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* Division of Cell Biology, Department of Pediatrics, National Jewish Medical and Research Center, Denver, CO 80206; and
Wyeth Genetics Institute, Andover, MA 01810
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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2-IgG fusion protein (sIL-13R2Fc) on
days 71–72 for the early and late responses and on days 71–73 for the
development of AHR. sIL-13R2Fc administration inhibited the late,
but not early, phase response and the OVA challenge-induced changes in
lung resistance and dynamic compliance; as well, sIL-13R2Fc
administration decreased bronchoalveolar lavage eosinophilia and
mucus hypersecretion following the secondary challenge protocols. These
results demonstrate that targeting IL-13 alone regulates airway
responses when administrated to mice with established allergic airway
disease. These data identify the importance of IL-13 in the development
of allergen-induced altered airway responsiveness following airway
challenge, even when administered before rechallenge of mice in which
allergic disease had been previously
established. |
Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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RII) expression
on B cells and monocytes, chemokine production, activation of mast
cell, eosinophil, and neutrophil function, as well as the inhibition of
proinflammatory gene expression by monocyte/macrophage populations
(8, 11, 12, 13, 14, 15). IL-13 also increases expression of VCAM-1 on
endothelial cells, facilitating the preferential recruitment of
eosinophils (and T cells) to the airway tissues (16), and
airway mucus secretion, which can exacerbate airway responsiveness
(8, 17). Although not necessary for, or even capable of
inducing Th2 development, IL-13 plays a regulatory role in Th2 cell
activation (18), and in Th1 differentiation indirectly
through its down-regulatory effects on production of proinflammatory
cytokines, particularly on monocyte production of IL-12
(19). Administration of IL-13, or over expression of IL-13
in the airways, induced airway eosinophilia, mucus production, and AHR
to various degrees (4, 7, 8).
The role of IL-4 in allergen-induced AHR development has been
extensively studied. Using neutralizing Ab to IL-4 administered during
the sensitization phase, or in mice deficient in IL-4, the development
of airway eosinophilia, AHR, and increases in serum IgE seen following
sensitization and allergen provocation are markedly reduced or
abolished (20, 21, 22). However, administration of Ab to IL-4
after sensitization but during the allergen challenge phase only
partially reduces the response suggesting alternate mechanisms or even
a sequential requirement for IL-4 then IL-13 (20, 21, 23).
Inhibition of both IL-4 and IL-13-transduced signals in
STAT-6-deficient mice or in mice treated at the time of the challenge
with an IL-4R antagonist inhibited AHR and airway eosinophilia,
suggesting the importance of blocking not only IL-4 but also IL-13
(24, 25). The activity of IL-13 can be specifically
blocked by administration of a soluble fusion protein comprised
of the extracellular domain of the IL-13 high affinity receptor
(IL-13R2) fused to the Fc portion of human IgG1, which specifically
binds to and neutralizes IL-13 (26). Blockade of IL-13 at
the time of allergen challenge in this way inhibited OVA-induced AHR
with variable results on bronchoalveolar lavage (BAL) eosinophila
(4, 6, 7).
To date, most of the studies investigating the role of IL-13 have been performed in models of primary allergen challenge and the role of IL-13 in already established allergic airway disease is not well-defined. In patients with allergic asthma, allergen challenge leads to an early phase response (EPR), occurring within 15–30 min following allergen challenge. About 60% of patients also develop a late phase response (LPR), occurring about 3–5 h after allergen challenge, and characterized by airway obstruction and increased airway inflammation (27, 28). Similarly in mice with already established airway disease, allergen challenge can evoke EPR and LPR (29), followed by the development of sustained AHR (30). We previously showed important differences when a primary challenge approach was compared to mice which had previously been sensitized and challenged and later provoked with a single airway challenge (secondary challenge) (30). We also showed that lung resistance (RL, thought to reflect central airway function) and dynamic compliance (Cdyn; thought to reflect peripheral airway function) are differentially regulated in the latter model (30). The aim of the present study was to evaluate the role of IL-13 on airway function and lung inflammation in a model of allergen-induced AHR after re-exposure to allergen in previously sensitized mice assessed by monitoring EPR and LPR and the development of AHR.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Female BALB/cByJ mice were obtained from The Jackson Laboratory (Bar Harbor, ME). The mice were maintained on OVA-free diets. All experimental animals used in this study were under a protocol approved by the Institutional Animal Care and Use Committee of the National Jewish Medical and Research Center (Denver, CO).
