Extracellular adenosine 5'-triphosphate induces a loss of CD23 from human dendritic cells via activation of P2X7 receptors
Ronald Sluyter1 and
James S. Wiley1
1 Department of Medicine, University of Sydney, Level 5 South Block, Nepean Hospital, Penrith, NSW 2750, Australia
Correspondence to: R. Sluyter; E-mail: rons{at}med.usyd.edu.au
Transmitting editor: K. Inaba
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Abstract
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Dendritic cells (DC) express a number of P2X receptors including the P2X7/P2Z receptor whose activation by extracellular adenosine 5'-triphosphate (ATP) induces the influx of calcium, DC maturation, cytokine release and apoptosis. In B lymphocytes ATP induces the rapid shedding of CD23 and CD62 ligand by activating a membrane metalloprotease. In this study, we examined the expression and early effects of P2X7 receptor activation on monocyte-derived DC, generated from individuals either wild-type or homozygous for a loss-of-function single nucleotide polymorphism at position 1513 of the P2X7 gene. Labeling with an anti-human P2X7 receptor mAb demonstrated that DC express the P2X7 receptor at a lower level than macrophages. Short-term incubations (5 min) of DC with ATP induced an influx of ethidium+ (314 Da) into wild-type DC, but not into DC homozygous for the loss-of-function polymorphism. In contrast to results with ethidium+, ATP did not induce the influx of the viability dye propidium2+ (415 Da) into DC in short-term incubations. Addition of ATP also induced a rapid loss of CD23 from the surface of wild-type DC (t1/2 < 120 s), and this loss was inhibited by oxidized ATP and KN-62 which are known P2X7 receptor antagonists. Moreover, ATP-induced shedding of CD23 was slower from DC homozygous for the loss-of-function polymorphism than from wild-type DC. The data show that monocyte-derived DC express the P2X7 receptor whose activation opens a cation-selective channel, and which leads to rapid and near complete shedding of CD23. Both of these functions of the P2X7 receptor are impaired on DC from subjects who are homozygous for the loss-of-function 1513 polymorphism.
Keywords: cation channel, dendritic cell activation, IgE receptor, purinoceptor, single nucleotide polymorphism
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Introduction
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Dendritic cells (DC) are central in the initiation of adaptive immune responses (1,2), and there is considerable interest in understanding the mechanisms which govern the various stages of DC maturation and activation. CD23, the low-affinity receptor for IgE, has an emerging role in chronic inflammatory diseases including rheumatoid arthritis (RA) (3). CD23 expression can be induced on human Langerhans cells and peripheral blood DC by IL-4 (4,5), and CD23 is present on human DC differentiated from either monocytes or CD34+ hematopoietic progenitor cells in the presence of IL-4 and granulocyte macrophage colony stimulating factor (6,7), but is down-regulated upon DC maturation (7). Overnight culture of human Langerhans cells in the presence of IFN-
promotes the release of soluble CD23 (sCD23) (8); however, other factors which can cause a loss of CD23 from the cell surface of DC have not been described.
Extracellular nucleotides, via binding to P2X and P2Y purinoceptors, are recognized as important mediators in immune and inflammatory responses (9). Recent studies have shown that DC express mRNA for P2X1, P2X4, P2X5, P2X7, P2Y1, P2Y2, P2Y4, P2Y6 and P2Y11 receptors (10,11). Although there is some evidence supporting a role for functional P2Y receptors on DC (1214), most studies have centered around the function of the P2X7 receptor on DC. Activation of this receptor on murine and human DC by extracellular adenosine 5'-triphosphate (ATP) induces a number of downstream events including the influx of calcium, DC maturation, cytokine release and apoptosis (10,11,1518). We have shown that ATP can induce shedding of both CD23 and CD62 ligand from the surface of B lymphocytes via the P2X7 receptor (19,20); however, the early effects of P2X7 receptor activation on DC are less well defined. More recently, we have described a single nucleotide polymorphism at position 1513 of the P2X7 gene that codes for a glutamic acid to alanine substitution at amino acid position 496 which causes an almost complete loss-of-function of the P2X7 receptor on lymphocytes, monocytes and macrophages (2123). In this study, using DC generated from individuals either wild-type or homozygous for this loss-of-function polymorphism, we report that human DC express P2X7 receptors, and demonstrate for the first time that extracellular ATP induces a rapid and near complete loss of CD23 from the surface of DC via activation of P2X7 receptors.
