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Keywords:

  • Human;
  • Monocytes/macrophages;
  • Fungal;
  • Cell surface molecules;
  • Inflammation

Abstract

  1. Top of page
  2. Abstract
  3. Introduction
  4. Results and discussion
  5. Materials and methods
  6. Acknowledgements

We identified the C-type-lectin-like receptor, Dectin-1, as the major receptor for fungal β-glucans on murine macrophages and have demonstrated that it plays a significant role in the cellular response to these carbohydrates. Using two novel, isoform-specific mAb, we show here that human Dectin-1, the β-glucan receptor (βGR), is widely expressed and present on all monocyte populations as well as macrophages, DC, neutrophils and eosinophils. This receptor is also expressed on B cells and a subpopulation of T cells, demonstrating that human Dectin-1 is not myeloid restricted. Both major functional βGR isoforms – βGR-A and βGR-B – were expressed by these cell populations in peripheral blood; however, only βGR-B was significantly expressed on mature monocyte-derived macrophages and immature DC, suggesting cell-specific control of isoform expression. Inflammatory cells, recruited in vivo using a new skin-window technique, demonstrated that Dectin-1 expression was not significantly modulated on macrophages during inflammation, but is decreased on recruited granulocytes. Despite previous reports detailing the involvement of other β-glucan receptors on mature human macrophages, we have demonstrated that Dectin-1 acted as the major β-glucan receptor on these cells and contributed to the inflammatory response to these carbohydrates.

Abbreviations:
βGR:

β-Glucan receptor

FSC:

Forward scatter

GluP:

Glucan phosphate

SSC:

Side scatter

Introduction

  1. Top of page
  2. Abstract
  3. Introduction
  4. Results and discussion
  5. Materials and methods
  6. Acknowledgements

The innate recognition of microbes is an essential first step for the development of appropriate immune responses. This recognition is mediated by germ-line encoded receptors, including the so-called pattern-recognition receptors (PRR), which recognize structurally conserved microbial components 1. Many PRR have been identified, including the TLR, which play a central role in initiating intracellular signaling cascades in response to pathogens 2. The involvement of other non-TLR receptors in the modulation of these intracellular signals has only recently become appreciated 3, 4. Although many of the receptors and mechanisms involved in the detection of bacteria have been identified, less is known about the recognition of fungi. One key component appears to be the detection of fungal cell-wall carbohydrates 5. In particular, β-glucans are major structural components in many fungi and the ability of the mammalian immune system to recognize and respond to these carbohydrates has been known for several decades. In addition, β-glucans have been used experimentally and therapeutically as immunomodulators, potentiating host responses towards tumors and a variety of infections 5.

In the mouse, Dectin-1 was identified as the major receptor for β-glucans on macrophages and shown to mediate the proinflammatory response to these carbohydrates, and intact yeast, in collaboration with the TLR 4, 68. Dectin-1 is a type-II transmembrane receptor that possesses an extracellular carbohydrate-recognition domain, a stalk and transmembrane region and an intracellular cytoplasmic tail that contains an ITAM-like motif 9. The human homologue of Dectin-1, termed the β-glucan receptor (βGR), differs from the murine receptor in that it is alternatively spliced into two major and a number of minor isoforms 1013. The two major isoforms – βGR-A and βGR-B – which differ by the presence and absence of a stalk region, respectively, have both been shown to be functional for β-glucan recognition 10. In addition to recognizing β-glucans, Dectin-1 also recognizes an unidentified endogenous ligand on T cells, acting as a co-stimulatory molecule and inducing the proliferation of both CD4+ and CD8+ T cells in vitro9, 10, 13.

On primary human cells, however, a number of other receptors have been proposed to recognize β-glucans, including CR3 14, scavenger receptors 15 and lactosylceramide 16. Given the importance of β-glucan recognition in immunity and the major role of Dectin-1 in this process in murine macrophages, we undertook to characterize the cellular distribution and function of this receptor on human leukocytes. Using two novel mAb, we show here that the βGR is widely expressed and that it acts as the major receptor for β-glucans on primary human macrophages and contributes to the proinflammatory response to these carbohydrates.

Results and discussion

  1. Top of page
  2. Abstract
  3. Introduction
  4. Results and discussion
  5. Materials and methods
  6. Acknowledgements

Generation of novel anti-human-βGR mAb

To explore the role of the human Dectin-1 (βGR) on primary cells, we generated novel mAb from C57BL/6 mice immunized with NIH3T3 cells expressing the full-length βGR isoform, βGR-A, as described in the “Materials and methods” section. Two mAb were identified, GE2 (IgG1), which recognizes both of the functional βGR isoforms – βGR-A and βGR-B – and BD6 (IgG2b), which recognizes βGR-A only (Fig. 1A). The specificity of these antibodies was demonstrated by specific staining of the respective βGR isoforms on the surface of live transfected cells, demonstrating that they recognized extracellular epitopes. Given their specificities, and the structure of the receptor, it is likely that GE2 recognizes the carbohydrate-recognition domain whereas BD6 recognizes either the stalk region or a membrane-proximal epitope on the CRD.