Experimental protocol
Ten- to 12-wk-old mice were sensitized by i.p. injection of 20 µg of OVA (Grade V; Sigma-Aldrich, St. Louis, MO) emulsified in 2.25 mg of aluminum hydroxide (AlumImuject; Pierce, Rockford, IL) in a total volume of 100 µl on days 1 and 14. Mice were challenged (20 min) via the airways with OVA (1% in saline) (endotoxin concentration, 0.307 ELISA units (EU)/mg protein; BioWhittaker, Walkersville, MD) for 3 days (days 28, 29, and 30; primary challenge) using ultrasonic nebulization (AeroSonic ultrasonic nebulizer; DeVilbiss, Somerset, PA). Control mice groups received OVA challenge alone. For the secondary challenge protocol, 6 wk after the primary challenge, mice were exposed to a single OVA challenge (1% in saline; secondary challenge), and airway reactivity and tissues were assessed 48 h later (30). To assess EPR and LPR, 6 wk after the primary challenge mice were exposed to OVA (5% in saline) (endotoxin concentration, 0.342 EU/mg protein) for 20 min (29).
Administration of the soluble IL-13R2-IgGFc fusion protein
(sIL-13R2-Fc)
Murine IL-13R2-human IgG (hIgG) fusion protein was
prepared as previously described (26). In the secondary
challenge protocol, IL-13R2-hIgG fusion protein was administered by
i.p. injection (300 µg/mouse) 24 h and 1 h before and
24 h after the secondary challenge. In the EPR and LPR study,
IL-13R2-hIgG fusion protein (300 µg/mouse) was administered
24 h and 1 h before the 5% OVA challenge. As a control, a
human IgG (control AB) was administered to one group of animals in the
same fashion.
Determination of Airway Function
To assess airway function following secondary challenge, airway responsiveness was assessed as a change in airway function after challenge with aerosolized metacholine (MCh) administered for 10 s (60 breaths/min, 500-µl tidal volume) in increasing concentrations (1.5625, 3.125, 6.25, and 12.5 mg/ml). Anesthetized (pentobarbital sodium, i.p., 70–90 mg/kg), tracheostomized (18G cannula) mice were mechanically ventilated (160 breaths/min, tidal volume to 150 µl, positive end-expiratory pressure of 2–4 cm H2O) and lung function was assessed using methods described by Takeda et al. (31). RL and Cdyn were continuously computed (Labview; National Instruments, Dallas, TX) by fitting flow, volume, and pressure to an equation of motion. Maximum values of RL and minimum levels of Cdyn were taken and expressed as a percentage change from baseline following PBS aerosol.
To monitor EPR and LPR, airway responsiveness was assessed using single-chamber whole-body plethysmography (Buxco Electronics, Sharon, CT) as described previously (29) following changes in enhanced pause (Penh). When responsiveness to the allergen challenge was evaluated, animals were placed in the plethysmograph and baseline values were recorded. At each measurement of airway function, recordings were monitored for 3 min and Penh values measured during this sequence were then averaged. To determine nonspecific responsiveness, Penh was monitored after mice were exposed to nebulized saline for 3 min. All further responses were compared with the Penh values measured after saline inhalation, which was taken as 1. Then animals were provoked with OVA (5% in saline) for 20 min and airway responsiveness was measured at 5, 15, 30, 45, and 60 min and then every 30 min for the ensuing 8 h. The results of EPR are shown in real time. For LPR, the highest increase in Penh was considered as the maximum and values recorded 2.5 h before and after the maximal response are shown (29).
Bronchoalveolar lavage
Immediately after assessment of AHR, lungs were lavaged via the tracheal tube with HBSS (1 x 1 ml, 37°C). Total leukocyte numbers were measured (Coulter Counter; Coulter, Hialeah, FL). Differential cell counts were performed by counting at least 300 cells on cytocentrifuged preparations (Cytospin 2; Cytospin, Runcorn, Cheshire, U.K.), stained with Leukostat (Fisher Diagnostics) and differentiated by standard hematological procedures.