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Methods
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Nucleotides and P2X7 receptor antagonists
ATP, 2'- and 3'-O-(4-benzoylbenzoyl)ATP (BzATP), adenosine 5'-O-(3-thiotriphosphate) (ATP-
-S), adenosine 5'-diphosphate (ADP),
,ß-methylene ATP, uridine 5'-triphosphate (UTP) and oxidized ATP (2',3'-dialdehyde ATP) were purchased from Sigma (St Louis, MO). KN-62 (1-[N,O-bis(5- isoquinolinesulphonyl)-N-methyl-L-tyrosyl]-4-phenylpiperazine) was from Research Biochemicals (Natick, MA).
DC and macrophages
Monocyte-derived DC were generated as previously described (24). Briefly, peripheral blood was collected in heparin from healthy volunteers who were either wild-type or homozygous for a loss-of-function polymorphic mutation in the P2X7 gene (21). Mononuclear cells were separated by gradient centrifugation using Ficoll-Paque Plus (Amersham Pharmacia, Uppsala, Sweden) and cultured for 2 h at 37°C/5%CO2 in RPMI 1640 containing 10% heat-inactivated FCS, 0.1 mM non-essential amino acids, 5.5 x 102 mM 2-mercaptoethanol, 1 mM L-glutamine, 5 µg/ml gentamycin and 10 mM HEPES (Life Technologies, Grand Island, NY). The non-adherent cells were removed and the plastic adherent cells (monocytes) cultured in complete media containing 800 U/ml granulocyte macrophage colony stimulating factor (generously provided by Schering-Plough, Baulkham Hills, Australia) and 500 U/ml IL-4 (R & D Systems, Minneapolis, MN) for 7 days. At days 3 and 6, 75% of the spent media was removed and replaced with fresh cytokine-supplemented media. DC were used at day 7. Monocyte-derived macrophages were generated from plastic adherent cells cultured in the presence of complete media containing 100 ng/ml IFN-
(Sigma) for 7 days as previously described (21).
DNA extraction and genotyping
Genomic DNA was extracted from peripheral blood cells and the genotype at 1513 of the P2X7 coding region was determined by DNA sequencing of PCR products as previously described (21).
Antibodies and immunolabeling
FITC-conjugated anti-CD1a, and phycoerythrin (PE)-conjugated anti-CD1a and CD23 mAb were obtained from BD Biosciences (San Diego, CA). FITC-conjugated anti-CD2, -CD14 and -CD19 mAb were purchased from Dako (Carpinteria, CA). Murine anti-human P2X7 receptor mAb (kindly provided by Drs Gary Buell and Ian Chessell) (25) was purified from clone L4 hybridoma supernatant by chromatography on Protein ASepharose Fast Flow and conjugated to FITC as described previously (26).
DC and macrophages (1 x 105) were labeled with fluorochrome-conjugated mAb and 7-aminoactinomycin D (Sigma) for 20 min, washed, and analyzed using a FACSCalibur flow cytometer and CellQuest Software (Becton Dickinson, San Jose, CA).
Fluorescent cation dye influx measurement by flow cytometry
To determine the effect of extracellular ATP on ethidium+ and propidium2+ influx into DC, time-resolved flow cytometry was used as previously described for macrophages (21). Briefly, 25 µM ethidium+ or propidium2+ (Sigma) was added to 5 x 105 DC, pre-labeled with FITC-conjugated anti-CD1a mAb, in 1 ml KCl medium (150 mM KCl, 5 mM D-glucose, 0.1% BSA and 10 mM HEPES, pH 7.5) at 37°C, followed 40 s later by the addition of 1 mM ATP. Data was acquired at 500 gated events/s on a FACSCalibur flow cytometer. The linear mean channel of ethidium+ fluorescence intensity for the gated DC population (based on forward and side scatter, and CD1a expression) over successive 5-s intervals was analyzed by WinMDI 2.7 software (developed by Joseph Trotter; http://www.scripps.edu) and plotted against time. P2X7 receptor function was quantitated as the difference in arbitrary units of area under the uptake curves in the presence and absence of ATP in the first 5 min of incubation.
