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Is Associated with Allergic Asthma and Enhanced IL-4 Receptor Function1
* Division of Allergy and Immunology, Department of Pediatrics, Children’s Hospital Medical Center, Cincinnati, OH 45229; and
Center for Genome Information, Department of Environmental Health, and
Division of Immunology, Department of Internal Medicine, University of Cincinnati Medical Center, Cincinnati, OH 45267
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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in the development of allergic inflammation
and its gene has been implicated in the genetics of asthma and atopy.
In this study, we examined the functional consequences of two of the
human IL-4R allelic variants that have been found to associate with
asthma and atopy. We examined the effects of each variant alone and in
combination on IL-4-dependent gene induction. We found that neither the
Q576R nor the I75V variants affected IL-4-dependent CD23 expression.
However, the combination of V75R576 resulted in expression of an
IL-4R with enhanced sensitivity to IL-4. We next examined the
genetics of five of the known IL-4R allelic variants in asthmatic
and nonatopic populations. Strikingly, the association of V75/R576 with
atopic asthma was greater than either allele alone and the association
of R576 with atopic asthma was dependent on the coexistence of V75. A
haplotype analysis revealed a single IL-4R haplotype that was
associated with allergic asthma, VACRS, further confirming the
importance of the V75 and R576 combination in the genetics of asthma.
This is the first report demonstrating that a functional alteration in
IL-4R requires the coexistence of two naturally occurring single
nucleotide polymorphisms (snps) in combination; neither snp alone is
sufficient. These data illustrate the importance of studying snps in
combination, because the functional significance of a given snp may
only be evident in a specific setting of additional snps in the same or
different genes. |
Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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25% chance of
developing asthma, and those whose mother and father both have asthma
may have as high as a 50% risk of disease (3). A study of
5864 Norwegian twins indicated that the relative risk of developing
asthma was 17.9 among twins whose identical co-twin had a
positive history of asthma, vs only 2.3 for fraternal twins
(4). In another study of Finnish twins, in families where
one of the parents was asthmatic, up to 87% of the susceptibility to
asthma was explained by genetic influences (5). Among
infants and young children who have wheezing with viral infections, a
personal history or a family history of allergy is the factor most
strongly associated with the development of asthma (6).
Several genes and chromosomal regions have been linked to atopy and
asthma, supporting the polygenic nature of these disorders.
IL-4, a pleiotropic cytokine produced by Th2 cells and mast cells, is a
central mediator of allergic inflammation. Along with IL-13, it is the
major cytokine responsible for the induction of IgE synthesis and,
furthermore, IL-4 acts on Th0 cells to promote their differentiation
into Th2 cells (7, 8). In hematopoietic cells, IL-4 exerts
its activities by interacting with a specific cell surface receptor
comprised of a binding component, IL-4R, and the common 
-chain,
which is shared by multiple cytokine receptors. In the absence of the
common -chain, IL-4 can use the type II IL-4R, comprised of IL-4R
and the IL-13R1 chain (9, 10). This receptor complex is
also the cognate functional receptor for IL-13 (10).
Although IL-13 shares many functions with IL-4, they also have distinct
roles. In parasitic infection models, IL-13 has a critical role in the
Th2-dependent expulsion of Nippostrongylus brasiliensis
(11) and IL-13 appears to be more important than IL-4 in
mucus hypersecretion (12). Furthermore, IL-13 has recently
been shown to be a key mediator of the allergic response independent of
IL-4 in mouse models whereby IL-13 blockade prevented allergen-induced
airway hyperresponsiveness (13, 14).
The genes for both IL-4 (15, 16) and IL-13 (17, 18) have been associated with asthma and atopy. Both IL-4 and
IL-13 use the -chain of the IL-4R (IL-4R) as a part of their
respective receptor systems. The gene for IL-4R represents an ideal
candidate gene for atopy susceptibility because of: 1) its pivotal role
in both IL-4 and IL-13 signaling, 2) its key role in allergic
inflammation by promoting IgE production and Th2 cell development, and
3) its location on chromosome 16, which has been linked to asthma
(19). Eight naturally occurring allelic variants of
IL-4R have been reported (20), and several of these
have been associated with atopy (21, 22). These variants
occur as the result of single nucleotide polymorphisms
(snps)3 in the coding
sequence of the gene for IL-4R that result in single amino acid
changes. Two of the IL-4R allelic variants that have been associated
in multiple studies with asthma and atopy are the I75V and Q576R
polymorphisms (numbering including the 25-aa signal peptide) (21, 22). These variants have been also been referred to as I50V and
Q551R in other studies that used numbering beginning with the mature
protein (23). Our laboratory found that the presence of
the R576 allele correlated with the severity of
asthma, and there appeared to be a gene dosage effect
(24). However, studies in other populations have failed to
find an association of atopy with these IL-4R variants (25, 26).