Histochemistry
Lungs were fixed by inflation (1 ml) and immersion in 10% formalin. Cells containing eosinophilic major basic protein (MBP) were identified by immunohistochemical staining as previously described using rabbit-anti mouse MBP (kindly provided by Dr. J. J. Lee, Mayo Clinic, Scottsdale, AZ) (32). The slides were examined in a blinded fashion with a Nikon microscope (Melville, NY) equipped with a fluorescein filter system. Numbers of peribronchial eosinophils in the tissues were evaluated using IPLab2 software (Signal Analytics, Vienna, VA) for the Macintosh counting 6–8 different fields per animal.
For detection of mucus-containing cells in formalin-fixed airway tissue, sections were stained with periodic acid Schiff (PAS), H&E, and quantitated as previously described (32).
Measurement of cytokines
Cytokine levels in the BAL fluid were measured by ELISA as
previously described (32). IFN-
, IL-4, IL-5, IL-10,
IL-12 (BD PharMingen, San Diego, CA) and IL-13 (R&D Systems,
Minneapolis, MN) ELISAs were performed according to the manufacturer’s
directions. The limits of detection were 4 pg/ml for IL-4, IL-5, and
IL-13 and 10 pg/ml for IL-10, IL-12, and IFN-.
Measurement of total and OVA-specific Antibody
Serum levels of total IgE and OVA-specific IgE, IgG1, and IgG2a were measured by ELISA as previously described (32). Briefly, 96-well plates (Immulon 2; Dynatech, Chantilly, VA) were coated with either OVA (5 µg/ml) or purified anti-IgE (02111D; BD PharMingen). After addition of serum samples, a biotinylated anti-IgE Ab (02122D; BD PharMingen) was used as detecting Ab, and the reaction was amplified with avidin-HRP (Sigma-Aldrich). IgG2a was detected using alkaline phosphatase-labeled anti-IgG2a (02013 E; BD PharMingen). The OVA-specific Ab titers of the samples were related to pooled standards that were generated in the laboratory and expressed as EU per milliliter. Total IgE levels were calculated by comparison with known mouse IgE standards (BD PharMingen). The limit of detection was 100 pg/ml for total IgE.
Statistical analysis
ANOVA was used to determine the levels of difference between all groups. Comparisons for all pairs were performed by Tukey-Kramer honest significant difference test. Values of p for significance was set to 0.05. Values for all measurements were expressed as the mean ± SEM.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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To determine whether IL-13 is released after allergen challenge in
the lungs of mice with already established airway disease, levels of
IL-13 were assessed in BAL fluid. Eight hours after the 5% OVA
challenge in previously sensitized and challenged mice, levels of IL-13
were significantly (p < 0.001) increased in
BAL fluid compared to nonsensitized control mice (Fig. 1
A). In addition, 48 h
after the secondary 1% OVA challenge in previously sensitized and
challenged mice, levels of IL-13 in BAL fluid were significantly
(p < 0.001) higher compared to the
nonsensitized control mice (Fig. 1B). Treatment with
sIL-13R2-Fc significantly (p < 0.001)
reduced levels of IL-13 measured in BAL fluid 8 and 48 h after the
individual challenges (Fig. 1).
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2-Fc inhibits the development of LPR following allergen
challenge
After exposure to 5% OVA, sensitized and challenged mice
developed both an EPR and a LPR. Relative increases in Penh reached a
maximum at 15 min after the OVA challenge and returned to baseline 60
min after the challenge (Fig. 2). This
early increase in Penh was only seen in mice which were previously
sensitized and challenged and not in nonsensitized mice. Sensitized and
challenged mice treated with sIL-13R2-Fc showed the same early Penh
increase as the mice treated with the control Ab (Fig. 2). Mice
previously sensitized and challenged to OVA and treated with the
control Ab developed LPR (Fig. 2). In contrast, sensitized and
challenged mice treated with sIL-13R2-Fc did not develop a LPR
response (Fig. 2).
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2-Fc does not affect inflammatory changes during the
LPR
In previous studies, the development of an LPR has been associated
with inflammatory changes in lung tissue (29). To
determine if neutralization of IL-13 affects inflammatory changes in
the lung, we assessed tissue inflammation 8 h after the 5% OVA
challenge. Lung tissue was stained with H&E, PAS, and anti-MBP.