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Figure 1. Fig. 1. Characterization of novel anti-human-βGR antibodies. (A) Flow-cytometric analysis of NIH3T3 fibroblasts expressing βGR-A (solid histograms), βGR-B (dotted histograms) or untransfected control cells (grey histograms) stained with GE2 or BD6, as indicated. GE2 recognized both βGR-A and βGR-B, whereas BD6 recognized βGR-A only. (B) Inhibition of zymosan recognition by transfected NIH3T3 fibroblasts using GE2, BD6 or the soluble β-glucan (GluP), as indicated. GE2, but not an isotype-matched control or BD6, inhibits zymosan recognition to a level comparable with GluP, demonstrating that it can block human Dectin-1 function. Shown are mean ± SD of data pooled from at least three independent experiments.

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As we had previously been successful in using an inhibitory mAb to examine the expression and function of Dectin-1 in primary murine cells 6, 7, we assessed the ability of GE2 and BD6 to inhibit recognition of the β-glucan-rich particle, zymosan, by NIH3T3 cells expressing βGR-A or βGR-B (Fig. 1B). Cells expressing βGR-A or βGR-B were able to recognize zymosan and intact yeast, in a β-glucan-dependent fashion 10 and, as expected, zymosan binding by cells expressing these receptors was inhibited by the soluble β-glucan, glucan phosphate (GluP). Furthermore, GE2, but not an isotype control, was able to inhibit zymosan binding to a similar degree to that obtained by GluP, indicating that the mAb could inhibit receptor function. BD6 had no effect on zymosan binding. Thus we have generated isoform-specific mAb that can be used to define the expression and function of the human βGR in primary cells.

Distribution of the βGR in human peripheral blood cells

The activity of βGR has been described on a variety of human leukocytes including monocytes 17, macrophages 18, eosinophils 19, neutrophils 20 and NK cells 21, and we had previously detected βGR mRNA in some of these cell populations 10. To demonstrate the presence of this receptor on these cells, we examined surface expression of βGR on human PBL by flow cytometry, using GE2 to detect both major functional βGR isoforms. Although the levels of the βGR were relatively low, a number of cell populations expressing this receptor were detected, mostly consistent with the previous data described above (Fig. 2A). Cells were initially separated into three major populations – granulocytes (gate R1), monocytes (gate R2) and lymphocytes (gate R3) – based on size and granularity, and then further subdivided using cell-specific markers.

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Figure 2. Expression of βGR in peripheral blood, detected with GE2. (A) Flow-cytometric analysis of peripheral blood, after erythrocyte lysis and blocking, as detailed in the ”Materials and methods“ section, showing the identification and gating of the three major blood populations – granulocytes (R1), monocytes (R2) and lymphocytes (R3) – as well as whole-blood staining showing that all three populations contain βGR-expressing cells. (B) Demonstration of expression of βGR on both major granulocyte populations – eosinophils and neutrophils. Although βGR expression was always detected on eosinophils, the level of expression was donor variable. (C) Expression of βGR on defined monocyte populations, including recruited and inflammatory cells, and DC. (D) Expression of βGR was also detectable on B lymphocytes and CD4+ T lymphocytes. These data are representative of at least three independent donors. The gray histograms represent the isotype controls and the filled dark histograms represent GE2 staining, as indicated.

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In the granulocyte population, both neutrophils (CD15+CD16+) and eosinophils (CD15+CD16) expressed the βGR on their cell surface, although the level of expression on eosinophils was more variable (Fig. 2B). The presence of the βGR on eosinophils is of particular interest, as a number of studies have implicated these cells in allergic pulmonary disease following inhalation of β-glucans 22, 23. Indeed, β-glucans have been shown to induce activation of these cells in vitro19. However, Dectin-1 is not expressed on these cells in the mouse 24, which have similar pulmonary responses to these carbohydrates 25, suggesting that expression of this receptor on human eosinophils may not be linked with disease.

Receptors for β-glucan were initially defined on human monocytes as receptors for unopsonised zymosan 26, 27, and the presence of the βGR on these cells is consistent with these early findings (Fig. 2C). Monocytes have been divided into two main subsets, now termed the “recruited” (CD14lowCD16+) and “inflammatory” (CD14+CD16) cells 28, 29, both of which have been shown to recognize zymosan 30. We detected the βGR on the surface of both these cell types as well as on a third, intermediate population (CD14+CD16low), whose function is unclear. Expression of βGR was also detected on peripheral blood myeloid DC (CD1c+CD19), consistent with previous reports 13, but not on BDCA2+ plasmacytoid DC.