To understand the biologic consequences of these variants, it is
important to examine their functional consequences. Although studies
have been done examining the functional consequences of a particular
polymorphism in IL-4R in isolation (21, 26, 27, 28), no
studies thus far have examined the functional consequences of IL-4R
polymorphisms in combination as they occur in nature. Both the Q576R
and I75V polymorphisms are common and occur in combination in the
general population. Herein, we carefully examine the functional
consequences of these polymorphisms alone and in combination.
Furthermore, we also determine the allele frequencies of several
IL-4R polymorphic variants alone and in combination to
elucidate relationships between the genetics and the biology of
IL-4R variants in atopic and nonatopic populations.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Two hundred unrelated adult asthmatic patients were
prospectively recruited from allergy offices affiliated with the
University of Cincinnati Medical Center (Cincinnati, OH). Asthma was
diagnosed in accordance with the American Thoracic Society criteria by
demonstrating a 12% or greater increase in FEV1 after a bronchodilator
or after a 2-wk trial of oral corticosteroids (29, 30).
Pulmonary function testing was performed according to the 1994 revised
American Thoracic Society guidelines using Pneumedics Dataloop
(Norwalk, CT) (30). Subjects underwent skin prick testing
including positive and negative controls and a panel of 14 common
environmental Ags indigenous to the Ohio valley (ALK Laboratories,
Wallingford, CT). They were instructed to discontinue antihistamines
before skin testing in accordance with the published guidelines
(31). Patients were divided into atopic and nonatopic
groups based on the results of the skin tests. Those with positive
reactions (
3 mm wheal with erythema) to 1 or more Ags tested were
designated atopic. There were equal proportions (24%) of smokers (past
or present history) in the atopic and nonatopic asthma groups, and
there were no significant differences in smoking between the genotypic
groups. For the nonatopic, nonasthmatic control group, healthy,
unrelated volunteers were prospectively recruited from the employee
pool of University of Cincinnati Medical Center and Children’s
Hospital Medical Center (Cincinnati, OH). Individuals were excluded
from this group if they reported a history of allergies, asthma,
chronic cough, chronic obstructive pulmonary disease, or smoking. They
underwent skin prick testing as outlined above, and those who
demonstrated no positive reactions (excluding histamine) were included
in the control group. Informed consent was obtained from all
participants in these studies. These studies were approved by the
Children’s Hospital Medical Center Institutional Review Board.
Cells and reagents
A201.1 murine B cells, a gift from Dr. G. Milligan (Children’s
Hospital Medical Center), are derived from the parent line A20. The
cells are
B220+IgG+Ia+IgA-IgM-IgD-
and were originally derived from a BALB/c mouse. Cells were maintained
in complete RPMI, consisting of RPMI 1640 (Life Technologies, Grand
Island, NY) supplemented with 10% FBS (Life Technologies), 2 mM
L-glutamine (BioWhittaker, Walkersville, MD), 100 U/ml
penicillin, 100 µg/ml streptomycin (BioWhittaker), and 50 µM 2-ME
(Sigma-Aldrich, St. Louis, MO). Recombinant human and mouse IL-4 were
purchased from R&D Systems (Minneapolis, MN). Polyclonal
anti-Stat6 Ab, S-20, was purchased from Santa Cruz Biotechnology
(Santa Cruz, CA). FITC-coupled anti-murine CD23 Ab was purchased
from BD PharMingen (San Diego, CA).
[-32P]ATP was purchased from NEN (Boston,
MA). FITC-conjugated goat anti-rabbit IgG was purchased from
Southern Biotechnology Associates (Birmingham, AL).
cDNA constructs, site-directed mutagenesis, and expression vectors
Human IL-4R cDNA, obtained from Dr. J. Ryan (Virginia
Commonwealth University, Richmond, VA), was subcloned into the
mammalian expression vector pREP9 (Invitrogen, Carlsbad, CA).