H&E-stained slides showed a slight increase in peribronchial
inflammation in sensitized and challenged animals (Fig. 3C) compared to the
nonsensitized animals (Fig. 3A). Mice treated with
sIL-13R2-Fc demonstrated similar increases in tissue inflammation
(Fig. 3E). MBP staining of lung tissue revealed a
significant (p < 0.01) increase of eosinophils
in peribronchial lung tissue in sensitized and challenged mice treated
with the control Ab (mean ± SEM: 43 ± 7 eosinophils/mm
basement membrane (BM)) or sIL-13R2-Fc (36 ± 5 eosinophils/mm
BM) (Fig. 4C), compared to the
nonsentitized mice (1 ± 0 eosinophils/mm BM) (Fig. 4A).
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B), whereas sensitized and challenged mice treated with
control Ab showed goblet cell hyperplasia (67.4 ± 11.7
PAS-positive cells/mm BM) (Fig. 3D). Few PAS-positive cells
were detected in mice treated with the sIL-13R2-Fc (4.2 ± 2.8
PAS-positive cells/mm BM) (Fig. 3F).
sIL-13R2-Fc inhibits the development of AHR in established
airway disease
To evaluate the effect of sIL-13R2-Fc on the development of
nonspecific AHR to inhaled MCh in fully allergic mice, we waited 6 wk
after the primary challenge and then rechallenged the animals. We have
previously shown that at this time point, the inflammatory reaction and
AHR developing after primary challenge are resolved but that a
secondary airway challenge induces a strong inflammatory reaction with
development of AHR (30). Indeed, previous sensitized and
challenged mice showed an increase in RL and a decrease in Cdyn to MCh
(Fig. 5) 48 h after the secondary
challenge. Under these conditions, sIL-13R2-Fc treatment inhibited
both the increases in RL and decreases in Cdyn (Fig. 5). Baseline RL
and Cdyn were not affected by allergen or sIL-13R2-Fc treatment
(data not shown).
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2-Fc decreases airway inflammation after secondary
challenge
In sensitized mice, inflammatory cell recruitment into the airways
was increased after secondary airway challenge (Fig. 6). Increased total cell numbers was
largely due to increased numbers of eosinophils. There was also a small
but significant (p < 0.05) increase in the
number of lymphocytes and neutrophils compared to the challenged only
mice (Fig. 6). Administration of sIL-13R2-Fc at the time of the
secondary challenge led to a significant (p <
0.05) decrease in total cell numbers as well as in eosinophil numbers
(Fig. 6).
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2-Fc on tissue inflammation and goblet cell
hyperplasia
Lung tissue was obtained and processed 48 h after the
secondary allergen provocation. Increased peribronchial and
perivascular inflammatory infiltrates were seen in sensitized and
challenged mice treated with the control Ab (Fig. 3G). Mice
treated with sIL-13R2-Fc still demonstrated an inflammatory
infiltrate, albeit reduced overall (Fig. 3I). To
specifically quantitate the infiltration of eosinophils, tissue
sections, were stained with anti-MBP Ab. After the secondary
challenge, sensitized and challenged mice treated with the control Ab
(Fig. 4E) demonstrated a significant increase in
peribronchial MBP-positive cells compared to control mice (Fig. 4D) (means ± SEM; 89 ± 5 eosinophils/mm BM in
mice treated with the control Ab compared to 3 ± 0 in challenged
only mice p < 0.001). The number of peribronchial
MBP-positive cells after the secondary challenge was significantly
lower in sIL-13R2-Fc-treated mice (Fig. 4F) (55 ± 7
eosinophils/mm BM), but were still significantly higher when compared
to challenged only mice (p < 0.01,
respectively).
To assess the degree of goblet cell hyperplasia, tissue sections were
stained with PAS. After secondary challenge, challenged only mice
showed no PAS-positive cells (mean ± SEM: 0 ± 0
PAS-positive cells/mm BM, whereas sensitized and challenged mice
treated with control Ab showed many PAS-positive cells (122.7 ±
4.7 PAS-positive cells/mm BM) (Fig. 3H). In contrast,
sensitized and challenged mice treated with sIL-13R2-Fc showed only
scattered PAS-positive cells (10.5 ± 5.9 PAS-positive cells/mm
BM) (Fig. 3K).
