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Receptors on Human Monocytes by Th1 and Th2 Cytokines1
*
Department of Medicine, Hospital for Special Surgery and Weill Medical College of Cornell University, New York, NY 10021;
Laboratoire d’Immunologie Cellulaire et Clinique, Institut National de la Santé et de la Recherche Médicale Unité 255, Institut Curie, Paris, France; and
Fakultät für Chemie, Universität Bielefeld, Bielefeld, Germany
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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R on phagocytes. We report in this study that an inhibitory
receptor, FcRIIb2, is expressed on circulating human monocytes, and
when co-cross-linked with stimulatory FcR it down-regulates effector
function. FcRIIb2 expression is increased by IL-4 and decreased by
IFN-, in contrast to the activating receptor, FcRIIa, which is
increased by IFN- and decreased by IL-4. Thus, Th1 and Th2 cytokines
differentially regulate the opposing FcR systems, altering the
balance of activating and inhibiting FcR. The detection and cytokine
modulation of FcRIIb2 in human myeloid cells provide evidence of a
negative regulator of immune complex-mediated responses in human
phagocytes and offer a new approach to limit Ab-triggered inflammation
in autoimmune disease. |
Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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R, and the complement system. Although it is clear that tissue
damage requires activation of phagocytes through FcR, regulation of
the balance between stimulatory and inhibitory FcR by local
cytokines has not been characterized.
In the mouse, there are three families of FcR that may interact with
immune complexes. FcRI and FcRIII are multimeric receptors with
IgG-binding 
-chains and -chains containing a signaling
immunoreceptor tyrosine-based activation motif
(ITAM)3 (1, 2). In murine models of inflammation, activation responses
triggered by these stimulatory receptors are modulated by FcRIIb, a
family of single-chain receptors containing an immunoreceptor
tyrosine-based inhibitory motif (ITIM) in the cytoplasmic domain
(3, 4, 5). In vivo studies have demonstrated that
FcRIIB-deficient mice have augmented type I, II, and III
hypersensitivity reactions, whereas -chain-deficient mice, lacking
ITAM-bearing FcRs, are protected from the pathological consequences
of IgG-containing immune complexes (6, 7, 8). These results
obtained by targeted disruption of specific FcR genes in mice
have provided proof of concept that the balance of activating and
inhibitory FcR determines inflammatory effector cell function, and
they have raised the possibility that modulation of FcRIIB might
determine susceptibility and severity of immune complex-induced
disease. However, there are no reports of association between a
deficiency in inhibitory FcRIIb function and Ab-mediated human
diseases, such as systemic lupus erythematosus, autoimmune hemolytic
anemia, or Goodpasture’s syndrome. Indeed, the expression and
regulation of inhibitory FcR on human effector cells have not
previously been defined.
In humans, there are three types of FcRs capable of triggering
cellular activation (1, 2, 9). FcRI and FcRIIIa,
like their murine counterparts, are multichain receptors with ITAMs
present in -chain subunits. FcRIIa, unique to humans, is a
single-chain receptor with an ITAM. It is the most widely expressed
stimulatory human FcR, present on monocytes, neutrophils, platelets,
and dendritic cells, and it triggers phagocytosis, Ab-dependent
cytotoxicity, and release of inflammatory mediators.
Inhibitory human FcRs are encoded by the FcRIIB gene. There are
two transcripts of FcRIIB generated by alternative splicing,
FcRIIB1 and FcRIIB2 (10). They are single-chain
receptors with extracellular domains similar to FcRIIA and
cytoplasmic domains containing an ITIM (11, 12). In cells
transfected with cDNA encoding FcRIIB, coaggregation of FcRIIb
with ITAM-bearing receptors suppressed effector responses triggered by
B cell receptor (BCR), TCR, Fc
RI, and FcRs (5, 13).
This led to the prediction that inflammatory responses by human
phagocytes could be regulated by ITIM-bearing FcRs. Whereas mRNA for
FcRIIB1 and FcRIIB2 have been detected in transformed human cell
lines, FcRIIb protein has not been identified in primary human
phagocytes, and mechanisms to modulate expression of inhibitory FcR
were unknown (14).
With this study, we report the first evidence for FcRIIb2 protein
expression in human blood monocytes and polymorphonuclear leukocytes
(PMN), and we demonstrate the capacity of FcRIIb to inhibit
FcRI-mediated activation responses. Our results show that cytokines
differentially regulate the expression of the two opposing FcR
systems, altering the balance of ITAM- and ITIM-containing FcR. The
detection of FcRIIb2 in normal human myeloid cells provides evidence
for the presence of a negative regulator of immune complex-mediated
responses in phagocytes. Given that the ratio of activating and
inhibitory FcR may determine the magnitude and the threshold of
effector cell activation, these results suggest new approaches to
modulate Ab-triggered inflammation and tissue injury in autoimmune
disease.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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The anti-CD32 mAb clone FLI8.26 (unconjugated and FITC
conjugated) was purchased from Research Diagnostics (Flanders, NJ).
F(ab')2 and intact IgG of anti-CD64 mAb clone
22.2 (IgG1) were obtained from Medarex (Annandale, NJ).
Affinity-purified F(ab')2 of goat anti-mouse
Abs were obtained from Jackson ImmunoResearch (West Grove, PA).