Site-directed mutagenesis was performed using the Quickchange
mutagenesis kit from Stratagene (La Jolla, CA) according to the
manufacturer’s instructions. To generate the construct encoding R576,
the primers were
5'-CCACTGGCTATCGGGAGTTTGTACATGCGGTGGAGCAGG-3' and its reverse
complement, 5'-CCTGCTCCACCGCATGTACAAACTCCCGATAGCCACTGG-3'.
For Val75, the primers used were
5'-GCCCACACGTGTGTCCCTGAGAACAACGG-3' and its reverse complement,
5'-CCGTTGTTCTCAGGGACACACGTGTGGGC-3'. The cDNA constructs were
verified by DNA sequencing before transfection.
Transfection
A total of 5 x 106 A201.1 cells were
washed, resuspended in RPMI containing 20 µg of uncut
pREP9.humanIL-4R and pulsed with a Genepulser II
electroporation device (Bio-Rad, Melville, NY) set at 960 µF and 200
V. After electroporation, cells were grown for 24 h in 10 ml
complete RPMI, then selected for resistance to neomycin (G418 sulfate;
BioWhittaker) at 1000 µg/ml for 12–21 days, respectively. Cell
populations were screened by flow cytometry for CD23 surface expression
in response to stimulation with human IL-4 (10 ng/ml) for 48 h
and/or by staining with anti-IL-13R1-FITC Ab. Positive
transfectant pools were cloned by limiting dilution.
Scatchard analysis
Scatchard analyses were done as previously described (32). 125I-labeled recombinant human IL-4 was obtained from NEN.
EMSA
EMSA assays were performed as previously described (33). A 100-fold excess of unlabeled nucleotide (20 ng) was used in cold competition samples, and 1 µl of anti-Stat6 polyclonal Ab was added to supershift samples.
Flow cytometry
A201.1 cells (5 x 105) were washed in cold PBS with 1% FBS and stained with FITC-conjugated anti-mouse CD23 Ab (BD PharMingen) in the presence of anti-FcR Ab 2.4G2 (BD PharMingen) for 30 min on ice. Cells were washed in cold PBS with 1% FBS and analyzed on a FACScan or FACSVantage instrument (BD Biosciences, San Jose, CA).
Immunoprecipitation and immunoblotting
A201.1 cells (2 x 107) were pelleted by centrifugation at 20,000 x g at 4°C and reconstituted in immunoprecipitation lysis buffer (50 mM Tris (pH 8), 150 mM NaCl, 1% Nonidet P-40, 1 mM PMSF, 10 µg/ml leupeptin, 10 µg/ml aprotinin, 5 mM iodoacetamide, 1 mM sodium orthovanadate, 20 mM NaF, 1 mM EDTA). Cells were incubated on ice for 30 min and lysates were clarified by centrifugation at 20,000 x g for 20 min at 4°C. Soluble Stat6 was immunoprecipitated with anti-Stat6 polyclonal Ab followed by protein A/G plus agarose (Santa Cruz Biotechnology) as previously described (32). Briefly, precipitates were washed three times in immunoprecipitation lysis buffer, reconstituted in Laemmli buffer, and resolved by electrophoresis on 10% SDS-PAGE gels.
Proteins were transferred to nitrocellulose membranes and blocked overnight in block solution (20 mM Tris (pH 7.4), 150 mM NaCl, 3.1% BSA, 0.1% polyethylene glycol). Membranes were probed with anti-phosphotyrosine mAb PY20 (BD Transduction Laboratories, Lexington, KY) or anti-Stat6 polyclonal Ab. Bound Abs were detected by incubation with anti-mouse or anti-rabbit IgG Abs conjugated to HRP (BD Transduction Laboratories) followed by ECL using ECL substrate (Amersham, Arlington Heights, IL).