Effect of sIL-13R2-Fc on cytokine production following secondary
challenges
Forty-eight hours after secondary allergen challenge, BAL fluid
was obtained to assess Th1 (IFN-), pro-Th1 (IL-12), Th2 (IL-4,
IL-5), and anti-inflammatory cytokine (IL-10) levels. After the
secondary challenge, Th1 (IFN-) and pro-Th1 (IL-12) cytokines, as
well as IL-10, were decreased in sensitized and challenged mice treated
with the control Ab compared to challenged-only mice (Fig. 7). IL-5 production was increased in
sensitized and challenged mice treated with control Ab. Treatment with
sIL-13R2-Fc did not significantly affect IFN-, IL-12, or IL-10
production, but significantly inhibited IL-5 production (Fig. 7). IL-4
was not detectable in the BAL fluid of challenged only mice. In
sensitized and challenged mice treated with the control Ab, mean
(±SEM) levels were 38.8 ± 12.1 pg/ml. Levels of IL-4 were lower
in sensitized and challenged mice treated with sIL-13R2-IgG mice
(23.2 ± 2.2 pg/ml) but did not achieve statistical significance
(p = 0.12) compared to the control
Ab-treated mice.
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2-Fc treatment does not modify Ig production
Serum from sensitized and challenged mice treated with control Ab
showed elevated Ig levels compared to nonsensitized control mice
following the secondary challenge protocol (Table I). Treatment with sIL-13R2-Fc did not
significantly alter levels of total IgE, OVA-specific IgE, IgG1, or
IgG2a (Table I).
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Blockade of IL- 13 was achieved following systemic administration of a
soluble fusion protein (slL- 13 R2-Fc) consisting of the
extracellular domain of the murine IL-13 high affinity receptor fused
to the Fc portion of human IgG1; this fusion protein specifically binds
to and neutralizes IL-13 (26) and as demonstrated in the
present study, lowered IL-13 levels in BAL fluid of sensitized and
challenged mice following treatment compared to mice treated with a
control Ab. It has been shown previously that administration of this
fusion protein in OVA-sensitized and challenged A/J mice inhibited the
development of AHR and mucus production, but did not affect airway
inflammation or OVA-specific IgE (7). In a different mouse
strain (BALB/c mice), treatment with the same fusion protein inhibited
AHR, mucus production, and BAL eosinophilia, without any effect on BAL
neutrophilia (4). These results highlight some of the
strain-to-strain differences following a primary challenge protocol. As
a corollary, when administered intranasally, rIL-13 induces AHR, BAL
eosinophilia and neutrophilia, and mucus production
(7).
Previous work from this laboratory, using similar approaches,
demonstrated temporal differences in the up-regulation of IL-4 then
IL-13 production in allergen-induced AHR and inflammation, at least
following a primary, single intranasal challenge with allergen in
sensitized mice (32). As well, we defined differences in
the nature of the inflammatory infiltrate, in the read-out of airway
function monitored and in the response to interventions when primary
and secondary challenge protocols were compared (33).
Given the suggestive potency of IL-13 blockade in effectively
preventing a number of these responses in primary challenge models
(4, 7) and the increased levels of IL-13 in BAL fluid
following secondary challenge, we examined the effects of the IL-13
inhibitor in a secondary exposure model of previously sensitized mice.
Treatment with slL-13R2-Fc decreased, but did not completely
abolish, airway inflammation following secondary challenge. When
compared to control Ab (human IgG) treated mice, numbers of eosinophils
and lymphocytes were decreased about 60% in the BAL fluid.
Nonetheless, despite the presence of residual inflammatory infiltrates
following treatment, AHR was virtually abolished following secondary
challenge. This absence of a direct correlation between BAL and tissue
eosinophilia numbers and AHR is now well-described in many species,
including humans. Although there is a clear-cut relationship between
AHR and eosinophil numbers (perhaps more in tissue than in BAL; Ref.