Anti-pan FcRII receptor blotting mAb (clone II1A.5) as well as
anti-FcRIIb specific blotting Abs (clone II8D2) were previously
described (15). Isotype control mouse mAb IgG2b 
(MOPC141) was obtained from Sigma (St. Louis, MO). HRP-linked sheep
anti-mouse and donkey anti-rabbit Abs and ECL Western blotting
detection reagents were from Amersham Life Science (Arlington
Heights, IL).
Preparation of anti-FcRIIb Abs
A polyclonal Ab reactive with the intracellular (IC) domain of
FcRIIb (anti-FcRIIb IC) was prepared by hyperimmunization of
rabbits with a rGST fusion protein of the residues from the first to
the third IC domains of human FcRIIb1 (GST-IC). A RT-PCR fragment
obtained from FcRIIb1 cDNA was made by using the following
amplimers: 5'-GCTCTCCCAGGATACCCTGAGTGC-3' (sense) and
5'-AATACGGTTCTGGTC ATCAGGCTC-3' (antisense), and it was
cloned into pGEX-2T expression vector (Pharmacia Biotech, Uppsala,
Sweden) after addition of restriction sites. Expression of the GST-IC
protein in Escherichia coli was induced by isopropyl
-D-thiogalactoside, and the protein was
purified from periplasmic fraction by affinity chromatography on
glutathione agarose column (Sigma). The rabbit’s antiserum reacted
with FcRIIb1 and FcRIIb2, but not with FcRIIa, as shown by
Western blotting using A375 melanoma cells expressing recombinant
FcRIIa, FcRIIb1, or FcRIIb2, and using purified soluble
FcRIIa recombinant molecules (see Results)
(16).
Transfection
The cDNAs encoding human FcRIIa or FcRIIb2 were inserted
into an expression vector under the control of the Sr promoter in
PBR322 in which a resistance gene to zeocin was introduced (NT-zeo)
(17). For transfection, 50 µg cDNAs linearized by
ScaI were transfected by electroporation at 260 V and 960
µF into 5 x 106 A375, a human melanoma
cell line (ATCC). The transfectants were selected by culture with 500
µg/ml of zeocin (Cayla, Toulouse, France). To prepare A375 cells
expressing FcRIIb1, cells were transfected with cDNA encoding human
FcRIIb1 inserted in pKC3-derived expression vector. After selection
in G418 (2 mg/ml), transfectants expressing high levels of FcRIIb1
were cloned by micromanipulation and cultured in RPMI 1640 and 10% FCS
and G418 (0.5 mg/ml). A375 transfectants recovered after selection were
cloned as described previously (18). The expression of
recombinant receptors by cloned cells was assessed by indirect
immunofluorescence.
Preparation of cells
Leukocytes were isolated from the venous blood of healthy
volunteers by centrifugation on a discontinuous two-step Ficoll-Hypaque
gradient. PMN were isolated from the lower interface, and contaminating
erythrocytes were lysed. PMN purity was 99%, as determined by
CD16-bright CD56-negative staining. Monocytes were purified from the
upper interface and separated from other mononuclear cells using a
CD14-positive magnetic selection procedure (StemCell Technologies,
Vancouver, Canada), following manufacturer’s instructions. Monocyte
purity, defined as cells positive for CD64, was 96.4 ± 1.4%
(n = 7). The CD64-negative population was
CD3 positive. Cells were resuspended to 5 x
106/ml in RPMI 1640 + 10% FCS. For modulation of
FcR expression, monocytes were cultured with 400 U/ml IFN-
(Genzyme, Cambridge, MA) or 200 ng/ml human rIL-4 (R&D Systems,
Minneapolis, MN) for indicated periods of time. EBV-transformed B cell
lines were a gift from Dr. Mary K. Crow (Hospital for Special Surgery,
New York, NY). The human T cell line Jurkat was obtained from American
Type Culture Collection (Manassas, VA) and was cultured in RPMI 1640
media supplemented with 10% FCS, penicillin (100 U/ml), and
streptomycin (100 µg/ml). P388D1 cell transfectants expressing human
FcRI were a gift from Dr. Jeffrey Edberg (University of
Alabama, Birmingham, AL) and were cultured as described previously
(19).
RNA isolation and RT-PCR amplification
RNA was extracted with Trizol (Life Technologies) according to
the manufacturer’s recommended procedure. RNA concentrations were
determined spectrophotometrically. First strand cDNA was synthesized
from 1 µg total cell RNA using the Superscript II reverse
transcriptase kit (Life Technologies, Grand Island, NY). The reaction
was held at room temperature for 10 min, incubated at 42°C for 1
h, and then heated at 90°C for 10 min to terminate. The reaction
mixture was diluted 1:2 with 20 µl of 1x reverse-transcriptase
buffer for a final volume of 40 µl. Ten microliters of the diluted
cDNA mixture (or 2-fold dilutions of this quantity, where indicated)
were amplified in a total volume of 50 µl containing 1x PCR buffer
(Perkin-Elmer/Cetus, Norwalk, CT), 200 µM of dNTPs, 750 µM
MgCl2, 1 µM of 5'-sense primer, 1 µM of
3'-antisense primer, and 1.5 U AmpliTaq DNA polymerase
(Perkin-Elmer/Cetus). The primer pairs 1S (5'-ATG TCT CAG AAT GTA TGT
CCC AGA-3') and 224 M (5'-CTC AAA TTG GGC AGC CTT CAC-3') were
complementary to a region in the first signal exon and the first
cytoplasmic exon, respectively, specific for FcRIIA. The primer
pairs 2S (5'-GGA ATC CTG TCA TTC TTA CCT GTC-3') and 241 M (5'-CCC AAC
TTT GTC AGC CTC ATC-3') were complementary to a region in the first
signal exon and the second cytoplasmic exon of FcRIIB, respectively
(14). The mixture was amplified for 33 cycles using a
Perkin-Elmer Cetus GeneAmp PCR System 9600. The PCR products were
analyzed by gel electrophoresis on 2% agarose gels. Analysis of
FcRIIA and FcRIIB RNA levels in monocytes cultured under
different conditions was performed by densitometry (Molecular Dynamics,
Sunnyvale, CA). Human FcRIIB1 and FcRIIB2 cDNAs were kindly
provided by Dr. Jeffrey V. Ravetch (Rockefeller University, New York,
NY) (10).