Genotyping of IL-4R snps
Genomic DNA was isolated from EDTA anti-coagulated whole blood using the GenomicPrep kit from Amersham Pharmacia Biotech (Piscataway, NJ). The Q576R and S786P variants were genotyped as previously described (24, 28). For the I75V snp, we attempted to use the primers and assay conditions described by Mitsuyasu et al. (21) to genotype the I75 and V75 alleles; however, we obtained ambiguous results with their protocol. Another Japanese group reported similar difficulties with this assay (25). The difficulty in distinguishing between these alleles stems from the proximity of the responsible missense mutation next to a splice acceptor site. Thus, to reliably distinguish between these alleles, we determined the intronic sequence upstream to the exon containing the I75V substitution. Using a proximal exonic 5' primer, we PCR amplified a 4-kb intron from genomic DNA. We sequenced this intron and designed primers using a 5' intronic primer (5'-GGAAGAGTCTGATGCGGTTCC-3') and a downstream 3' exonic primer (5'-CAGCCCACAGGTCCAGTGTATAG-3') to amplify a 207-bp segment containing the I75V mutation. Subsequent digestion of this fragment with MslI readily distinguished between the I75 and V75 variants, because the V75 mutation generates an additional MslI site. For genotyping of the E400A snp, the following primers were used: sense, 5'-CGTCTGCCTGTTGTGCTATGTCAG-3'; and antisense, 5'-AAAAGCCCCCATTCTCCTCTCC-3'. The 530-bp product was digested with Cac8I, which cuts twice in the R400 allele but only once in the C400 allele. For the C431R allele, the following primers were used: sense, 5'-GAAAAAGGGAGCTTCTGTGCATC-3'; and antisense, 5'-CGTCTCTGTGCAAGTCAGGTTGTC-3'. The 324-bp product was then digested with Tsp451, which cuts only in the presence of the R431 allele.
Statistical analyses
Fisher’s exact or 
2 tests were used to
test for statistically significant differences in snp allele
frequencies between patients and controls.
There are two main existing algorithms for inferring haplotypes based on unrelated genotype data of populations: one is described by Clark (34), and another is based on the expectation maximization algorithm (35, 36, 37). However, both algorithms have their limitations. For Clark’s method (34), its reliability needs to be improved when the level of recombination is large. In the expectation maximization algorithm, although assumptions such as random mating in the sample population are required, it also allows a "free" recombination scheme. Therefore, we used a new algorithm in the present studies to infer haplotypes. This algorithm begins with the four-gametes test to identify segments where no recombination has occurred, and the individual haplotype of each segment can be obtained quickly and reliably. Then the individual haplotypes combining all segments can be obtained by using the maximum parsimony principle. Frequencies of haplotypes at the population level, which can explain all individuals, are calculated by gene-counting method. This algorithm can also provide detailed recombination information among all pairs of loci.
The inferred haplotype frequencies between groups were analyzed in a
2 x C contingency table, where the 2
goodness-of-fit statistics were calculated, and the significance was
evaluated by exact test using shuffling method (generated by
104 random permutations of the data).
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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variants
To elucidate the functional consequences of specific IL-4R
amino acid substitutions, we developed an in vitro transfection model
system. IL-4 is absolutely species specific; thus, human IL-4 binds
only to human IL-4R and not to murine IL-4R, and murine IL-4
binds only to murine IL-4R (38). Furthermore, murine
cells transfected with human IL-4R cDNA gain the ability to bind and
respond to human IL-4 (39). We transfected the wild-type
human IL-4R cDNA into the murine B cell lymphoma cell line A201.1.
We chose the A201.1 cells for our studies because they displayed a
strong positive response to murine IL-4 (Fig. 1
B). Transfected cells
acquired the ability to respond to human IL-4, while untransfected
cells remained responsive only to murine IL-4. The transfectant pools
were cloned by limiting dilution and the clones were stable over time
(Fig. 1B). We generated human IL-4R cDNA constructs
encoding the different I75V and Q576R variant combinations by
site-directed mutagenesis as shown schematically in Fig. 1A.
The constructs were transfected into A201.1 cells and a minimum of
three clones were obtained expressing each of the variant IL-4R
combinations.
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on the transfectants approximated that
of the endogenous murine receptor. To ensure that the transfectants
express similar levels of IL-4R, we confirmed near equal levels of
human IL-4R expression by Scatchard analyses (Fig. 1
C and
data not shown). All clones expressed similar levels of surface human
IL-4R. Approximately 1600–1900 receptors per cell were detected and
displayed a Kd of 1.5–2 x
10-9 M-1 regardless of
the amino acid substitutions. Thus, the I75V and Q576R amino acid
substitutions do not alter the binding affinity of IL-4R.