32) in many studies, a number of exceptions have now been
described. A major deficiency in trying to correlate eosinophil numbers
and airway function is the absence of a reliable marker of eosinophil
activation. The findings in the present study are also similar to
results described in IL-13-deficient mice. After sensitization and
airway challenge, IL-13-deficient mice demonstrate the same degree of
airway inflammation as wild-type mice, but IL-13-deficient mice failed
to develop AHR (6), suggesting that airway inflammation or
at least the accumulation of inflammatory cells in the airways in the
absence of IL-13 is not sufficient for the development of AHR.
This was certainly true in the present study for mice in which
airway disease had already been established. Treatment with
sIL-13R2-Fc completely prevented the development of the LPR and AHR
after secondary challenge, whereas inflammatory changes were only
reduced. These data suggest that IL-13 is critical to the development
of AHR, perhaps beyond the association with numbers of inflammatory
cells, eosinophils, lymphocytes, or neutrophils.
In agreement with previous studies (4, 7), treatment with
sIL-13R2-Fc abolished goblet cell hyperplasia and induced mucus
secretion, probably by direct reduction of MUC-5 gene expression in
epithelial cells (17). These responses are not affected in
IL-5- and eotaxin-deficient mice (which fail to develop airway
eosinophilia), indicating that IL-13-induced mucus secretion is
dissociated from airway eosinophilia (14). This
dissociation of airway inflammation, mucus cell hyperplasia, and
altered airway function has been described (34). In
STAT6-deficient mice, reconstitution of STAT6 only in epithelial cells
was sufficient for IL-13-induced AHR and mucus production in the
absence of inflammation, demonstrating the importance of IL-13 directly
on airway epithelial cells for mucus production and development of
AHR.
IL-13 shares structural characteristics and functional properties with
IL-4. The IL-4R chain is a component of the IL-4 and the IL-13
receptors (12). Signaling through the IL-4R chain
induces STAT6 activation, which is critical for the development of AHR
and airway inflammation (25). Despite these similarities,
IL-4 and IL-13 have differences in their function in allergen-induced
airway disease. IL-4 is critical for Th2 cell induction
(35), especially during the sensitization phase
(20, 21, 22), but it has been shown that in the absence of
IL-4, AHR, lung eosinophilia and mucus production can still be induced
(36). In contrast, IL-13 appears to be critical during the
airway challenge phase, at least for the development of AHR (6, 7). IL-13-deficient mice develop airway inflammation, without
developing AHR, whereas mice lacking both IL-4 and IL-13 neither
develop airway inflammation nor AHR (6). It has been
proposed that IL-4 is required for the persistence of Th2 cells in vivo
(37) and the presence of IL-4 might be more important in
chronic airway disease. In the present study, following the secondary
challenge protocol, sIL-13R2-Fc was effective in preventing the
development of AHR after allergen provocation, without significantly
altering IL-4 levels in BAL fluid. In the same model, neutralization of
IL-4 using a soluble IL-4R (which targets only IL-4 signaling), had
little effect on development of AHR or airway inflammation
(38), implying that IL-13, more than IL-4, is important in
the development of AHR in already established allergic airway
disease.
A direct effect of IL-13 on airway epithelial cells has been proposed with induction of MUC-5 gene expression. IL-13 may also induce neutrophil recruitment (4) and activation (15) in the airways. Interestingly, in allergic airway disease neutrophil recruitment may be directly associated with goblet cell metaplasia as pretreatment with an IL-8-blocking Ab prevented both IL-13-induced neutrophil recruitment and mucin production (15). In the present study, inhibition of IL-13 led to a small reduction of neutrophil numbers in BAL fluid, but whether this neutrophil influx plays a role in the development of AHR remains to be elucidated. Under some conditions, mucus production may not be directly associated with alterations in airway function (24).
In humans, the measurement of early and late phase airway responses
following allergen challenge is often used to assess the effectiveness
of treatment interventions (39, 40). Murine models of
allergic airway disease demonstrate an early and late airway response
to inhaled allergen. Previous studies have shown that the early
response following allergen challenge is dependent on the presence of
allergen-specific IgG (41) and can be abolished using
2-adrenoceptor antagonists or cromoglycates
(29). In the present study, neutralization of IL-13 had no
effect on the early airway response. This is not surprising as
neutralization of IL-13 did not have any effect on serum levels of
allergen-specific Abs. It has been shown that the LPR is associated
with an increase in IL-5 levels in BAL fluid and tissue eosinophilia
and can be suppressed by treatment with either anti-IL-5,
cromoglycates, or hydrocortisone (29). We found increased
levels of IL-13 in BAL fluid at the time of the late airway response
and treatment with the sIL-13R2-Fc completely abolished the
development of the LPR. Interestingly, IL-13 neutralization showed no
effect on tissue eosinophil inflammation at this time point, supporting
the possibility of a direct effect of IL-13 on airway function,
independent of airway inflammation.
