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Departments of
*
Physiology and
Comparative Medicine, East Carolina University School of Medicine, Greenville, NC 27858;
Department of Biology, Southern Adventist University, Collegedale, TN 37315; and
§
Myrvik Enterprises, Southport, NC 28461
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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. These cytokines lead
to the production of IFN-
by NK cells. To determine whether chitin
could down-regulate Th2 responses, chitin was given orally (8 mg/day
for 3 days before and 13 days during ragweed allergen immunization) in
BALB/c and C57BL/6 mice. These ragweed-immunized mice were given
ragweed intratracheally on day 11. Three days after the challenge, the
immunized mice with saline (controls) showed increases in serum IgE
levels and lung eosinophil numbers. The chitin treatment resulted in
decreases of these events in both strains. To dissect the inhibitory
mechanisms of Th2 responses, spleen cells (4 x 106
cells/ml) isolated from the ragweed-immunized mice (controls) were
cultured in the presence of ragweed and/or chitin for 3 days (recall
responses). Ragweed alone stimulated the production of IL-4 (0.6
ng/ml), IL-5 (20 U/ml), and IL-10 (3.2 ng/ml), but not IFN-.
Ragweed/chitin stimulation resulted in significant decreases of IL-4,
IL-5, and IL-10 levels and the production of IFN- (48 U/ml).
Moreover, spleen cells isolated from the chitin-treated mice showed
ragweed-stimulated IFN- production (15 U/ml) and significantly lower
levels of the Th2 cytokines, suggesting that the immune responses were
redirected toward a Th1 response. Collectively, these results indicate
that chitin-induced innate immune responses down-regulate
Th2-facilitated IgE production and lung eosinophilia in the allergic
mouse. |
Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Inflammation in allergic asthma is generated and activated by
endogenous proinflammatory cytokines produced by Th2-type lymphocytes:
IL-4 facilitates IgE production and humoral immunity; IL-5 facilitates
replication and activation of eosinophils. These allergen-induced Th2
responses enhance airway hyperreactivity in mouse models, although the
mechanism(s) appears to be multifactorial depending on mouse strains
(3, 4, 5). In contrast, the development of Th1/cell-mediated
immunity responses induced by intracellular bacterial infection is
characterized by the initial production of IL-12, TNF-, and IL-18 by
macrophages (M
)3
phagocytosing bacteria. These M cytokines subsequently induce
IFN- production by NK cells and Th1 lymphocytes. It is of importance
that Th1 cytokines reverse Th2 cell-facilitating allergic inflammation.
Particularly, the administration of exogenous IFN- or IL-12 appears
to inhibit such IL-4/IL-5-associated allergic asthma responses in
patients and allergic animal models (6, 7, 8).
Recently, we have studied the mechanisms of innate immunity induced by
heat-killed (HK) Mycobacterium bovis BCG or
Propionibacterium parvum. We have found that when M
phagocytose bacteria or their products through the M mannose
receptors, they initiate production of IL-12, IL-18, and TNF-, all
of which are extracellular signaling cytokines for IFN- production
(9, 10, 11). To imitate this response, we have created
nonantigenic mimetic microbes consisting of 1–10 µm chitin (polymers
of N-acetyl-D-glucosamine) particles,
which are recognized and ingested by M through the mannose receptor
(11). Our previous study (10) clearly
indicated that 1–10 µm chitin particles, but not soluble chitin or
nonphagocytosable size particles (>50 µm), induce the production of
Th1 cytokines including IFN- in vitro and in vivo in mouse models.
The capacity to induce Th1 cytokines by chitin is comparable with that
induced by HK-BCG or HK-Propionibacterium acnes suspensions
(9, 11). In contrast, other phagocytosable particles, such
as chitosan, ß-glucan, latex beads, IgG-opsonized SRBC, and
complement (C3bi)-opsonized SRBC, do not induce Th1 cytokines
(11, 12).