V75R576 IL-4R is associated with enhanced receptor sensitivity
to IL-4
Next we investigated whether there were any differences in the
sensitivity of IL-4-dependent gene induction among the various
transfectants. Neither the Q576R (Fig. 2A) nor the I75V (Fig. 2B) substitution alone altered IL-4-dependent CD23
induction. However, the combination of V75 and R576 together resulted
in enhanced receptor function as evidenced by increased sensitivity to
IL-4 (Fig. 2C). The half-maximal dose for IQ, VQ, and IR
were 0.6, 0.6, and 1.2 ng/ml, respectively, while the half-maximal dose
for the VR transfectants was 0.22 ng/ml. While the maximal levels of
CD23 induction by IL-4 achieved were similar in all the transfectants,
increased sensitivity was observed in the presence of the VR
combination with a 3- to 5-fold shift in the dose-response curve.
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snps in asthmatic and
nonasthmatic populations
Next we examined how the functional data that we had obtained
correlated with the genetics of IL-4R in asthmatic populations. We
have previously shown that the Q576R IL-4R variant is significantly
associated with atopy (22) and with the severity of asthma
(24). However, the R576 mutation only resulted in enhanced
IL-4R function in the context of a valine at position 75. Thus, we
hypothesized that we would see a similar association between V75 and
R576 in a group of asthmatic and nonatopic individuals. We genotyped a
group of asthmatic (n = 200) and nonatopic controls
(n = 65) for I75V and Q576R. The asthmatic individuals
were further subdivided into allergic and nonallergic groups based on
the results of skin prick testing to 14 common environmental Ags. By
this criteria, 145 (72.5%) of the 200 asthmatics were atopic and 55
(27.5%) were nonatopic, which approximates published reports on the
prevalence of atopy in asthmatic patients (40, 41). The
data are summarized in Table I. The I75V
and Q576R polymorphisms were not in linkage disequilibrium. Q576R was
significantly associated with atopic asthma (p
= 0.015) but not nonatopic asthma. We found no association between I75V
alone and either atopic or nonatopic asthma.
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). We have found seven
individuals who are homozygous for both V75 and R576, supporting the
natural occurrence of this combination. In our transfectant data, we
found that the VR combination IL-4R was associated with enhanced
IL-4-dependent CD23 expression. To investigate whether the VR
combination was also significantly associated with asthma, we reasoned
that the V75 and R576 would need to be in the same IL-4R protein.
Thus, we divided the subjects into two groups: individuals with at
least a VR combination (VV/QR, IV/RR, VV/RR) and those without a VR
combination (II/RR, IV/QQ, II/QQ, II/QR, or VV/QQ). The heterozygote
individuals (IV/QR) in whom the V75 and R576 may or may not occur in
the same receptor protein were excluded from this analysis. We then
examined the percentage of individuals in these groups with atopic or
nonatopic asthma (Table II). Strikingly, we only observed a significant
association with atopic asthma in the presence of the VR combination.
When we examined the genotypes that yielded the IR combination IL-4R
(II/QR, IV/RR, II/RR), the association of R576 was barely significant
(p = 0.04). Thus, the association of V75/R576
with atopic asthma was greater than either allele alone and the
association of R576 with atopic asthma is dependent on the coexistence
of a valine at position 75.
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snps
Next, we wanted to better characterize the genetics of the
IL-4R snps and determine the most frequent haplotypes that were
associated with asthma in this population. To do this, we genotyped 193
of the asthmatic individuals (140 atopic and 53 nonatopic) and 56 of
the nonatopic controls for five known polymorphic variants in IL-4R
including I75V, E400A, C431R, Q576R, and S786P. The data summarizing
the allele frequencies of each of these allelic variants in our
populations are shown in Table III. The
R576 allele was significantly associated with atopic asthma
(p = 0.015), but no significant associations
were observed with any of the other alleles.