Immunoprecipitation and Western blotting
Cells (4 x 107 cells/ml) were
suspended in RPMI buffer, pelleted, and solubilized in lysis buffer
(1% Nonidet P-40; 10% glycerol; 16 mM
Na2HPO4; 4 mM
NaH2PO4; 70 mM NaCl; 50 mM
NaF; 5 mM EDTA; 0.4 mM
Na3VO4; 10 µg/ml each
aprotinin, leupeptin, soybean trypsin inhibitor, and pepstatin A; and
500 µg/ml pefabloc, pH 7.4) for 1 h at 4°C. The lysates
(2 x 107 cells/sample) were
immunoprecipitated using specific Abs (0.5–1 µg purified Ab) and
protein G-Sepharose beads (30 µl) for 2 h at 4°C. The
immunoprecipitates were analyzed by SDS-PAGE on 9% polyacrylamide
gels. The samples were electrophoretically transferred to
nitrocellulose membranes. Membranes were blocked and incubated with
specific blotting Abs (1 µg/ml) or specific polyclonal rabbit
antiserum (1:1000 dilution), followed by polyclonal sheep
anti-mouse or donkey anti-rabbit Abs (0.25 µg/ml) conjugated
with HRP (Amersham Life Science). The reaction was developed with an
ECL Western blotting detection kit (Amersham Life Science). Analysis of
radiograms was performed by densitometry. Background values from each
gel were subtracted to normalize measurements. Values are expressed as
relative densitometric units. Levels of FcRIIa and FcRIIb2
expression in monocytes cultured under different conditions were
compared with paired t tests.
Phagocytosis assay
FcR-specific probes of phagocytosis were prepared as
previously described (20). Briefly,
F(ab')2 and intact mIgG1 of anti-FcRI mAb
(clone 22.2) were biotinylated with N-hydroxysuccinimide
(long chain)-biotin (Pierce, Rockford, IL). To demonstrate that the
biotinylated preparations of 22.2 F(ab')2 and
22.2 IgG had equal capacity to bind FcRI, we incubated P388D1
tranfectants expressing human FcRI with both biotinylated
anti-FcRI reagents, and stained cells with FITC-conjugated
F(ab')2 of goat anti-mouse IgG
F(ab')2 specific (Jackson ImmunoResearch). The
mean fluorescence intensity of 22.2 F(ab')2 was
33 ± 4, and that of 22.2 IgG was 38 ± 5. Bovine
erythrocytes (E) (5 x 108) were
biotinylated with sulfo-N-hydroxysuccinimide-biotin
(Pierce), washed, and saturated with streptavidin (Boehringer Mannheim,
Indianapolis, IN). Biotin-streptavidin-coated bovine erythrocytes (EBA)
(8 x 107) were coated with 0.25 µg of
biotinylated 22.2 F(ab')2 or 22.2 IgG1. For all
experiments, the extent of opsonization on EBA with 22.2
F(ab')2 and 22.2 IgG1 was determined by flow
cytometry with FITC-conjugated F(ab')2 of goat
anti-mouse IgG F(ab')2 specific (Jackson ImmunoResearch). Only
probes with similar opsonization densities were used for paired
experiments. EBA-22.2 F(ab')2 and EBA-22.2 IgG1
were labeled with PKH26 lipophilic dye (Sigma) according to
manufacturer’s instructions. The capacity of monocytes to internalize
the PKH26-labeled EBA-22.2 F(ab')2 or EBA-22.2
IgG1 target particles was measured using a flow cytometric assay
previously described (21).
Statistical analysis
Experiments were performed in a matched-triplet design to
compare the effect of control medium, IFN-, and IL-4 on FcR
expression at RNA and protein levels. The data are displayed as
mean ± SEM. The effects of cytokine modulation on FcR
expression and the effects of FcRIIb2 co-cross-linking on the
FcRI-mediated phagocytic capacity were analyzed using a paired
t test (two tailed). A probability of 0.05 was used to
reject the null hypothesis that there is no difference between the
conditions.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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RIIB2 transcripts in monocytes and PMN by RT-PCR
Human FcRIIB has two splice variants: FcRIIB1 and
FcRIIB2. They are identical, except that FcRIIB2 lacks the first
IC exon resulting in a 19-aa deletion in the FcRIIb2 cytoplasmic
region. (3, 10). The FcRIIB-specific primers amplify
both FcRIIB1 and FcRIIB2 transcripts. The FcRIIB2 splice
variant is 57 bp shorter (10, 14). To document the
capacity to detect the 852-bp band (FcRIIB1) and 795-bp band
(FcRIIB2), we amplified FcRIIB1 and FcRIIB2 cDNAs with
FcRIIB-specific primers (Fig. 1
, lanes 8 and 9).