Nucleotide-induced loss of CD23 surface expression
DC (1 x 105) were incubated for up to 15 min in 1 ml NaCl medium (145 mM NaCl, 5 mM KCl, 5 mM D-glucose, 0.1% BSA and 10 mM HEPES, pH 7.5) for BzATP or 1 ml KCl medium for all other nucleotides at 37°C in the presence or absence of extracellular nucleotide. In some experiments, DC were pretreated with 300 µM oxidized ATP in NaCl medium for 60 min at 37°C and washed before use. Alternatively, the inhibitor, KN-62, in KCl medium was added 15 min before the addition of ATP. Incubations with ATP or other nucleotides were terminated by adding 2 volumes of cold isotonic 10 mM MgCl2 medium (10 mM MgCl2, 145 mM NaCl, 5 mM KCl and 10 mM HEPES, pH 7.5), centrifugation and washing twice with PBS. CD23 surface expression was determined using immunofluorescence labeling. DC were analyzed by flow cytometry gated by forward and side scatter. In some experiments FITC-conjugated anti-CD2, -CD14 and -CD19 mAb were used to exclude lymphocytes and monocytes/macrophages from the DC gate. The level of CD23 expression was determined as the mean fluorescence intensity of relative CD23 expression minus the mean fluorescence intensity of the isotype control mAb binding. Results are presented as either the percentage of CD23 expression or the percentage loss of CD23 expression in the presence of nucleotide compared to CD23 expression in the absence of nucleotide.
Measurement of sCD23
DC (1 x 106) in 1 ml KCl medium were incubated for 15 min at 37°C in the presence or absence of 0.5 mM ATP. Incubations were terminated by adding 100 µl of 100 mM MgCl2 medium (100 mM MgCl2, 145 mM NaCl, 5 mM KCl and 10 mM HEPES, pH 7.5) and centrifugation. The supernatants were removed, centrifuged for 1 min at 8000 g and frozen at 80°C until required; the cells were washed and labeled for CD23 expression as above. The amount of sCD23 released into the supernatants was measured using a human sCD23 ELISA kit (Bender MedSystems, Vienna, Austria).
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Results
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Human DC express P2X7 receptors
A previous study has shown that human monocyte-derived DC express the P2X7 receptor as demonstrated by anti-P2X7 receptor mAb labeling of DC and the accumulation of ethidium+ into these cells in response to extracellular ATP (11). Consistent with this earlier study, labeling of day 7 monocyte-derived DC with anti-human P2X7 mAb and flow cytometric analysis shows that wild-type DC express P2X7 receptors on the cell surface (mean fluorescence intensity of 8.4 ± 1.0 SEM, n = 7; Fig. 1). This expression on DC is lower than that previously observed for human macrophages (21) and as shown in Fig. 1. The mean fluorescence intensity of P2X7 receptor expression on DC generated from two different subjects homozygous for the loss-of-function polymorphism at 1513 was 9.7 and 8.2.

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Fig. 1. P2X7 receptor expression on the surface of DC and macrophages. DC (solid line) or macrophages (broken line) generated from the same subject were stained with FITC-conjugated anti-P2X7 receptor or isotype control (thin line) mAb and analyzed by flow cytometry. One representative experiment of two.
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Addition of extracellular ATP to wild-type DC produced a rapid uptake of ethidium+ (314 Da) over 5 min as measured by time-resolved flow cytometry (mean arbitrary units of ethidium+ uptake of 13,988 ± 2318 SEM, n = 6; Fig. 2). In contrast, addition of ATP failed to induce the influx of ethidium+ into DC from two different subjects homozygous for the loss-of-function polymorphism (mean arbitrary units of ethidium+ uptake of 233 and 430; Fig. 2). Moreover, pre-exposure of wild-type DC to the P2X7 antagonist, oxidized ATP (27), reduced the ATP-induced ethidium+ uptake into DC by 92.3% (results not shown).

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Fig. 2. Extracellular ATP-induces uptake of ethidium+ into wild-type DC but not DC homozygous for the 1513 polymorphism. DC from subjects wild-type at 1513 (circles) or homozygous for the 1513 polymorphism (triangles) were labeled with CD1a mAb and suspended in KCl medium at 37°C. Ethidium+ (25 µM) was added, followed 40 s later by the addition of 1 mM ATP (arrow). Mean channel of cell-associated fluorescence was measured by time-resolved flow cytometry for DC incubated in the presence (solid symbols) or absence of extracellular ATP (open symbols). One representative experiment of two.