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haplotypes observed in these
populations, a haplotype analysis was performed (Table IV). Only one haplotype was found to be
significantly associated with atopic asthma and that was haplotype 6,
VACRS (V75, A400, C431, R576, S786). This further confirms that the V
at position 75 and the R at position 576 are important. The other
positions contain the wild-type amino acids, except the alanine at
position 400 (from a glutamic acid). Thus, this amino acid may act in a
concerted manner with the V75 and R576 combination.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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is
associated with enhanced IL-4R function. Transfectants expressing
the V75R576 IL-4R displayed enhanced sensitivity to IL-4. Neither
the V75 nor the R576 alone was associated with altered IL-4R
function. This observation is of wide general significance because it
illustrates the importance of examining the functional consequences of
snps in combination. A given snp may only be relevant in the context of
a second or a combination of additional snps in the same gene or other
genes. Furthermore, a given snp may have no effect individually or in
combination with a different set of snps. Genetic association studies
have often been difficult to interpret due to poor reproducibility in
other populations. One reason for this may be that a given genetic
variant may not be important unless it is in the context of a second
snp or additional snps. This would contribute to disparate results in
different populations.
We examined the frequencies of the I75V and Q576R polymorphisms in a
population of asthmatic and control individuals and found that the
V75R576 combination was significantly associated with atopic asthma in
a group of patients with asthma. Furthermore, the association of V75
and R576 combination with asthma was greater than the V75 or
R576 alleles alone. This agreed well with the functional
data in our transfectants where we found that the VR combination was
associated with an enhancement of IL-4R function that was greater
that either the V75 or R576 IL-4R alone. Our data agree with
previous reports, which found no change in IL-4R function with the
Q576R polymorphism alone (27). We performed a haplotype
analysis to identify the haplotypes that occurred in our populations
and to determine which, if any, of these haplotypes were associated
with atopy and/or asthma. We found that only haplotype was associated
with atopic asthma in our group, VACRS. The haplotype analysis that we
used has the advantage that it does not use a free recombination model
and thus is not dependent on Hardy-Weinberg equilibrium. Haplotype
analysis done in other populations have also revealed significant
associations between IL-4R haplotypes and asthma (23).
It will be important to study the functional consequences of each of
these associated haplotypes to elucidate the mechanisms underlying the
genetic associations and to verify the biologic relevance of these
associations. If there is no functional alteration in the context of
the implicated haplotype, there maybe a linkage disequilibrium with yet
unidentified polymorphisms, as suggested previously
(23).
Because IL-4R is also a component of the IL-13R complex, it is
important to examine the impact of the atopy-associated IL-4R
polymorphisms and haplotypes on IL-13 function. It remains possible
that the effect of the implicated IL-4R polymorphisms and haplotypes
may be more pronounced on IL-13 signaling given the central importance
of IL-13 in the development of asthma (13, 14). This is
further supported by the recent report demonstrating interactive
genetic effects between snps in IL-4R and the IL-13 promoter
(42). Relatively modest changes in IL-4R function
coupled with increases in ligand (IL-13) production by promoter
polymorphisms (17, 18) or ligand (IL-13) activity by
polymorphisms in the coding sequence (17) may result in a
large enough functional change to be biologically and genetically
relevant. Interpretation of functional studies of snps are difficult
because any one snp in isolation or even any combination of snps in a
single gene may lead to only a modest change in function. However,
combination of this modest change with additional changes in gene
products in the same pathway may result in a significant biologic
alteration. We have recently developed an in vitro model system to
study IL-13 signaling (33) and are currently using this
model to study the effects of atopy-associated IL-4R allelic
variants on IL-13 signaling.
Delineating the mechanisms underlying genetic associations with atopy
is critical to our understanding of the pathogenesis of atopic
disorders. In this report, we investigated the functional effects of 2
IL-4R snps in isolation and in combination. It is currently unclear
how the receptor mutations result in altered gene induction. Studies
are under way to explore this. Our initial experiments demonstrate that
the mechanism is more complex than a simple change in Stat6 activation
levels (our unpublished observations). Receptor activation may lead to
the activation of a nuclear phosphatase or another protein that
directly effects the life cycle of Stat6. Although important questions
remain, our data provide novel insights into the molecular mechanisms
of two atopy-associated IL-4R snps and into the IL-4 signaling.
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Acknowledgments |
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Footnotes |
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2 Address correspondence and reprint requests to Dr. Gurjit K. Khurana Hershey, Division of Allergy and Immunology, Children’s Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH 45229. E-mail address: Gurjit.Hershey{at}chmcc.org
3 Abbreviation used in this paper: snp, single nucleotide polymorphism.
Received for publication April 19, 2002. Accepted for publication May 17, 2002.
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References |
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)
HuIL-4R
) or the I75R576 (•) IL-4R