inducing activation of phospholipase C, which leads to the hydrolysis of membrane phospholipids, yielding inositol 1,4,5-trisphosphate and mobilizing intracellularly stored Ca2+ by inositol triphosphate-sensitive channels. Finally, inhibition of PI3Ks, which appear to act upstream of phospholipase C in Ca2+ mobilization, decreased the SP-A-induced rise in MR expression, providing evidence that SP-A induction of MR activity involves the activation of a pathway in which PI3K is a component. These studies provide further evidence that SP-A produced in the lung plays a role in modulating macrophage biology, thereby contributing to the alternative activation state of the alveolar macrophage.

Macrophage mannose receptor in chronic sinus disease.

The role of infectious agents in the onset and maintenance of chronic sinus disease is still not fully understood. Macrophage mannose receptor (MMR), an innate pattern recognizing receptor, capable of phagocytosis of invaders and signal transduction for proinflammatory mechanisms, might be of importance in immune interactions in chronic sinus disease. We examined the MMR in sinonasal airway mucosa to evaluate its possible role in chronic rhinosinusitis (CS) and nasal polyposis (NPs). Surgical samples from patients with sinonasal disease were investigated with real-time RT-PCR for quantification of MMR mRNA expression, and the presence and location of MMR-positive cells was analysed by immunohistochemistry. Quantification of MMR mRNA showed a statistically significant higher expression in NPs compared to CS without NP and controls. Immunohistochemistry revealed expression of MMR in all tissue samples; however, in NP we found an enhanced positive cellular staining including cell aggregates. We could demonstrate for the first time that the expression of MMR is significantly upregulated in NP compared to patients with CS without NP or turbinate tissue of controls. Macrophages expressing MMR, accumulated in cell aggregates in NPs, play a possible key role in pathogen-macrophage interaction in NP disease.

The macrophage mannose receptor (MMR) and toll-like receptor 2 (TLR2) and 4 (TLR 4) in chronic sinus disease

Rationale Innate pattern recognizing receptors (MMR, TLR 2 and TLR4), capable of recognizing pathogen recognizing molecular patterns and signal transduction for proinflammatory mechanisms, might have an important role in immune interactions in chronic sinus disease. Methods Surgical samples from patients with chronic rhinosinusitis (CS, n=10), nasal polyps (NPs, n=10) and controls (turbinate tissue, n=10) were investigated with real time RT-PCR for MMR, TLR 2 and TLR4 mRNA expression and the presence and location of MMR positive cells was analyzed by immunohistochemistry. Results Quantification of MMR mRNA showed a statistically significant higher expression in NPs compared to CS (p=0.04) and controls (p=0.001). Although immunohistochemistry revealed expression of MMR in all tissue samples, only in NP we found an enhanced positive cellular staining including cell aggregates. Quantification of TLR 2 and TLR 4 mRNA showed no difference of expression in CS compared to NP. Yet, TLR-2 and TLR-4 mRNA expression in nasal tissues were significantly correlated (r=0.57, p=0.001) and was found in all tissue samples. Conclusions We demonstrated for the first time that the expression of MMR is significantly up-regulated in NP compared to patients with CS or turbinate tissue of controls. Macrophages expressing MMR, accumulated in cell aggregates in NP, play a possible key role in pathogen-macrophage interaction in NP disease. Toll-like receptor expression in all sino-nasal tissue illustrates their possibly important immunological sentinel function in upper airway mucosa.