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ATP does not induce uptake of propidium2+
Differences have been reported between different leukocytes in the maximum size of P2X7 receptor permeants (9), therefore the uptake of the larger cation propidium2+ (415 Da) into wild-type DC was examined by time-resolved flow cytometry. In contrast to the result with ethidium+, DC were impermeable to propidium2+ in either the absence or presence of extracellular ATP for
5 min (Fig. 3). This data suggests that P2X7 receptor activation opens a cation-selective channel with a maximum size pass between 314 and 415 Da.

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Fig. 3. Extracellular ATP induces uptake of ethidium+ but not propidium2+ into DC. Wild-type DC were labeled with CD1a mAb and suspended in KCl medium at 37°C. Ethidium+ (circles) or propidium2+ (triangles) (both 25 µM) was added, followed 40 s later by the addition of 1 mM ATP (arrow). Mean channel of cell-associated fluorescence was measured by time-resolved flow cytometry for DC incubated in the presence (solid symbols) or absence of extracellular ATP (open symbols). One representative experiment of two.
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ATP induces the loss of CD23 via P2X7 receptor activation
We previously demonstrated that extracellular ATP can induce CD23 shedding from the surface of human B lymphocytes (19). Incubation of wild-type DC with ATP for 15 min at 37°C caused a near-complete loss of CD23 from these cells (mean percentage loss = 94.9% ± 1.4 SEM, n = 15; Fig. 4). Similar to B lymphocytes (19), this loss of CD23 was rapid, reaching completion within 10 min (Fig. 5). The half-time for loss of CD23 from wild-type DC by ATP was <120 s. Pre-incubation of wild-type DC with either 300 µM oxidized ATP or 10 µM KN-62, two known P2X7 receptor antagonists (27,28), inhibited the loss of CD23 induced by ATP by 73.5% (± 5.4 SEM, n = 3) and 59.0% (± 19.8 SEM, n = 3) respectively.

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Fig. 4. CD23 expression on the surface of DC is reduced by extracellular ATP. Wild-type DC were suspended in KCl medium at 37°C and incubated in the presence (solid line) or absence (broken line) of 0.5 mM ATP for 15 min. The incubation was stopped by the addition of MgCl2 medium and centrifugation. The DC were washed and stained with PE-conjugated anti-CD23 or isotype control (thin line) mAb and analyzed by flow cytometry. One representative experiment of 15.
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Fig. 5. Time course of extracellular ATP-induced loss of CD23 from DC. Wild-type DC (solid circles) or DC homozygous for the 1513 polymorphism (triangles) suspended in KCl medium at 37°C were incubated in the presence of 0.5 mM ATP. At the times indicated the incubations were stopped, and the DC stained with PE-conjugated anti-CD23 or isotype control mAb and analyzed by flow cytometry. Results for DC from five different subjects wild-type at 1513 are shown as the mean ± SEM. Results for DC from two different subjects homozygous for the 1513 polymorphism are shown as separate lines. The percentage loss of CD23 in the absence of ATP at 15 min was <8%.
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To confirm that P2X7 receptor activation was involved in the ATP-induced loss of CD23 from DC, DC were generated from subjects who were homozygous for the 1513 polymorphism. The ATP-induced loss of CD23 was significantly slower from DC homozygous for the loss-of-function polymorphism compared to wild-type DC (Fig. 5). This difference in CD23 loss was particularly obvious within 5 min after addition of ATP, with a mean loss of 21.7% from homozygous DC compared to 91.3% from wild-type DC.
Exposure of DC to the most potent P2X7 agonist, BzATP, resulted in a similar loss of CD23 from DC compared to ATP, while the partial P2X7 agonist, ATP-
-S was less effective at reducing the level of CD23 on DC (Table 1). In contrast, exposure to the nucleotides, which do not activate P2X7 receptors,
,ß-methylene ATP, ADP or UTP resulted in a minimal loss of CD23 from DC (Table 1).
ATP induces the shedding of CD23
To determine if the ATP-induced loss of CD23 from the surface of DC was due to the shedding of CD23, the release of sCD23 into the medium from wild-type DC incubated for 15 min in the absence or presence of 0.5 mM ATP was measured by ELISA. Incubation of DC without ATP resulted in a minimal release of sCD23 (Fig. 6). In contrast, incubation of DC with ATP resulted in a large release of sCD23 which corresponded with a loss of CD23 from the cell surface (Fig. 6).