A fraction of the lymphocytes [R3: low forward scatter (FSC) and side scatter (SSC)] expressed the βGR, which upon further staining were identified as (CD19+) B cells and (CD3+CD4+) T cells (Fig. 2D). In some donors, a potentially activated CD3lowCD4low T cell population was observed that had higher levels of βGR surface expression (data not shown). The presence of βGR has not previously been defined on lymphocytes, although we had detected Dectin-1 mRNA expression in B and T cell lines 10, and there are some reports that their activities can be influenced by these carbohydrates 31, 32. In addition to the recognition of β-glucans, the βGR on these cells may also be involved in mediating interactions with other lymphocytes through recognition of the unidentified endogenous ligand 9, 10, 13.

It has been shown that β-glucans modulate NK cell function through a receptor distinct from CR3 21, 33. However, we did not detect the βGR on these cells (CD56+CD16+) (Fig. 2D), suggesting other receptor(s) were mediating these activities. Although βGR is classified as an NK-like C-type lectin, the lack of expression on NK cells is not surprising, given that Dectin-1 forms part of a subgroup of these receptors that is predominantly expressed on myeloid and other cells 34. All other lymphocyte populations, including NKT cells (CD56+CD3+) and CD8+ T cells, were essentially negative for βGR expression.

The human βGR is alternatively spliced into two major isoforms – βGR-A and βGR-B – which differ by the presence and absence of a stalk region, respectively 10. By Northern blotting, these two molecules appeared to be differentially expressed in granulocytes (expressing βGR-A and βGR-B) and monocytes/macrophages (expressing βGR-B only) 10. To explore this in more detail, we examined the distribution of βGR-A on peripheral blood cells using the mAb BD6 (Fig. 3A). Although BD6 staining was as efficient as GE2 on transfected cells (Fig. 1), it stained primary cells poorly. This may be due to low levels of this isoform on the cell surface, but as human Dectin-1 is thought to form complexes with at least one other receptor, CD63 35, the poor staining may also be due to steric hindrance of the epitope recognized by this mAb. Nevertheless, βGR-A was detected on the various cell populations that had been identified as GE2+ (Fig. 3B), although some donor variability in the levels of this receptor was observed on monocytes and CD4+ T cells (data not shown). Thus, differential expression of the βGR isoforms, particularly on monocytes, was not apparent on human peripheral blood cells.

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Figure 3. Expression of βGR-A detected with BD6 on peripheral blood cells. Although βGR-A could only be poorly detected with BD6 on the surface of live peripheral cells, as shown in the whole-blood staining (A), the presence of this isoform was detected on all populations gated as shown in Fig. 2A (B). The data are representative of at least three different donors, although some donor variability in receptor levels on monocytes and T lymphocytes was noted (data not shown). The gray histograms represent the isotype controls and the filled dark histograms represent BD6 staining.

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βGR expression during monocyte maturation

In tissues, monocytes are recruited from the blood and they differentiate into macrophages and DC. As we had demonstrated that Dectin-1 was highly expressed on inflammatory murine macrophages and some murine tissue macrophages, and DC 24, 36, we next examined the changes in human βGR expression during monocyte differentiation in vitro (Fig. 4). For this analysis, peripheral blood monocytes were cultured as described in the “Materials and methods” section, and examined for βGR expression at various time-points with other known surface markers, to monitor cellular differentiation. During monocyte differentiation into macrophages, characterized by the down-regulation of CD14 and the up-regulation of HLA-DR 37, 38, βGR expression tended to decrease, but remained detectable by day 7. The decrease in expression was not due to internalization of the receptor, as no intracellular pools of Dectin-1 were detected (data not shown). Expression of βGR-A, as detected by BD6, decreased during maturation into macrophages and was not detectable on any donor by day 7.

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Figure 4. Expression of βGR-A and βGR-B on monocyte-derived macrophages and DC. The expression of βGR, as detected by GE2, was observed to decrease during differentiation into macrophages but to increase during differentiation into immature DC. The expression of βGR-A, detected with BD6, was low/absent on both cell types. Maturation of DC with Salmonella LPS greatly reduced βGR expression. HLA-DR, CD14, DC-SIGN and CD86 were included as markers of macrophage and DC maturation, as described in the text. The gray histograms represent the isotype controls and the filled dark histograms represent specific antibody staining, as indicated. The data are representative of at least three different donors.

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The expression of the βGR was also examined with GE2 on monocytes cultured in GM-CSF and IL-4, to induce a DC-like phenotype 39 (Fig. 4). Elevated levels of the βGR were detected on the immature DC, which express DC-SIGN and reduced levels of CD14, at day 4 but maturation of these cells with LPS, characterized by the lack of CD14 and up-regulation of CD86 40, 41, resulted in down-regulation of the βGR. These changes in βGR expression may reflect similar regulatory mechanisms to Dectin-1 on murine macrophages, where has been shown to be up-regulated by IL-4 and GM-CSF and down-regulated by LPS 42. Little or no βGR-A was detected with BD6 on any DC population.