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RII family transcripts are present in primary
monocytes and PMN, we analyzed RNA from these cells along with control
lymphoid cell lines, using RT-PCR with FcRIIA-, FcRIIB-, and
actin-specific primers (Fig. 1
). In monocytes (lanes
2–4) and PMN (lanes 5–6) from multiple donors,
the predominant FcRIIB transcript was FcRIIB2. Jurkat cells
(lane 1) had no detectable expression of FcRIIB
transcripts, and EBV-transformed B cells expressed only the FcRIIB1
isoform (lane 7). As expected, FcRIIA transcripts
were only detected in myeloid cells.
Detection of FcRIIb2 protein in monocytes and PMN by Western
blotting
To investigate the expression of FcRIIb protein by Western
blotting, we generated rabbit polyclonal Abs against the IC domain of
human FcRIIb fused to GST (anti-FcRIIb GST-IC). We used two
other mAbs: anti-pan FcRII mAb (II1A.5), which recognizes both
FcRIIa and FcRIIb isoforms, and anti-FcRIIb mAb (II8D2),
which recognizes an epitope (SDPNFSI) in the second extracellular
domain of FcRIIb1 and FcRIIb2 isoforms, but not FcRIIa
(15). As shown in Fig. 2, we
could distinguish FcRIIa and FcRIIb isoforms expressed in A375
melanoma cells when using combinations of these Abs. When cell lysates
from A375 cells transfected with vector alone or with cDNA encoding
human FcRIIA, or FcRIIB1, or FcRIIB2 were immunoprecipitated
with the anti-pan FcRII mAb (FLI8.26) and blots were probed with
anti-FcRIIb blotting mAb (II8D2) (Fig. 2, left), a
band of 
39 kDa was detected in A375 expressing human FcRIIb1 and
a band of 36 kDa was detected in A375 expressing human FcRIIb2.
No bands were detected in A375 cells transfected with vector alone or
in A375 cells expressing human FcRIIa. Thus, anti-FcRIIb mAb
(II8D2) specifically recognizes only FcRIIb isoforms. To demonstrate
the specificity of the rabbit anti-FcRIIb (GST-IC), the
experiment was repeated using this as the blotting reagent. The
anti-FcRIIb (GST-IC) polyclonal Ab reacted only with FcRIIb1
and FcRIIb2 isoforms (Fig. 2, middle). When cell lysates
from A375 cells expressing FcRIIa, FcRIIb1, or FcRIIb2 were
immunoprecipitated with the anti-pan FcRII mAb (FLI8.26) and
blots were probed with anti-pan FcRII mAb (II1A.5), FcRIIa
was detected as a 40-kDa band, and FcRIIb1 and FcRIIb2 isoforms
were detected as a 39- and 36-kDa band, respectively, demonstrating
that II1A.5 mAb recognizes both FcRIIa and FcRIIb isoforms in
Western blotting (Fig. 2, right).
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RIIb isoforms on circulating human
phagocytes, we used the Ab panel characterized in Fig. 2. Cell lysates
were immunoprecipitated with rabbit anti-FcRIIb (GST-IC), and
blots were probed with anti-FcRIIb blotting mAb (II8D2) (Fig. 3A). As expected, we detected
a prominent band of 39 kDa representing FcRIIb1 in
EBV-transformed B cells (Fig. 3A, lane 4) and no
specific bands in Jurkat cells (lane 1). In freshly
purified monocytes and PMN, we identified a 35-kDa protein representing
the FcRIIb2 isoform (lanes 2 and 3). In
previous studies, human rFcRIIB2 transfected in FcR-negative
hamster BHK-21 and murine IIA1.6 cell lines was recognized by II8D2 mAb
as a 37-kDa band (15). Cell-specific and species-specific
glycosylation patterns may explain the observed differences in
m.w.
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RIIb2 in human
phagocytes, we performed an alternate experiment in which cell lysates
were immunoprecipitated with the anti-pan FcRII mAb (FLI8.26)
and blots were probed with the pan-FcRII mAb II1A.5 (Fig. 3B) (15). As predicted from the RT-PCR, only
the FcRIIb1 isoform was present in EBV-transformed B cells (Fig. 3B, lane 4). Two bands were present in the
immunoprecipitates from monocytes (lane 2) and PMN
(lane 3): a wide 40-kDa band representing FcRIIa
and a 35-kDa band representing FcRIIb2 protein. No specific bands
were detectable in Jurkat cells (lane 1). No specific
bands were immunoprecipitated by isotype control mouse mAb IgG2b
(MOPC 141) (data not shown). These data indicate that FcRIIb2
protein is expressed in blood monocytes and PMN.