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Fig. 6. Extracellular ATP induces the release of sCD23 from DC corresponding to a loss of surface CD23. Wild-type DC were suspended in KCl medium at 37°C and incubated in the absence or presence of 0.5 mM ATP for 15 min. The incubation was stopped by the addition of MgCl2 medium and centrifugation. The amount of sCD23 released into the medium was measured by ELISA (closed bars) and the level of CD23 surface expression on DC was analyzed by flow cytometry (open bars). Results for DC from three different subjects wild-type at 1513 are shown as the mean ± SEM.
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Discussion
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The results presented here support previous observations that the P2X7 receptor is expressed on human DC (10,11,15,18). The P2X7 receptor is also present on human T and B lymphocytes, NK cells, monocytes, and macrophages (21,26,29), where it has a role in the release of active IL-1ß, shedding of CD23 and CD62 ligand, killing of intracellular mycobacteria, and induction of apoptosis [reviewed in (9)].
Time-resolved flow cytometry was used to show that ethidium+ enters into wild-type DC, but not into DC homozygous for the loss-of-function single nucleotide polymorphism at position 1513 of the P2X7 gene, in response to extracellular ATP. We have previously reported similar results with lymphocytes, monocytes and macrophages (21). The loss-of-function polymorphism predicts for a glutamic acid to alanine substitution at amino acid position 496, which is located in the C-terminal tail of the receptor. A unique feature of the P2X7 receptor is its slow (1040 s) dilation to a pore following rapid (<1 s) opening of a cation-selective channel (30). The carboxyl tail of the P2X7 receptor is essential for this slow dilation (31) and the glutamic acid at 496 lies within a motif that shares homology with an ankryin repeat (32). Therefore, this motif may be important in the recruitment of other P2X7 monomers and/or accessory proteins necessary for pore formation (32).
ATP activation of the P2X7 receptor in wild-type DC caused an uptake of the 314-Da cation ethidium+ but not the 415-Da cation propidium2+. Similar results have been observed for human B lymphocytes and murine T lymphocytes (33,34). An earlier study suggested that the size pass of P2X7 receptors in macrophages is
900 Da since extracellular ATP was shown to permeabilize macrophages to fluorescent anion dyes up to 831 Da but not dyes 961 Da in size (35). However, the P2X7 receptor is a cation-selective channel whose activation is known to induce apoptosis and it is possible that these large anionic compounds entered the cell as a result of early lytic events.
The main result in this study is that extracellular ATP induces a rapid loss of CD23 from the cell surface of human DC and that this loss occurs via activation of P2X7 receptors. This finding is supported by both genetic and pharmacological evidence. Firstly, the ATP-induced CD23 loss was much slower from DC from subjects who were homozygous for the loss-of-function polymorphism in the P2X7 receptor than from wild-type DC. This difference did not appear to be due to a dissimilarity in the maturation state of the DC, as DC obtained from subjects of either genotype expressed similar levels of both CD1a (results not shown) and the P2X7 receptor. Secondly, KN-62, a specific antagonist for P2X7 receptors (28), inhibited the ATP-induced CD23 loss from DC. The concentration of KN-62 used to block ATP-induced shedding was higher than that previously required (19), as preliminary results showed that 1 µM caused only a 30.0% inhibition (results not shown) compared to 59.0% inhibition with 10 µM KN-62. This difference may be attributed to the binding of KN-62 to albumin in the medium, thus limiting its potency. Finally, CD23 was lost from the surface of DC in response to the P2X7 receptor agonists, ATP, BzATP and ATP-
-S, but a minimal amount was lost in response to the P2X1 receptor agonist
,ß-methylene ATP, and the P2Y receptor agonists, ADP and UTP. However, our data cannot exclude a minor role for other P2X receptors in the ATP-induced loss of CD23. This ATP-induced loss of CD23 was not totally impaired in DC homozygous for the polymorphism nor was the loss totally inhibited by KN-62 in wild-type DC. Furthermore, human monocyte-derived DC express mRNA for P2X1, P2X4 and P2X5 receptors (10,11).