The lack of detectable expression of βGR-A on DC and mature macrophages indicates that this receptor does undergo cell-specific control of alternative splicing during monocyte maturation, as previously mentioned 10. This further suggests that the various isoforms may serve specific roles in each cell type. As βGR-A and βGR-B are equally functional for β-glucan recognition 10, there may be differences in their ability to interact with T cells. Indeed, the contact site between antigen-presenting cells and T cells (the immunological synapse) is known to require particular molecular spacing and redistribution of receptors 43, and the presence or absence of a stalk region, as found in the βGR isoforms, is perhaps suggestive of a role in this process.

βGR expression in an in vivo inflammatory model

We next examined the expression of the βGR in an inflammatory setting, using a skin-window model to study expression of this receptor on recruited myeloid cells ex vivo. In this model, cells recruited onto filter-paper discs, which have been placed onto skin abrasions, are harvested and analyzed for surface markers by flow cytometry and compared with PBL isolated at the same time (A. S. J. Marshall et al., manuscript in preparation) (Fig. 5A). The recruited myeloid populations could not be easily separated as they overlapped on FSC and SSC, but were identified by CD86 and CD15 staining into granulocytes (CD86CD15+) and macrophages (CD86+CD15) (data not shown; A. S. J. Marshall et al., manuscript in preparation). In comparison with the peripheral blood cells, βGR expression was maintained on recruited macrophages, but was slightly, but consistently, down-regulated on the recruited granulocytes (Fig. 5B). The decreased expression on recruited granulocytes may reflect βGR released on microvesicles, which have been shown to be induced upon granulocyte activation and which are capable of blocking cellular responses to zymosan 44, 45.

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Figure 5. Expression of βGR in an in vivo inflammatory model. (A) Histograms showing that βGR expression is maintained on monocyte/macrophages (MΦ; gated as CD86+CD15) but is decreased on granulocytes (Grn; gated as CD86CD15+). CD11b and CD86 are also shown as markers of activation for granulocytes and monocyte/macrophages, respectively. The gray histograms represent the isotype controls and the filled dark histograms represent specific antibody staining, as indicated, and the data are representative of three different donors. (B) Quantitation of GE2 expression levels, shown in (A) and represented as mean ± SD of data pooled from two independent donors.

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Overall, it is notable that there are differences in expression between human and mouse Dectin-1. In the mouse, expression of Dectin-1 appears to be more restricted and has not been detected on eosinophils or on B cells 24. Furthermore, in contrast to the murine receptor, the human βGR was not up-regulated on macrophages in culture or highly expressed on recruited inflammatory cells. Although the significance of these differences is unclear, they should be considered when utilizing the mouse as a model system for this receptor, once a knockout becomes available.

Function of the βGR on primary human macrophages

A number of receptors, including CR3 14, scavenger receptors 15 and lactosylceramide 16, have been proposed to recognize β-glucans on human leukocytes. As we had shown that Dectin-1 was the major β-glucan receptor on murine macrophages 7, we next examined the contribution of this receptor to zymosan recognition in human cells (Fig. 6A). Zymosan binding by monocyte-derived macrophages was significantly inhibited in the presence of GluP, indicating that the recognition of these particles is mainly mediated through β-glucan-dependent mechanisms. The ability of GE2, but not an isotype control, to inhibit zymosan recognition in an equivalent way to GluP demonstrated that the human βGR was responsible for this activity.

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Figure 6. Human Dectin-1 is the major βGR on monocyte-derived macrophages and contributes to the proinflammatory response to fungal particles. (A) Zymosan binding by day-7 matured monocyte-derived macrophages is β-glucan-dependent, as demonstrated by inhibition with GluP. Equivalent inhibition with GE2 demonstrates that this activity is mediated by the βGR. (B) TNF-α production in response to zymosan is β-glucan-dependent and requires the βGR. Shown is mean ± SD of data pooled and normalized from three independent donors in triplicate whose absolute TNF-α levels (pg/ml) were 231.00±8.95, 2236.00±70.44 and 1065.00±92.38. Macrophage TNF-α production was not detectable in the absence of zymosan.

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In murine macrophages, we have also shown that Dectin-1 collaborates with the TLR to induce proinflammatory cytokine production 4. To assess the role of the human βGR in this process, we incubated monocyte-derived macrophages with zymosan in the presence or absence of GluP, GE2 or an isotype control and assayed for the production of TNF-α. Although the absolute amount of TNF-α produced was donor variable, the presence of GluP or GE2, but not an isotype control, significantly inhibited TNF-α production in response to zymosan in all donors. Thus, like its murine homologue, the human βGR acts as the major receptor for β-glucans on macrophages and contributes to the inflammatory response to these particles.

It has also been reported that βGR are involved in the recognition of nontypeable Haemophilus influenzae in a variety of human cells, including monocytes and eosinophils 46, 47. The presence of Dectin-1 on both these cell types was suggestive that this receptor may be involved in the recognition of these organisms. However, we have been unable to demonstrate any interaction between this bacterium and either βGR-A or βGR-B (data not shown), suggesting that receptor(s) other than Dectin-1 are involved in this activity.