To evaluate the potential for chitin to down-regulate allergic inflammation in vivo, we utilized a mouse model of allergic airway inflammation elicited by ragweed allergen clinically relevant to human asthma (6). Chitin preparations were given orally. In this study, we present the results of the chitin treatment as an attractive therapy for IgE-mediated (allergic) diseases.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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BALB/c and C57BL/6 female mice (6–7 wk old) were obtained from Harlan Laboratory (Indianapolis, IN) and The Jackson Laboratory (Bar Harbor, ME), respectively, maintained in barrier-filtered cages, and fed Purina Laboratory Chow and tap water ad libitum.
Chitin particle preparation
Chitin particles (1–10 µm diameter) were prepared from purified chitin powders (Sigma, St. Louis, MO), as described previously (10, 13), suspended in saline (10–16 mg/ml), autoclaved, and stored at 4°C until use. The chitin preparations contained undetectable levels of endotoxin (<0.03 EU/ml), as determined by the Limulus amebocyte lysate assay (Sigma).
Immunization of mice with ragweed
Mice were sensitized with ragweed allergen, as described
previously (6). The schedule of the sensitization is shown
in Table I
. Briefly, mice were immunized
with two i.p. injections of endotoxin-free ragweed allergen (<0.03
EU/ml; Geer Laboratories, Lenoir, NC), 100 µg/dose (5000 protein
nitrogen units/dose) suspended in 1:4 aluminum hydroxide adjuvant
(Imject Alum; Pierce, Rockford, IL) on days 0 and 4. Eleven days after
the initial sensitization, an i.t. challenge was performed with 100
µg of ragweed allergen. Control groups included unimmunized mice
receiving i.t. challenge of 0.1 ml of saline (naive I) or ragweed 100
µg (naive II) on day 11. After 3 days, unless indicated otherwise,
mice were humanely sacrificed, and the blood, spleens, BAL cells, and
lungs were harvested.
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Oral administration of chitin
As shown in Table I
, allergic mice (6–7 mice/group) were given
chitin (5–8 mg/mouse/day) orally on days -3 to 13 (group 1). Chitin
was given 4 h before i.t. challenge of ragweed on day 11. Control
mice received saline (0.5 ml/day) (group 3). In some experiments,
allergic mice received chitin on days 12 and 13 (group 2).
Endotoxin removal
It was noticed that the presence of endotoxin in some allergen
preparations caused neutrophilia (rather than eosinophilia) following
pulmonary allergen challenge in patients with asthma (14).
Endotoxin induces the production of inflammatory mediators including
IL-12, IL-18, and TNF- (9), major targets in this
study. To remove possibly contaminating endotoxin, all soluble
materials including ragweed preparations were passed through 0.22-µm
Zetapor membrane filters (Cuno, Meriden, CT) manufactured for this
purpose (15). The effectiveness of endotoxin removal was
monitored by the Limulus amebocyte lysate assay (Sigma).
Cytokine production in recall responses: spleen cell cultures stimulated with ragweed allergen in the presence or absence of chitin
Spleens were isolated from ragweed-sensitized/challenged mice (3
days after the challenge) and naive I control mice. Spleens in each
group were pooled. Spleen cells (4 x 106
cells/ml) suspended in RPMI 1640 plus 10% heat-inactivated FBS were
incubated with ragweed at 10 µg/ml and/or chitin at 100 µg/ml at
37°C for 3 to 4 days in a CO2 incubator. After
the incubation, the culture supernatants were collected and their
selected cytokine levels (IL-4, IL-5, IL-10, IFN-) were determined
by their respective specific ELISA assays (9).
In some experiments, CD4+ cells and asialo GM1+ NK cells were eliminated with Abs against CD4 (clone GK1.5; American Type Culture Collection, Manassas, VA) and asialo GM1+ (rabbit polyclonal; Accurate Chemical, Westbury, NY), respectively, followed by treatment with guinea pig serum (1:10; Accurate) as a source of complement. The expression of CD4 and DX5 (pan NK cell marker) was determined by indirect immunofluorescence by the staining with anti-CD4 mAb and anti-DX5 mAb (PharMingen, San Diego, CA) in the presence of 5% heat-inactivated newborn calf serum (Life Technologies, Grand Island, NY), pH 7.2, as described previously (9).