Differential regulation of FcRIIa and FcRIIb2
isoforms by IFN- and IL-4
In the course of performing experiments on purified monocytes from
12 different disease-free individuals, we noted variation in the
expression of FcRIIb2 as compared with FcRIIa. The observed
variability among different donors raised the possibility that FcRII
isoforms might be differentially regulated by cytokines. As the
expression of FcRI and the associated ITAM-containing -chain are
up-regulated by a prototypic Th1-type cytokine (IFN-) and inhibited
by a prototypic Th2-type cytokine (IL-4) (22, 23, 24), we
investigated whether these cytokines could modulate FcRIIB2 and
FcRIIA. RNA was extracted from freshly isolated monocytes, monocytes
cultured overnight in complete medium, or cultured in medium
supplemented with IFN- (400 U/ml) or IL-4 (200 ng/ml). Serial
dilutions of cDNA were amplified with FcRIIB-, FcRIIA-, and
actin-specific primers. FcRIIB2 RNA level increased minimally
following overnight culture as compared with freshly purified monocytes
(Fig. 4). Treatment with IL-4 increased
FcRIIB2 transcripts, whereas IFN- decreased FcRIIB2
transcripts (Fig. 4A). The effects of these cytokines on
FcRIIB2 RNA levels were consistent and statistically significant
(IL-4 vs control p = 0.002 and IFN- vs control
p = 0.01, n = 4 experiments) (Fig. 4B). The pattern of cytokine modulation of FcRIIA RNA was
different from that of FcRIIB2, and the effects were of lesser
magnitude. IL-4 treatment decreased FcRIIA RNA levels in monocytes
(p = 0.001, n = 4) and IFN-
increased FcRIIA expression (p = 0.02,
n = 4) (Fig. 4B). Thus, we observed distinct
and opposing patterns of regulation for FcRIIA and FcRIIB2 RNA in
human monocytes.
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RIIB2 RNA levels by
IFN- and IL-4 results in different levels of protein, monocytes were
cultured for different time periods in complete medium or medium
supplemented with IFN- or IL-4. Cell lysates were immunoprecipitated
and blotted with anti-FcRIIb (GST-IC). After 24 h in
culture with IFN-, FcRIIb2 protein levels were decreased compared
with those of cells cultured in control medium. At 72 h,
FcRIIb2 levels remained lower in monocytes cultured with IFN-
(Fig. 5A). In contrast, IL-4
treatment resulted in increased FcRIIb2 protein at 24 h. The
increase in FcRIIb2 protein with IL-4, relative to cells incubated
in control medium, continued at 48 h (data not shown) and was
even greater after 72 h of culture (Fig. 5A). Thus, the
differential modulation of FcRIIb2 protein by IL-4 and IFN-
persisted over the time interval studied.
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RIIb2 protein in relation to that of
FcRIIa, we repeated the experiment using anti-pan FcRII mAb
for immunoprecipitation and blotting (FLI8.26 and II1A5, respectively)
(Fig. 5B). Treatment with IL-4 decreased FcRIIa protein
and increased FcRIIb2 protein levels, while IFN- treatment
resulted in a modest induction of FcRIIa and a decrease in
FcRIIb2. The results of densitometric quantitation of FcRIIa and
FcRIIb2 protein levels obtained in a series of separate experiments
with different donors are shown in Fig. 5C. Although the
absolute magnitude of the differences in protein expression could not
be determined, the reciprocal cytokine regulation of FcRIIb2 and
FcRIIa was a consistent, reproducible, and statistically significant
finding. Taken together, the results of the RNA and protein studies
demonstrate opposing effects of prototypic Th1 (IFN-) and Th2 (IL-4)
cytokines on the expression of ITAM-containing FcRIIa and
ITIM-containing FcRIIb2 isoforms in human monocytes.
Inhibition of FcRI-mediated phagocytosis by FcRIIb2
coaggregation
Having demonstrated expression of FcRIIb2 on monocytes, we
sought to determine whether cocross-linking of FcRIIb2 with
stimulatory receptors on monocytes could attenuate surface
receptor-mediated activating signals. We investigated whether the
coclustering of FcRIIb2 would inhibit FcRI-mediated phagocytosis.
FcRI is constitutively expressed on monocytes and reacts
specifically with the mouse mAb 22.2 (mIgG1). Analogous to experiments
performed in B cells in which F(ab')2 of
anti-IgM were used to cross-link the BCR and intact IgG
anti-IgM Abs were used to coaggregate the BCR together with
FcRIIb1 (25, 26), we used E coated with
F(ab')2 of 22.2 mAb (EBA-22.2
F(ab')2) to cross-link FcRI alone and E coated
with intact 22.2 mIgG (EBA-22.2 IgG) to coaggregate FcRI with
FcRIIb2. We assessed the capacity of monocytes to bind and to
internalize these two types of target particles using a flow cytometric
assay. Attachment of EBA-22.2 IgG was slightly higher than that for
EBA-22.2 F(ab')2 (667 ± 173 vs 924 ±
281), but this difference did not reach statistical significance
(n = 7, p = 0.08) (Fig. 6, left). Despite similar or
increased attachment, in 9 of 10 disease-free donors, co-cross-linking
of FcRI and FcRIIb2 by EBA-22.2 IgG probes resulted in
significantly decreased phagocytosis as compared with that for EBA-22.2
F(ab')2 (954 ± 151 vs 654 ± 126,
n = 10, p = 0.01) (Fig. 6, right). We recognize that because of their similar binding
properties, FcRIIa as well as FcRIIb2 was bound by EBA-22.2 IgG;
yet the overall effects of co-cross-linking FcRI with FcRII
family members were negative. It is predicted that co-cross-linking of
only FcRI and FcRIIb2 would result in even greater inhibitory
effect. Our results indicate that FcRIIb2 functions as an inhibitory
receptor when coaggregated with ITAM-bearing FcR in human
phagocytes. It is likely that different levels of expression of ITAM vs
ITIM-containing FcR among individuals in our study determined
effector function.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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R by IgG-containing immune complexes initiates
signaling and elicits cellular responses. As most cells express more
than one type of FcR, interactions with immune complexes result in
coaggregation of different types of FcRs. Several activating FcR
are coexpressed on human phagocytes: FcRI and FcRIIa on
monocytes; FcRI, FcRIIa, and FcRIIIa on macrophages; and
FcRIIa and FcRIIIb on neutrophils (2, 9, 27).