Secondary exposure to a single provocative OVA aerosol in sensitized
mice elicited airway changes similar to those obtained after a series
of primary challenges, confirming previous results (30).
We previously showed a differential regulation of AHR in the central
and peripheral airways monitoring these two parameters of airway
function (30, 33). It has been proposed that changes in
dynamic compliance reflect narrowing of peripheral airways, whereas
changes in airway resistance represent airflow obstruction of central
airways (42, 43, 44). In previous studies, we have shown that
eosinophilic inflammation might relate to changes in the central
airways while changes in the epithelium of peripheral airways,
including mucus production, may relate to changes in dynamic compliance
(30, 33). Interestingly, and different from anti-IL-5
and anti-very late Ag-4 treatment, sIL-13R2-Fc is capable
of inhibiting both changes in airway resistance and dynamic compliance,
suggesting an effect on central and peripheral airway function
following secondary challenge.
In summary, our results show that IL-13 is essential to the development of a LPR following airway challenge of mice with established allergic disease. In addition, we demonstrate that blockade of IL-13 can prevent changes in central and peripheral airway physiology following secondary allergen challenge. The data suggest that targeting IL-13 may be important in the treatment of chronic allergic asthma.
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Acknowledgments |
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Footnotes |
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2 C.T. and C.D. contributed equally to this work.
3 Address correspondence and reprint requests to Dr. Erwin W. Gelfand, 1400 Jackson Street, Denver, CO 80206. E-mail address: gelfande{at}njc.org
4 Abbreviations used in this paper: AHR, airway hyperresponsiveness; BAL, bronchoalveolar lavage; EPR, early phase response; LPR, late phase response; RL, lung resistance; Cdyn, dynamic compliance; EU, ELISA unit; sIL-13R2-Fc, soluble IL-132-IgGFc; hIgG, human IgG; MCh, metacholine; Penh, enhanced pause; MBP, major basic protein; PAS, periodic acid Schiff; BM, basement membrane.
Received for publication June 28, 2002. Accepted for publication September 30, 2002.
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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chain in the allergic lung. J. Immunol. 167:1683.2: molecular cloning, characterization, and comparison with murine IL-13 receptor 1. J. Immunol. 161:2317.This article has been cited by other articles:
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 T. Koya, N. Miyahara, K. Takeda, S. Matsubara, H. Matsuda, C. Swasey, A. Balhorn, A. Dakhama, and E. W. Gelfand CD8+ T Cell-Mediated Airway Hyperresponsiveness and Inflammation Is Dependent on CD4+IL-4+ T Cells J. Immunol., September 1, 2007; 179(5): 2787 - 2796. [Abstract] [Full Text] [PDF]
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T. Kallinich, K. C. Beier, U. Wahn, P. Stock, and E. Hamelmann T-cell co-stimulatory molecules: their role in allergic immune reactions Eur. Respir. J., June 1, 2007; 29(6): 1246 - 1255. [Abstract] [Full Text] [PDF]
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D. C. Webb, Y. Cai, K. I. Matthaei, and P. S. Foster Comparative Roles of IL-4, IL-13, and IL-4R{alpha} in Dendritic Cell Maturation and CD4+ Th2 Cell Function J. Immunol., January 1, 2007; 178(1): 219 - 227. [Abstract] [Full Text] [PDF]
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Y. Tabata, W. Chen, M. R. Warrier, A. M. Gibson, M. O. Daines, and G. K. K. Hershey Allergy-Driven Alternative Splicing of IL-13 Receptor {alpha}2 Yields Distinct Membrane and Soluble Forms J. Immunol., December 1, 2006; 177(11): 7905 - 7912. [Abstract] [Full Text] [PDF]
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