The physiological significance of ATP-induced CD23 shedding from DC is not known. ATP is released from cells under various inflammatory conditions (9) and it has been proposed that ATP may act as a constitutive danger signal able to activate DC (36). Although it is unknown whether extracellular ATP caused the maturation and/or activation of DC in our experiments, ATP-induced loss of CD23 from DC may represent an early event in DC maturation and/or activation since CD23 is down-regulated upon maturation (7). Alternatively, ATP-induced shedding of CD23 may be important in inflammatory disease. Increased levels of sCD23 have been reported in various inflammatory diseases including RA [reviewed in (3)] and DC are present in the rheumatoid synovium where they may perpetuate RA (37). Moreover, neutralizing anti-CD23 antibodies can reduce the severity of disease in a murine model of human RA (38), while in another model of arthritis, the incidence and severity of disease was reduced in P2X7 receptor-deficient mice compared to wild-type mice (39). Therefore, it is conceivable that ATP-induced shedding of CD23 from DC via P2X7 receptors may be an important regulatory pathway and that alterations in this process may be important in the pathogenesis of inflammatory diseases such as RA.
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Acknowledgements
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We thank Dr Raj Ishri and Ms Shery Le (Sydney, Australia) for advice regarding DC cultures. We are grateful to Schering-Plough (Baulkham Hills, Australia) for generously providing granulocyte macrophage colony stimulating factor. We thank Dr Gary Buell (Geneva, Switzerland) and Dr Ian Chessell (Cambridge, UK) for their gift of mAb, as well as Mr Ben Gu for preparation of the L4 mAb and Dr Changping Li for performing additional genotyping. The support of the Leo & Jenny Foundation, the Community Health & Anti-tuberculosis Association, the National Health & Medical Research Council and the Cecilia Kilkeary Foundation is gratefully acknowledged.
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Abbreviations
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ADPadenosine 5'-diphosphate
ATPadenosine 5'-triphosphate
ATP-
-adenosine 5'-O-(3-thiotriphosphate)
BzATP2'- and 3'-O-(4-benzoylbenzoyl)ATP
DCdendritic cell
PEphycoerythrin
RArheumatoid arthritis
sCD23soluble CD23
UTPuridine 5'-triphosphate
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References
|
---|
- Hart, D. N. J. 1997. Dendritic cells: unique leukocyte populations which control the primary immune response. Blood 90:3245.[Free Full Text]
- Stockwin, L. H., McGonagle, D., Martin, I. G. and Blair, G. E. 2000. Dendritic cells: immunological sentinels with a central role in health and disease. Immunol. Cell Biol. 78:91.[ISI][Medline]
- Bonnefy, J.-Y., Plater-Zyberk, C., Lecoanet-Henchoz, S., Gauchat, J.-F., Aubry, J.-P. and Graber, P. 1996. A new role for CD23 in inflammation. Immunol. Today 17:418.[ISI][Medline]
- Bieber, T., Rieger, A., Neuchrist, C., Prinz, J. C., Rieber, E. P., Boltz-Nitulescu, G., Scheiner, O., Kraft, D., Ring, J. and Stingl, G. 1989. Induction of Fc
R2/CD23 on human epidermal Langerhans cells by human recombinant interleukin 4 and
interferon. J. Exp. Med. 170:309.[Abstract]
- Krauss, S., Mayer, E., Rank, G. and Rieber, E. P. 1993. Induction of the low affinity receptor for IgE (Fc
RII/CD23) on human blood dendritic cells by interleukin-4. Adv. Exp. Med. Biol. 329:231.[Medline]
- Steger, M. M., Maczek, C. and Grubeck-Lobenstein, B. 1996. Morphologically and functionally intact dendritic cells can be derived from the peripheral blood of aged individuals. Clin. Exp. Immunol. 105:544.[ISI][Medline]
- Herbst, B., Kohler, G., Mackensen, A., Veelken, H., Kulmburg, P., Rosenthal, F. M., Schaefer, H. E., Mertelsmann, R., Fisch, P. and Lindemann, A. 1996. In vitro differentiation of CD34+ hematopoietic progenitor cells toward distinct cell subsets of the Birbeck granule and MIIC-positive Langerhans cell and the interdigitating dendritic cell type. Blood 88:2541.[Abstract/Free Full Text]
- Bieber, T. and Delespesse, G. 1991. Gamma-interferon promotes the release of IgE-binding factors (soluble CD23) by human epidermal Langerhans cells. J. Invest. Dermatol. 97:600.[Abstract]
- Di Virgilio, F., Chiozzi, P., Ferrari, D., Falzoni, S., Sanz, J. M., Morelli, A., Torboli, M., Bolognesi, G. and Baricordi, O. R. 2001. Nucleotide receptors: an emerging family of regulatory molecules in blood cells. Blood 97:587.[Abstract/Free Full Text]
- Berchtold, S., Ogilvie, A. L. J., Bogdan, C., Muhl-Zurbes, P., Ogilvie, A., Schuler, G. and Steinkasserer, A. 1999. Human monocyte derived dendritic cells express functional P2X and P2Y receptors as well as ecto-nucleotidases. FEBS Lett. 458:424.[ISI][Medline]
- Ferrari, D., La Sala, A., Chiozzi, P., Morelli, A., Falzoni, S., Girolomoni, G., Idzko, M., Dichmann, S., Norgauer, J. and Di Virgilio, F. 2000. The P2 purinergic receptors of human dendritic cells: identification and coupling to cytokine release. FASEB J. 14:2466.[Abstract/Free Full Text]
- Liu, Q. H., Bohlen, H., Titzer, S., Christensen, O., Diehl, V., Hescheler, D. J. and Fleischmann, B. K. 1999. Expression and a role of functionally coupled P2Y receptors in human dendritic cells. FEBS Lett. 445:402.[ISI][Medline]
- Marriott, I., Inscho, E. W. and Bost, K. L. 1999. Extracellular uridine nucleotides initiate cytokine production by murine dendritic cells. Cell. Immunol. 102:163.