Coclustering of different FcR was seen as a mechanism to potentiate
and amplify activation of effector cells. In this study, we report the
detection of an inhibitory FcR, FcRIIb2, in human blood monocytes
and PMN. Coaggregation of inhibitory and stimulatory FcR provides a
mechanism for down-modulation of inflammatory responses. Similar to the
inhibition of B cell activation and Ab production that occurs with
coligation of the BCR and FcRIIb1 (4, 5, 26), we
observed that co-cross-linking FcRIIb2 and FcRI inhibited the
monocyte phagocytic function. Preliminary studies indicate that
co-cross-linking FcRI with FcRIIb also inhibits mitogen-activated
protein kinase activation, suggesting that other monocyte functions are
also down-modulated by FcRIIb2. Thus, FcRIIb-mediated negative
regulation of ITAM-dependent cell activation endows IgG-containing
immune complexes with the capacity to regulate B cells and inflammatory
cells. The balance between stimulatory and inhibitory inputs determines
the cellular response.
Our findings indicate that FcRIIB2 is the predominant FcRIIB
transcript expressed in human monocytes and PMN. Prior studies have
detected FcRIIB1 and FcRIIB2 transcripts in monocytic cell lines
(14). Because some FcR transcripts defined at the RNA
level are not productively translated into proteins (28),
we analyzed the distribution of FcRII isoforms at the protein level.
Using a novel anti-FcRIIb (GST-IC) mAb for immunoprecipitation
and anti-FcRIIb-specific II8D2 mAb for blotting
(15), neither of which recognizes FcRIIa, we identified
FcRIIb2 as a 35-kDa band in monocytes and PMN. FcRIIb2, the
ITIM-bearing isoform, was coexpressed with the ITAM-containing
FcRIIa isoform. The ratio of activating FcRIIa and inhibitory
FcRIIb2 expressed on freshly isolated human monocytes varied
considerably among different donors. Given our findings that IFN-
decreased FcRIIb2 and increased FcRIIa, whereas IL-4 had the
opposite effect, the variability in relative expression of FcRII
isoforms among individuals may be related to differences in cytokine
milieu or cellular activation. Alternatively, there may be
polymorphisms within the promoter regions of these human FcRs, as
have been described for the FcRIIB promoter in autoimmune-prone
mouse strains, which could result in differential receptor expression
(29).
Engagement of monocyte FcR by immune complexes triggers the release
of reactive oxidants and inflammatory cytokines that modulate
inflammatory responses (7, 30, 31). That IFN- (a
prototypic Th1 cytokine) and IL-4 (a prototypic Th2 cytokine)
differentially regulate the expression of FcR isoforms with opposite
functions provides a mechanism for regulation of activating and
inhibitory signals delivered by FcRs on phagocytes. It has been
proposed that FcRIIb may function to modulate inflammatory responses
by determining the threshold of immune complex-stimulated activation of
macrophages (7, 32). During a Th2-driven response, IL-4
induction of inhibitory signaling through FcRIIb2 may limit immune
complex-triggered inflammatory responses. Alternatively, during a Th1
response, IFN- increases expression of ITAM-bearing FcR and
decreases expression of FcRIIb2, which may lower the threshold for
cellular activation and allow macrophages to deliver more potent
cytolytic responses.
Cytokine-mediated changes in FcR expression also have the potential
to regulate the afferent component of an immune response. In the
process of differentiation of monocytes into dendritic cells, FcRIIa
is down-regulated (33). We noted that IL-4 treatment,
which increases FcRIIb2, was accompanied by phenotypic changes
characteristic of dendritic cells. Taken together, it is likely that in
the presence of IL-4 there might be decreased uptake and presentation
of opsonized Ags by monocyte-derived dendritic cells, thus limiting
immune responses. That deletion of FcRIIB in mice results in
increased susceptibility to autoimmune disease supports this
possibility (32).
In autoimmune diseases, immune complex-mediated injury results from
recruitment of phagocytes to sites of IgG deposition and initiation of
a local inflammatory response. Phagocytosis of immune complexes is
associated with generation of respiratory burst, release of proteolytic
enzymes, and inflammatory mediators. In murine models, severe
autoimmune injury has been associated with decreased inhibition by
FcRIIb and unopposed activation through ITAM-expressing FcR on
macrophages (6, 32). Thus, it has been suggested that
strategies to up-regulate the FcRIIb-inhibitory pathway or
down-regulate the FcRIIa or FcR -chain pathways would reduce
IgG-triggered inflammatory responses. Our study provides the first
evidence that human monocytes express inhibitory FcR, and that the
magnitude of monocyte effector function may be modulated by
immunoregulatory factors that alter the balance of ITIM- and
ITAM-containing FcR. The understanding of expression, regulation,
and function of FcRIIb2 on human primary effector cells will enable
the study of its contribution to the pathophysiology of immune
complex-mediated human diseases such as systemic lupus erythematosus.