In summary, we have shown that human Dectin-1 is widely expressed on leukocytes and is not myeloid restricted. Although the expression patterns and regulation of the human βGR differs from those of the murine receptor, it appears to serve the same immune function. Future studies should address the identity of the endogenous ligand and the significance and roles of the alternatively spliced βGR isoforms.

Materials and methods

  1. Top of page
  2. Abstract
  3. Introduction
  4. Results and discussion
  5. Materials and methods
  6. Acknowledgements

Cells

To isolate peripheral leukocytes, blood was collected from healthy volunteers into EDTA (5 mM final concentration) and the erythrocytes were lysed using Gey's solution. The lysis solution was then layered onto 100% FCS and the intact leukocytes were collected by centrifugation and analyzed by flow cytometry, as described below. For the generation of macrophages and DC, human PBMC were isolated from buffy coats (Bristol Blood Donor Services) by centrifugation over a Ficoll-Paque™ PLUS (Amersham) gradient, according to standard procedures. Monocytes (day 0) were then purified by adherence for 1 h on gelatin-coated plates and by extensive washing to remove non-adherent cells. After a minimum 12-h incubation, monocytes (day 1) were harvested and then cultured in X-VIVO medium (BioWhittaker) with 1% heat-inactivated autologous serum to allow differentiation into macrophages, which were analyzed at day 4 and day 7.

For the generation of monocyte-derived DC, IL-4 (25 ng/ml; R&D Systems) and GM-CSF (50 ng/ml; R&D Systems) were added to day-1 monocytes in RPMI with 10% heat-inactivated FCS (RPMI medium), and then analyzed on day 4. To induce maturation of the DC, cells were cultured for a further two days in fresh medium with IL-4 and GM-CSF and then placed into media containing Salmonella typhimurium LPS (1 μg/ml; Sigma) and analyzed on day 8. All experiments were repeated on at least three different donors.

To generate inflammatory cells, a new in vivo inflammatory model was performed (A. S. J. Marshall et al., manuscript in preparation). In brief, a 2-cm2 area of skin on forearms from healthy adult volunteers was abraded with sandpaper until a small amount of capillary bleeding was obtained. This abrasion was then covered with a sterile PBS-moistened layer of filter paper, sealed using parafilm and left for 24 h. The filter paper was then replaced, and after a further 24 h the recruited cells attached to the filter paper were harvested into PBS containing 5 mM EDTA. These cells were compared with freshly isolated PBL from the same donor and analyzed by flow cytometery, as described below. All experiments were repeated on at least three different donors.

The generation of NIH3T3 fibroblasts expressing βGR-A or βGR-B has been described previously 10. NIH3T3 cells were cultured in DMEM with 10% FCS and G418 (0.6 mg/ml; Life Technologies) to maintain expression of the transduced genes.

Generation of mAb against human Dectin-1

The mAb (GE2 and BD6) were generated by immunization of C57BL/6 mice with NIH3T3 cells transduced with the full-length human βGR-A isoforms 10. Splenic B cells from immunized mice were then fused with the murine SP2 myeloma cell line, according to standard protocols 48. The mAb were initially selected based on their ability to specifically recognize cells transduced with βGR-A and subsequently by their ability/inability to stain cells transduced with βGR-B.

Flow cytometry

Cells were examined by three-color FACS analysis, performed according to conventional protocols at 4oC in the presence of 2 mM NaN3. Cells were blocked with PBS containing 5 mM EDTA, 0.5% BSA and 5.0% heat-inactivated rabbit serum (murine cells) or murine serum (PBL) and 50 μg/ml human IgG (Sigma; in vitro cultured human cells) prior to the addition of primary antibodies. Biotinylated antibodies were detected using streptavidin–allophycocyanin (BD Pharmingen). Cells were fixed with 1% formaldehyde, 0.25% BSA in PBS prior to analysis.

The following antibodies were used in these experiments: GE2–biotin, BD6–biotin, CD16 (Serotec), CD4 (CFAR), CD14–FITC (BD Pharmingen), CD16–PE (BD Pharmingen), CD56–PE (BD Pharmingen), CD19–PE (BD Pharmingen), DC-SIGN–FITC (BD Pharmingen), CD19–FITC (Caltag), CD1c (Serotec), BDCA2 49, CD8–PE (Serotec), CD83–PE (Serotec), CD3–FITC (Serotec), CD11b–FITC (Serotec), HLA-DR–FITC (Serotec), CD15–FITC (Serotec), and irrelevant biotin-, PE- or FITC-labeled mouse or rat IgG1 (D1.3; a gift from L. Martinez-Pomares, Oxford University), IgM (Serotec) and IgG2b (ECACC) control antibodies.