To assess regulatory roles of endogenous cytokines (IL-4, IL-10,
IFN-), neutralizing Abs for these cytokines (Endogen, Woburn, MA)
were added to the ragweed-stimulated spleen cell cultures.
Detection of total IgE and ragweed-specific IgE and IgG2a Abs in sera
Ragweed-immunized allergic responses were monitored by measuring
total IgE levels. Blood (5 µl/mouse/interval) was collected from the
tail vein, and serum IgE levels were detected by ELISA using purified
mouse IgE 
isotype (PharMingen) as a standard. Ragweed-specific IgE
and IgG2a levels were measured by ELISA with ragweed Ag-coated 96-well
plates; 5 µg ragweed/0.1 ml/well in 0.1 M sodium acetate buffer, pH
6.5, overnight at 4°C (16). For the detection, alkaline
phosphatase-labeled anti-IgE and anti-IgG2a were used. The
enzyme substrate was p-nitrophenylphosphate: optical
absorbance at 405 nm was read.
Lung histology
Lungs were removed on day 14 and immediately fixed with 10% neutral-buffered Formalin. The fixed lungs were embedded in paraffin, sectioned at a thickness of 4 µm, and stained with hematoxylin and eosin. The slides were evaluated for any abnormalities by a pathologist blinded to the treatment groups. The degree of allergen-induced peribronchial and perivascular inflammation was graded on a subjective scale of 0, 1, 2, 3, and 4 corresponding to severity nomenclature of absent, mild, moderate, marked, or severe, respectively (17).
Statistics
Differences between mean values were analyzed by unpaired Student’s t test. p values less than 0.05, which were calculated as two-tailed p values, were considered statistically significant.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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To assess whether chitin modulates the production of selected Th2
cytokines, spleen cells were isolated from the spleens of
ragweed-sensitized BALB/c mice and incubated with ragweed allergen
and/or chitin. When spleen cells from ragweed-sensitized mice were
rechallenged with ragweed allergen ex vivo (recall responses), they
released significant levels of IL-4, IL-5, and IL-10, but not IFN-
(Fig. 1). Control spleen cells from
unimmunized mice (naive I) did not respond to the allergen. As
previously reported (9), when normal spleen cells were
incubated with chitin alone at 100 µg/ml, they produced IFN- and
IL-10, but not IL-4 or IL-5 (Fig. 1). Chitin also stimulated spleen
cells from ragweed-sensitized mice to produce IFN- and IL-10, but
not IL-4 or IL-5. Finally, when ragweed-sensitized spleen cells were
stimulated simultaneously with ragweed and chitin, the levels of IL-4,
IL-5, and IL-10 produced were significantly reduced compared with those
stimulated by ragweed alone. IFN- levels were also significantly
reduced compared with those stimulated by chitin alone.
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, when CD4
cells were eliminated, ragweed-stimulated IL-4, IL-5, and IL-10
production was significantly impaired, whereas chitin-induced IFN-
production was still intact. In contrast, when asialo
GM1+ NK cells were eliminated, ragweed-induced
IL-4, IL-5, and IL-10 production was intact, but chitin-induced IFN-
production was diminished (Fig. 2). Interestingly, when NK
cell-eliminated spleen cells were stimulated simultaneously by ragweed
and chitin, the down-regulation of IL-4/IL-5/IL-10 production by chitin
was not observed (Fig. 2).