Taken together with the identification of cytokines that increase the
ratio of expression of inhibitory to stimulatory FcR, our findings
present a potential new approach for the treatment of chronic
autoimmune diseases.
|
Acknowledgments |
|---|
RIIA-, FcRIIB1-, and
FcRIIB2-transfected A375 cells; and Frederic Vely (CIML, Marseille,
France) for the FcRIIb-IC-GST fusion protein. |
Footnotes |
|---|
2 Address correspondence and reprint requests to Dr. Luminita Pricop, Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021.
3 Abbreviations used in this paper: ITAM, immunoreceptor tyrosine-based activation motif; BCR, B cell receptor; E, bovine erythrocyte; EBA, biotin-streptavidin-coated bovine erythrocytes; IC, intracellular; ITIM, immunoreceptor tyrosine-based inhibition motif; PMN, polymorphonuclear leukocytes.
Received for publication July 27, 2000. Accepted for publication September 29, 2000.
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References |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
R genes: duplication and recombination. Science 248:732.RIIB modulates B-cell receptor signalling. Nature 369:340.[Medline]
RIIB, regulates negatively BCR-, TCR-, and FcR-dependent cell activation. Immunity 3:635.[Medline]
RII (CD32) isoforms expressed in B lymphocytes. J. Immunol. 152:574.[Abstract]
receptor-mediated phagocytosis by a nonphagocytic Fc receptor. Blood 91:1762.RIIA, FcRIIB and FcRIIC in hematopoietic cells: analysis of transcripts. Mol. Immunol. 30:451.[Medline]
RII/CD32) that inhibits the binding of immune complexes to FcR+ cells. J. Immunol. 152:201.[Abstract]
RIII, but not FcRII, trigger serotonin release in rat basophilic leukemia cells. J. Immunol. 149:1365.[Abstract]
promoter: an efficient and versatile mammalian cDNA expression system composed of the simian virus 40 early promoter and the R-U5 segment of human T-cell leukemia virus type 1 long terminal repeat. Mol. Cell. Biol. 8:466.RIa alters the functional properties of the FcRI-chain receptor complex. J. Biol. Chem. 274:30328. receptor specific function. J. Immunol. Methods 148:179.[Medline]
R-specific probes. J. Immunol. Methods 205:55.[Medline]
RI expression and improved Fc-receptor-mediated phagocytosis after in vivo recombinant human interferon- treatment of normal human subjects. Blood 90:3187.R membrane expression and FcR-mediated cytotoxic activity of human monocytes. J. Immunol. 144:3046.[Abstract]
receptors and membrane immunoglobulin inhibits anti-immunoglobulin-induced blastogenesis. J. Immunol. 132:627.[Abstract]
receptor classes on human leukocytes. J. Exp. Med. 171:1333.RIb2 does not specify a surface-expressed isoform. Eur. J. Immunol. 29:143.[Medline]
RII. Curr. Biol. 10:227.[Medline]
receptor signaling and amplify phagocytic capacity. J. Immunol. 162:7041.RI and FcRII induces secretion of tumor necrosis factor by human monocytes, requiring high affinity Fc-FcR interactions: functional activation of FcRII by treatment with proteases or neuraminidase. J. Immunol. 144:1304.[Abstract]
receptor IIB renders H-2(b) mice susceptible to collagen-induced arthritis. J. Exp. Med. 189:187.. J. Exp. Med. 179:1109.This article has been cited by other articles:
|
|
 |
|
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|
|
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|
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|
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|
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|
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|
|
|
|
|
|
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|
|
|
|
|
|
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|
|
|
|
|
|
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|
|
|
|
|
|
E. van Mirre, W. B. Breunis, J. Geissler, C. E. Hack, M. de Boer, D. Roos, and T. W. Kuijpers Neutrophil responsiveness to IgG, as determined by fixed ratios of mRNA levels for activating and inhibitory Fc{gamma}RII (CD32), is stable over time and unaffected by cytokines Blood, July 15, 2006; 108(2): 584 - 590. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. Ai, A. Maturu, W. Johnson, Y. Wang, C. B. Marsh, and S. Tridandapani The inositol phosphatase SHIP-2 down-regulates Fc{gamma}R-mediated phagocytosis in murine macrophages independently of SHIP-1 Blood, January 15, 2006; 107(2): 813 - 820. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
N. Guriec, C. Daniel, K. Le Ster, E. Hardy, and C. Berthou Cytokine-regulated expression and inhibitory function of Fc{gamma}RIIB1 and -B2 receptors in human dendritic cells J. Leukoc. Biol., January 1, 2006; 79(1): 59 - 70. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T R D J Radstake, K C A M Nabbe, M H Wenink, M F Roelofs, A Oosterlaar, A W T van Lieshout, P Barrera, P L E M van Lent, and W B van den Berg Dendritic cells from patients with rheumatoid arthritis lack the interleukin 13 mediated increase of Fc{gamma}RII expression, which has clear functional consequences Ann Rheum Dis, December 1, 2005; 64(12): 1737 - 1743. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
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|
|
|
|
|
|
T R D J Radstake, A W T van Lieshout, P L C M van Riel, W B van den Berg, and G J Adema Dendritic cells, Fc{gamma} receptors, and Toll-like receptors: potential allies in the battle against rheumatoid arthritis Ann Rheum Dis, November 1, 2005; 64(11): 1532 - 1538. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