Fluorescent zymosan binding and TNF-α assays

The fluorescence-based binding assays using FITC-labeled zymosan with the NIH3T3 fibroblasts were performed essentially as described previously 10. For the assays involving human macrophages, isolated day-1 monocytes were plated in 24-well plates (4×105 cells/well) in X-VIVO medium with 1% heat-inactivated autologous sera, and incubated for six days at 37oC, to allow differentiation into macrophages, as described above. The cells were then thoroughly washed in ice-cold RPMI culture medium and placed at 4°C. Antibodies (50 μg/ml) or GluP (100 μg/ml) were added and the cells incubated for a further 1 h at 4oC, following which FITC-labeled zymosan (Molecular Probes; 25 particles/cell) was added and the cells incubated at 37oC for 30 min. After this incubation, unbound zymosan was removed by extensive washing and TNF-α or zymosan-binding assayed. For quantitation of TNF-α, the washed cells were incubated for a further 3 h in RPMI medium at 37°C, after which samples of supernatant were taken for TNF-α measurements. TNF-α was measured using the OptEIA human TNF-α ELISA kit (BD Pharmingen), as described by the manufacturers. For quantitation of zymosan-binding, cells were lysed with 3% triton X-100 and the FITC in the lysates was quantified using a Titretek Fluoroskan II [Labsystems Group (UK) Ltd]. The amount of fluorescence was normalized to the uninhibited control and expressed as percentage relative fluorescence. All experiments were repeated in triplicate on cells derived from at least three different donors.

Acknowledgements

  1. Top of page
  2. Abstract
  3. Introduction
  4. Results and discussion
  5. Materials and methods
  6. Acknowledgements

We would like to thank John Davies, Aron Chakera and Ashley Veldsman for help with the collection of blood samples, Joanna Miller, Eamon McGreal and Marc Mendelson for valuable reagents, and Philip Taylor for advice and critical reading of this manuscript. We also thank Brenda Jones (Institute of Animal Health, Compton, Berkshire, UK) for help in the generation and production of mouse anti-human-βGR mAb. The work was supported by the Edward Jenner Institute for Vaccine Research, the Histocytosis Association of America, the Wellcome Trust and the South African Medical Research Council. G. D. B. is a Wellcome Trust International Senior Research Fellow in Biomedical Science in South Africa.