- Wilkin, F., Duhant, X., Bruyns, C., Suarez-Huerta, N., Boeynaems, J. M. and Robaye, B. 2001. The P2Y11 receptor mediates the ATP-induced maturation of human monocyte-derived dendritic cells. J. Immunol. 166:7172.[Abstract/Free Full Text]
- Coutinho-Silva, R., Persechini, P. M., Bisaggio, R. D. C., Perfettini, J.-L., De Sa Neto, A. C. T., Kanellopoulos, J. M., Motta-Ly, I., Dautry-Varsat, A. and Ojcius, D. M. 1999. P2Z/P2X7 receptor-dependent apoptosis of dendritic cells. Am. J. Physiol. 276:C1139.
- Mutini, C., Falzoni, S., Ferrari, D., Chiozzi, P., Morelli, A., Baricordi, O. R., Collo, G., Ricciardi-Castagnoli, P. and Di Virgilio, F. 1999. Mouse dendritic cells express the P2X7 purinergic receptor: characterization and possible participation in antigen presentation. J. Immunol. 163:1958.[Abstract/Free Full Text]
- Nihei, O. K., de Carvalho, A. C. C., Savino, W. and Alves, L. A. 2000. Pharmacologic properties of P2Z/P2X7 receptor characterized in murine dendritic cells: role on the induction of apoptosis. Blood 96:996.[Abstract/Free Full Text]
- Schnurr, M., Then, F., Galambos, P., Scholz, C., Siegmund, B., Endres, S. and Eigler, A. 2000. Extracellular ATP and TNF-
synergize in the activation and maturation of human dendritic cells. J. Immunol. 165:4704.[Abstract/Free Full Text]
- Gu, B., Bendall, L. J. and Wiley, J. S. 1998. Adenosine triphosphate-induced shedding of CD23 and L-selectin (CD62L) from lymphocytes is mediated by the same receptor but different metalloproteases. Blood 92:946.[Abstract/Free Full Text]
- Jamieson, G. P., Snook, M. B., Thurlow, P. J. and Wiley, J. S. 1996. Extracellular ATP causes loss of L-selectin from human lymphocytes via occupancy of P2Z purinoceptors. J. Cell Physiol. 166:637.[ISI][Medline]
- Gu, B. J., Zhang, W. Y., Worthington, R. A., Sluyter, R., Dao-Ung, P., Petrou, S., Barden, J. A. and Wiley, J. S. 2001. A Glu-496 to Ala polymorphism leads to loss of function of the human P2X7 receptor. J. Biol. Chem. 276:11135.[Abstract/Free Full Text]
- Wiley, J. S., Gu, B. J., Zhang, W. Y., Worthington, R. A., Dao-Ung, P., Shemon, A. N., Sluyter, R., Liang, S. and Barden, J. A. 2001. Genetic polymorphisms of the human P2X7 receptor and relationship to function. Drug Dev. Res. 53:72.[ISI]
- Wiley, J. S., Dao-Ung, L. P., Gu, B. J., Sluyter, R., Shemon, A. N., Li, C., Taper, J., Gallo, J. and Manoharan, A. 2002. A loss-of-function polymorphic mutation in the cytolytic P2X7 receptor gene and chronic lymphocytic leukaemia: a molecular study. Lancet 359:1114.[ISI][Medline]
- Sallusto, F. and Lanzavecchia, A. 1994. Efficient presentation of soluble antigen by cultured human dendritic cells is maintained by granulocyte/macrophage colony-stimulating factor plus interleukin-4 and down-regulated by tumor necrosis factor-
. J. Exp. Med. 179:1109.[Abstract]
- Buell, G., Chessell, I. P., Michel, A. D., Collo, G., Salazzo, M., Herren, S., Gretener, D., Grahames, C., Kaur, R., Kosco-Vilbois, M. H. and Humphrey, P. P. A. 1998. Blockade of human P2X7 receptor function with a monoclonal antibody. Blood 92:3521.[Abstract/Free Full Text]
- Gu, B. J., Zhang, W. Y., Bendall, L. J., Chessell, I. P., Buell, G. N. and Wiley, J. S. 2000. Expression of P2X7 purinoceptors on human lymphocytes and monocytes: evidence for nonfunctional P2X7 receptors. Am. J. Physiol. 279:C1189.