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produced
by NK cells appear to inhibit the Th2 cytokine production. It is
likely, therefore, that the administration of chitin in the allergic
mouse will down-regulate the allergen-induced Th2 immune responses. The prophylactic effects of chitin administration in the allergic BALB/c mouse
Mice immunized with ragweed at the schedule shown in Table I had
been established by Sur et al. (6), and showed high levels
of total serum IgE and lung inflammation including eosinophilia. To
assess whether chitin administration down-regulates these inflammatory
parameters, ragweed-sensitized mice were given chitin orally on days
-3 to 13 (group 1 in Table I).
As shown in Fig. 3A, a
significant elevation of serum IgE levels was observed after day 8. The
levels increased to 4607 ± 1086 ng/ml on day 14. When mice were
treated with chitin, the levels were significantly reduced (2014
± 939 ng/ml, p < 0.0005). Ragweed-specific IgE levels
were also reduced significantly by the chitin treatment, whereas
ragweed-specific IgG2a levels were enhanced by the chitin treatment
(Fig. 3B). The inhibition of total IgE levels was also
observed on days 8, 10, and 12. Less than 50 ng/ml was detected on day
14 in naive I and naive II controls.
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, 3% of lymphocytes, and <2%
neutrophils (data not shown). As shown in Fig. 4, i.t. challenge of ragweed allergen in
ragweed-immunized mice resulted in the migration of lymphocytes,
eosinophils, and neutrophils in BAL fluid. The eosinophil and
lymphocyte levels were reduced significantly by the chitin treatment
(Fig. 4).
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, A (naive II
control), B (saline, group 3), and C (chitin,
group 1), show representative hematoxylin and eosin-stained
peribronchial and perivascular areas of the lungs (x40). Naive animals
had no detectable lung inflammation, whereas the allergic mice treated
with saline (group 3) had significant peribronchial and perivascular
inflammation. Compared with the saline group, the peribronchial, the
perivascular, and total lung inflammation were inhibited in the
chitin-treated group (Table II).
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in the chitin-treated group (group 1) and saline-treated
control (group 3) (data not shown), we monitored IL-4 and IFN-
levels in BAL fluid on day 12 (Fig. 6).
BAL contained IL-4 at 613 pg/ml and IFN- at <5 U/ml in
saline-treated group (group 3). The chitin treatment (group 1) showed
significant inhibition of IL-4 levels (163 pg/ml) and enhancement of
IFN- levels (19.5 U/ml) (Fig. 6). IL-5 and IL-10 levels were not
detected in BAL fluid of these two groups obtained on either day 12 or
14 (data not shown).
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) and showed
no distress or systemic toxicity. The activity of chitin to induce
IL-12, IL-18, TNF-, and IFN- production by normal mouse spleen
cells in vitro was unchanged when chitin was preexposed to 0.1 M
hydrochloric acid (pH 1.8) at 37°C for 4 h (data not shown).
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Since serum IgE levels at the sensitization phase were inhibited
by the prophylactic treatment with chitin (Fig. 3A), we
further determined whether the chitin treatment at the effector phase
of allergic inflammation is still effective. Chitin was given only on
days 12 and 13 (group 2 in Table I) when total serum IgE levels were
relatively high (1000–2800 ng/ml). As shown in Fig. 7, the chitin treatment resulted in
significant decrease of IgE levels on day 14. There were significant
decreases of lymphocyte and eosinophil numbers in BAL on day 14 (Fig. 4). These results suggest that chitin appears to have therapeutic
effects.
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production
Prophylactic treatment with chitin.
To determine whether ragweed allergen-specific Th2 cell functions were
modulated by the prophylactic treatment with chitin (group 1 in Table I), recall responses of spleen cells were conducted. As shown in Fig. 8, ragweed-stimulated IL-4, IL-5, and
IL-10 production was significantly reduced by the chitin treatment,
whereas slight but significant amounts of IFN- were detected. The
production of either IFN- or IL-4/IL-5/IL-10 was not observed when
spleen cells (group 1) were depleted of CD4+
cells by anti-CD4 plus guinea pig serum before the recall responses
(data not shown).