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  • 1
    Janeway, C. A. Jr., The immune system evolved to discriminate infectious nonself from noninfectious self. Immunol. Today 1992. 13: 1116.
  • 2
    Underhill, D. M., Toll-like receptors: networking for success. Eur. J. Immunol. 2003. 33: 17671775.
  • 3
    van Kooyk, Y. and Geijtenbeek, T. B., DC-SIGN: escape mechanism for pathogens. Nat. Rev. Immunol. 2003. 3: 697709.
  • 4
    Brown, G. D., Herre, J., Williams, D. L., Willment, J. A., Marshall, A. S. J. and Gordon, S., Dectin-1 mediates the biological effects of β-glucan. J. Exp. Med. 2003. 197: 11191124.
  • 5
    Brown, G. D. and Gordon, S., Fungal β-glucans and mammalian immunity. Immunity 2003. 19: 311315.
  • 6
    Steele, C., Marrero, L., Swain, S., Harmsen, A. G., Zheng, M., Brown, G. D., Gordon, S., Shellito, J. E. and Kolls, J. K., Alveolar macrophage-mediated killing of Pneumocystis carinii f. sp. muris involves molecular recognition by the Dectin-1 β-glucan receptor. J. Exp. Med. 2003. 198: 16771688.
  • 7
    Brown, G. D., Taylor, P. R., Reid, D. M., Willment, J. A., Williams, D. L., Martinez-Pomares, L., Wong, S. Y. C. and Gordon, S., Dectin-1 is a major β-glucan receptor on macrophages. J. Exp. Med. 2002. 296: 407412.
  • 8
    Gantner, B. N., Simmons, R. M., Canavera, S. J., Akira, S. and Underhill, D. M., Collaborative induction of inflammatory responses by Dectin-1 and Toll-like receptor 2. J. Exp. Med. 2003. 197: 11071117.
  • 9
    Ariizumi, K., Shen, G. L., Shikano, S., Xu, S., Ritter, R. 3rd, Kumamoto, T., Edelbaum, D., Morita, A., Bergstresser, P. R. and Takashima, A., Identification of a novel, dendritic cell-associated molecule, dectin-1, by subtractive cDNA cloning. J. Biol. Chem. 2000. 275: 2015720167.
  • 10
    Willment, J. A., Gordon, S. and Brown, G. D., Characterisation of the human β-glucan receptor and its alternatively spliced isoforms. J. Biol. Chem. 2001. 276: 4381843823.
  • 11
    Hermanz-Falcon, P., Arce, I., Roda-Navarro, P. and Fernandez-Ruiz, E., Cloning of human DECTIN-1, a novel C-type lectin-like receptor gene expressed on dendritic cells. Immunogenetics 2001. 53: 288295.
  • 12
    Yokota, K., Takashima, A., Bergstresser, P. R. and Ariizumi, K., Identification of a human homologue of the dendritic cell-associated C-type lectin-1, dectin-1. Gene 2001. 272: 5160.
  • 13
    Grunebach, F., Weck, M. M., Reichert, J. and Brossart, P., Molecular and functional characterization of human Dectin-1. Exp. Hematol. 2002. 30: 13091315.
  • 14
    Ross, G. D., Thompson, R. A., Walport, M. J., Springer, T. A., Watson, J. V., Ward, R. H., Lida, J., Newman, S. L., Harrison, R. A. and Lachmann, P. J., Characterization of patients with an increased susceptibility to bacterial infections and a genetic deficiency of leukocyte membrane complement receptor type 3 and the related membrane antigen LFA-1. Blood 1985. 66: 882890.
  • 15
    Rice, P. J., Kelley, J. L., Kogan, G., Ensley, H. E., Kalbfleisch, J. H., Browder, I. W. and Williams, D. L., Human monocyte scavenger receptors are pattern recognition receptors for (1[RIGHTWARDS ARROW]3)-β-D-glucans. J. Leukoc. Biol. 2002. 72: 140146.
  • 16
    Zimmerman, J. W., Lindermuth, J., Fish, P. A., Palace, G. P., Stevenson, T. T. and DeMong, D. E., A novel carbohydrate-glycosphingolipid interaction between a β-(1–3)-glucan immunomodulator, PGG-glucan, and lactosylceramide of human leukocytes. J. Biol. Chem. 1998. 273: 2201422020.
  • 17
    Czop, J. K. and Kay, J., Isolation and characterization of β-glucan receptors on human mononuclear phagocytes. J. Exp. Med. 1991. 173: 15111520.
  • 18
    Mueller, A., Raptis, J., Rice, P. J., Kalbfleisch, J. H., Stout, R. D., Ensley, H. E., Browder, W. and Williams, D. L., The influence of glucan polymer structure and solution conformation on binding to (1[RIGHTWARDS ARROW]3)-β-D-glucan receptors in a human monocyte-like cell line. Glycobiology 2000. 10: 339346.
  • 19
    Mahauthaman, R., Howell, C. J., Spur, B. W., Youlten, L. J., Clark, T. J., Lessof, M. H. and Lee, T. H., The generation and cellular distribution of leukotriene C4 in human eosinophils stimulated by unopsonized zymosan and glucan particles. J. Allergy Clin. Immunol. 1988. 81: 696705.
  • 20
    Czop, J. K., Puglisi, A. V., Miorandi, D. Z. and Austen, K. F., Perturbation of β-glucan receptors on human neutrophils initiates phagocytosis and leukotriene B4 production. J. Immunol. 1988. 141: 31703176.
  • 21
    Di Renzo, L., Yefenof, E. and Klein, E., The function of human NK cells is enhanced by β-glucan, a ligand of CR3 (CD11b/CD18). Eur. J. Immunol. 1991. 21: 17551758.
  • 22
    Rylander, R. and Lin, R. H., (1[RIGHTWARDS ARROW]3)-β-D-glucan – relationship to indoor air-related symptoms, allergy and asthma. Toxicology 2000. 152: 4752.
  • 23
    Fogelmark, B., Thorn, J. and Rylander, R., Inhalation of (1[RIGHTWARDS ARROW]3)-β-D-glucan causes airway eosinophilia. Mediators Inflamm. 2001. 10: 1319.
  • 24
    Taylor, P. R., Brown, G. D., Reid, D. M., Willment, J. A., Martinez-Pomares, L., Gordon, S. and Wong, S. Y. C., The β-glucan receptor, Dectin-1, is predominantly expressed on the surface of cells of the monocyte/macrophage and neutrophil lineages. J. Immunol. 2002. 269: 38763882.
  • 25