- Wiley, J. S., Chen, J. R., Snook, M. B. and Jamieson, G. P. 1994. The P2Z-purinoceptor of human lymphocytes: actions of nucleotide agonists and irreversible inhibition by oxidized ATP. Br. J. Pharmacol. 112:946.[Abstract]
- Gargett, C. E. and Wiley, J. S. 1997. The isoquinoline derivative KN-62 a potent antagonist of the P2Z-receptor of human lymphocytes. Br. J. Pharmacol. 120:1483.[Abstract]
- Sluyter, R., Barden, J. A. and Wiley, J. S. 2001. Detection of P2X purinergic receptors on human B lymphocytes. Cell Tissue Res. 304:231.[ISI][Medline]
- Wiley, J. S., Gargett, C. E., Zhang, W., Snook, M. B. and Jamieson, G. A. 1998. Partial agonists and antagonists reveal a second permeability state of human lymphocyte P2Z/P2X7 channel. Am. J. Physiol. 44:C1224.
- Surprenant, A., Rassendren, F., Kawashima, E., North, R. A. and Buell, G. 1996. The cytolytic P2Z receptor for extracellular ATP identified as a P2X receptor (P2X7). Science 272:735.[Abstract]
- Denlinger, L. C., Fisette, L., Sommer, J. A., Watters, J. J., Prabhu, U., Dubyak, G. R., Proctor, R. A. and Bertics, P. J. 2001. The nucleotide receptor P2X7 contains multiple protein- and lipid-interaction motifs including a potential binding site for bacterial lipopolysaccharide. J. Immunol. 167:4.
- Wiley, J. S., Chen, R. and Jamieson, G. P. 1993. The ATP4 receptor-operated channel P2Z of human lymphocytes allows Ba2+ and ethidium+ uptakeinhibition of fluxes by suramin. Arch. Biochem. Biophys. 305:54.[ISI][Medline]
- Chused, T. M., Apasov, S. and Sitkovsky, M. 1996. Murine T lymphocytes modulate activity of an ATP-activated P2Z-type purinoceptor during differentiation. J. Immunol. 157:1371.[Abstract]
- Steinberg, T. H., Newman, A. S., Swanson, J. A. and Silverstein, S. C. 1987. ATP4 permeabilizes the plasma membrane of mouse macrophages to fluorescent dyes. J. Biol. Chem. 262:8884.[Abstract/Free Full Text]
- Gallucci, S. and Matzinger, P. 2001. Danger signals: SOS to the immune system. Curr. Opin. Immunol. 13:114.[ISI][Medline]
- Pettit, A. R. and Thomas, R. J. 2000. Dendritic cells: the driving force behind autoimmunity in rheumatoid arthritis? Immunol. Cell Biol. 77:420.[ISI]
- Platerzyberk, C. and Bonnefoy, J. Y. 1995. Marked amelioration of established collagen-induced arthritis by treatment with antibodies to CD23 in vivo. Nat. Med. 1:781.[ISI][Medline]
- Labasi, J. M., Petrushova, N., Donovan, C., McCurdy, S., Lira, P., Payette, M. M., Brissette, W., Wicks, J. R., Audoly, L. and Gabel, C. A. 2002. Absence of the P2X7 receptor alters leukocyte function and attenuates an inflammatory response. J. Immunol. 168:6436.[Abstract/Free Full Text]