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|
|
|
|
|
|
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|
|
|
|
|
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|
|
|
|
|
|
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|
|
|
|
|
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|
|
|
|
|
|
T R D J Radstake, A B Blom, A W Sloetjes, E O F van Gorselen, G J Pesman, L Engelen, R Torensma, W B van den Berg, C G Figdor, P L E M van Lent, et al. Increased Fc{gamma}RII expression and aberrant tumour necrosis factor {alpha} production by mature dendritic cells from patients with active rheumatoid arthritis Ann Rheum Dis, December 1, 2004; 63(12): 1556 - 1563. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
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|
|
|
|
|
|
K. Su, J. Wu, J. C. Edberg, X. Li, P. Ferguson, G. S. Cooper, C. D. Langefeld, and R. P. Kimberly A Promoter Haplotype of the Immunoreceptor Tyrosine-Based Inhibitory Motif-Bearing Fc{gamma}RIIb Alters Receptor Expression and Associates with Autoimmunity. I. Regulatory FCGR2B Polymorphisms and Their Association with Systemic Lupus Erythematosus J. Immunol., June 1, 2004; 172(11): 7186 - 7191. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
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|
|
|
|
 |
|
 A. L. Hepburn, J. C. Mason, and K. A. Davies Expression of Fc{gamma} and complement receptors on peripheral blood monocytes in systemic lupus erythematosus and rheumatoid arthritis Rheumatology, May 1, 2004; 43(5): 547 - 554. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. R. Clatworthy and K. G.C. Smith Fc{gamma}RIIb Balances Efficient Pathogen Clearance and the Cytokine-mediated Consequences of Sepsis J. Exp. Med., March 1, 2004; 199(5): 717 - 723. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. U. Lutz, P. Stammler, V. Bianchi, R. M. Trueb, T. Hunziker, R. Burger, E. Jelezarova, and P. J. Spath Intravenously applied IgG stimulates complement attenuation in a complement-dependent autoimmune disease at the amplifying C3 convertase level Blood, January 15, 2004; 103(2): 465 - 472. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
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|
|
|
|
|
|
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|
|
|
|
|
|
Z.-Y. Huang, S. Hunter, M.-K. Kim, Z. K. Indik, and A. D. Schreiber The effect of phosphatases SHP-1 and SHIP-1 on signaling by the ITIM- and ITAM-containing Fc{gamma} receptors Fc{gamma}RIIB and Fc{gamma}RIIA J. Leukoc. Biol., June 1, 2003; 73(6): 823 - 829. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Tridandapani, R. Wardrop, C. P. Baran, Y. Wang, J. M. Opalek, M. A. Caligiuri, and C. B. Marsh TGF-{beta}1 Suppresses Myeloid Fc{gamma} Receptor Function by Regulating the Expression and Function of the Common {gamma}-Subunit J. Immunol., May 1, 2003; 170(9): 4572 - 4577. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Wijngaarden, J. A. G. van Roon, J. W. J. Bijlsma, J. G. J. van de Winkel, and F. P. J. G. Lafeber Fc{gamma} receptor expression levels on monocytes are elevated in rheumatoid arthritis patients with high erythrocyte sedimentation rate who do not use anti-rheumatic drugs Rheumatology, May 1, 2003; 42(5): 681 - 688. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. W. Morgan, V. H. Keyte, S. J. Babbage, J. I. Robinson, F. Ponchel, J. H. Barrett, B. B. Bhakta, S. J. Bingham, M. H. Buch, P. G. Conaghan, et al. Fc{gamma}RIIIA-158V and rheumatoid arthritis: a confirmation study Rheumatology, April 1, 2003; 42(4): 528 - 533. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. Garcia-Garcia and C. Rosales Signal transduction during Fc receptor-mediated phagocytosis J. Leukoc. Biol., December 1, 2002; 72(6): 1092 - 1108. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. Nakamura, A. Malykhin, and K. M. Coggeshall The Src homology 2 domain-containing inositol 5-phosphatase negatively regulates Fcgamma receptor-mediated phagocytosis through immunoreceptor tyrosine-based activation motif-bearing phagocytic receptors Blood, October 16, 2002; 100(9): 3374 - 3382. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Tridandapani, Y. Wang, C. B. Marsh, and C. L. Anderson Src Homology 2 Domain-Containing Inositol Polyphosphate Phosphatase Regulates NF-{kappa}B-Mediated Gene Transcription by Phagocytic Fc{gamma}Rs in Human Myeloid Cells J. Immunol., October 15, 2002; 169(8): 4370 - 4378. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. N. Damle, F. Ghiotto, A. Valetto, E. Albesiano, F. Fais, X.-J. Yan, C. P. Sison, S. L. Allen, J. Kolitz, P. Schulman, et al. B-cell chronic lymphocytic leukemia cells express a surface membrane phenotype of activated, antigen-experienced B lymphocytes Blood, May 13, 2002; 99(11): 4087 - 4093. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Tridandapani, K. Siefker, J.-L. Teillaud, J. E. Carter, M. D. Wewers, and C. L. Anderson Regulated Expression and Inhibitory Function of Fcgamma RIIb in Human Monocytic Cells J. Biol. Chem., February 8, 2002; 277(7): 5082 - 5089. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G Fossati, R C Bucknall, and S W Edwards Insoluble and soluble immune complexes activate neutrophils by distinct activation mechanisms: changes in functional responses induced by priming with cytokines Ann Rheum Dis, January 1, 2002; 61(1): 13 - 19. [Abstract] [Full Text] [PDF]
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