    Wan, G. H., Li, C. S., Guo, S. P., Rylander, R. and Lin, R. H., An airbone mold-derived product, β-1,3-D-glucan, potentiates airway allergic responses. Eur. J. Immunol. 1999. 29: 24912497.
  • 26
    Czop, J. K. and Austen, K. F., A β-glucan inhibitable receptor on human monocytes: its identity with the phagocytic receptor for particulate activators of the alternative complement pathway. J. Immunol. 1985. 134: 25882593.
  • 27
    Czop, J. K., Fearon, D. T. and Austen, K. F., Opsonin-independent phagocytosis of activators of the alternative complement pathway by human monocytes. J. Immunol. 1978. 120: 11321138.
  • 28
    Passlick, B., Flieger, D. and Ziegler-Heitbrock, H. W., Identification and characterization of a novel monocyte subpopulation in human peripheral blood. Blood 1989. 74: 25272534.
  • 29
    Geissmann, F., Jung, S. and Littman, D. R., Blood monocytes consist of two principal subsets with distinct migratory properties. Immunity 2003. 19: 7182.
  • 30
    Sanchez-Torres, C., Garcia-Romo, G. S., Cornejo-Cortes, M. A., Rivas-Carvalho, A. and Sanchez-Schmitz, G., CD16+ and CD16 human blood monocyte subsets differentiate in vitro to dendritic cells with different abilities to stimulate CD4+ T cells. Int. Immunol. 2001. 13: 15711581.
  • 31
    Forsyth, C. B. and Mathews, H. L., Lymphocyte adhesion to Candida albicans. Infect. Immun. 2002. 70: 517527.
  • 32
    Nakagawa, Y., Ohno, N. and Murai, T., Suppression by Candida albicans β-glucan of cytokine release from activated human monocytes and from T cells in the presence of monocytes. J. Infect. Dis. 2003. 187: 710713.
  • 33
    Duan, X., Ackerly, M., Vivier, E. and Anderson, P., Evidence for involvement of β-glucan-binding cell surface lectins in human natural killer cell function. Cell. Immunol. 1994. 157: 393402.
  • 34
    Sobanov, Y., Bernreiter, A., Derdak, S., Mechtcheriakova, D., Schweighofer, B., Duchler, M., Kalthoff, F. and Hofer, E., A novel cluster of lectin-like receptor genes expressed in monocytic, dendritic and endothelial cells maps close to the NK receptor genes in the human NK gene complex. Eur. J. Immunol. 2001. 31: 34933503.
  • 35
    Mantegazza, A. R., Barrio, M. M., Moutel, S., Bover, L., Weck, M., Brossart, P., Teillaud, J. L. and Mordoh, J., CD63 tetraspanin slows down cell migration and translocates to the endosomal/lysosomal/MIICs route after extracellular stimuli in human immature dendritic cells. Blood 2004. 104: 11831190.
  • 36
    Reid, D. M., Montoya, M., Taylor, P. R., Borrow, P., Gordon, S., Brown, G. D. and Wong, S. Y., Expression of the β-glucan receptor, Dectin-1, on murine leukocytes in situ correlates with its function in pathogen recognition and reveals potential roles in leukocyte interactions. J. Leukoc. Biol. 2004. 76: 8694.
  • 37
    Mosser, D. M., The many faces of macrophage activation. J. Leukoc. Biol. 2003. 73: 209212.
  • 38
    Gordon, S., Alternative macrophage activation. Nat. Rev. Immunol. 2003. 3: 2335.
  • 39
    Romani, N., Gruner, S., Brang, D., Kampgen, E., Lenz, A., Trockenbacher, B., Konwalinka, G., Fritsch, P. O., Steinman, R. M. and Schuler, G., Proliferating dendritic cell progenitors in human blood. J. Exp. Med. 1994. 180: 8393.
  • 40
    Geijtenbeek, T. B., Torensma, R., van Vliet, S. J., van Duijnhoven, G. C., Adema, G. J., van Kooyk, Y. and Figdor, C. G., Identification of DC-SIGN, a novel dendritic cell-specific ICAM-3 receptor that supports primary immune responses. Cell 2000. 100: 575585.
  • 41
    Sallusto, F. and Lanzavecchia, A., Efficient presentation of soluble antigen by cultured human dendritic cells is maintained by granulocyte/macrophage colony-stimulating factor plus interleukin 4 and downregulated by tumor necrosis factor α. J. Exp. Med. 1994. 179: 11091118.
  • 42
    Willment, J. A., Lin, H. H., Reid, D. M., Taylor, P. R., Williams, D. L., Wong, S. Y. C., Gordon, S. and Brown, G. D., Dectin-1 expression and function is enhanced on alternatively activated and GM-CSF treated macrophages and negatively regulated by IL-10, dexamethasone and LPS. J. Immunol. 2003. 171: 45694573.
  • 43
    van der Merwe, P. A., Formation and function of the immunological synapse. Curr. Opin. Immunol. 2002. 14: 293298.
  • 44
    Gasser, O. S. and Schifferli, J. A., Activated polymorphonuclear neutrophils disseminate anti-inflammatory microparticles by ectocytosis. Blood 2004. 104: 25432548.
  • 45
    Hess, C., Sadallah, S., Hefti, A., Landmann, R. and Schifferli, J. A., Ectosomes released by human neutrophils are specialized functional units. J. Immunol. 1999. 163: 45644573.
  • 46
    Ahren, I. L., Williams, D. L., Rice, P. J., Forsgren, A. and Riesbeck, K., The importance of a β-glucan receptor in the nonopsonic entry of nontypeable Haemophilus influenzae into human monocytic and epithelial cells. J. Infect. Dis. 2001. 184: 150158.
  • 47
    Ahren, I. L., Eriksson, E., Egesten, A. and Riesbeck, K., Non-typeable Haemophilus influenzae activates human eosinophils through β-glucan receptors. Am. J. Respir. Cell. Mol. Biol. 2003. 29: 598605.
  • 48
    Kohler, G. and Milstein, C., Continuous cultures of fused cells secreting antibody of predefined specificity. Nature 1975. 256: 495497.
  • 49
    Dzionek, A., Fuchs, A., Schmidt, P., Cremer, S., Zysk, M., Miltenyi, S., Buck, D. W. and Schmitz, J., BDCA-2, BDCA-3, and BDCA-4: three markers for distinct subsets of dendritic cells in human peripheral blood. J. Immunol. 2000. 165: 60376046.