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are known to down-regulate Th1 and Th2
responses, respectively (9, 10, 18, 19, 20). IL-10 also
inhibits allergen-stimulated IL-4 and IL-5 production
(21). To assess regulatory roles of these endogenous
cytokines (IL-4, IL-10, IFN-), neutralizing Abs for these cytokines
at 20 µg/ml were added to the ragweed-stimulated spleen cell
cultures. When rat Ig at 20 µg/ml was added to the cultures as a
control, the cytokine profiles were identical to those untreated (data
not shown). Fig. 8 shows that ragweed-stimulated IL-4/IL-5 production
by spleen cells was significantly enhanced by either anti-IL-10 or
anti-IFN- treatments in the chitin groups, suggesting that
endogenous IL-10 and IFN- inhibit IL-4/IL-5 production.
Ragweed-stimulated IL-4/IL-5/IL-10 production by spleen cells from
chitin-treated mice was also enhanced by anti-IFN- treatments.
However, the treatment with anti-IFN- did not enhance
IL-4/IL-5/IL-10 production in allergic mice given saline (group 3). It
is likely, therefore, that endogenous IFN- produced by spleen cells
from chitin-treated mice inhibits production of these Th2 cytokines.
Finally, the treatment with either anti-IL-4 or anti-IL-10
resulted in significant increases in ragweed-stimulated IFN-
production. It is suggested that the immunized mice generate
ragweed-specific Th1 cells when they were prophylactically treated with
chitin.
Therapeutic treatment with chitin.
Unlike the prophylactic treatment, the therapeutic treatment resulted
in no change of the levels of IL-4, IL-5, and IL-10 in the recall
responses. There was no detectable level of IFN- produced by the
recall responses. Furthermore, the inhibition of endogenous IL-4 or
IL-10 by the Ab treatments did not show the production of IFN- (data
not shown).
The prophylactic effects of chitin administration in the allergic C57BL/6 mouse
To further confirm the effects of chitin, we employed C57BL/6
mice, which are higher responders for cell-mediated immunity/Th1
responses, but lower responders for allergic responses compared with
BALB/c mice. C57BL/6 mice were immunized with ragweed at the identical
schedules (Table I). Serum IgE levels detected on day 14 (801 ±
357 ng/ml) were lower than those in ragweed-immunized BALB/c mice (Fig. 3A). After the treatment with chitin (5 mg/dose) on days -3
to 13, the levels decreased to 330 ± 158 ng/ml
(p < 0.01, data not shown). Eosinophil levels
were comparable with those found in BALB/c mice, and the chitin
treatment resulted in a decrease in eosinophil numbers (Fig. 9).
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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, IFN-) (9, 10, 11). These are cytokines that
are generally seen at early stages of infection (innate immunity)
caused by intracellular bacteria such as M. bovis BCG
(9, 10, 11). Innate immunity is important for protection
against intracellular bacterial infections and to induce acquired
immunity specific for bacteria (22). It is well
established that Th1 cytokines, produced in innate immunity,
down-regulate allergic immune (Th2) responses (18). The
present study of recall responses clearly shows that
allergen-stimulated IL-4, IL-5, and IL-10 production is significantly
inhibited by the presence of chitin in the spleen cell cultures (Fig. 1). Our results suggest that IFN- produced by NK cells, at least in
part, is responsible for the inhibition of the production of these Th2
cytokines.
The provocative findings are that chitin, given orally, down-regulates
allergen-induced IgE production and lung inflammation including
eosinophilia in our ragweed-immunized allergic model. We also found
that an increase in IFN- levels and a reduction of IL-4 levels in
BAL are associated with a reduction of allergen-specific IgE levels and
an increase in allergen-specific IgG2a levels, indicating isotype
switching by B cells. Interestingly, when chitin is given
prophylactically, the chitin-treated mice appear to generate
ragweed-specific Th1 cells, although the Th1 cell generation would
significantly be reduced by endogenous IL-4 and IL-10, which are also
produced during ragweed-stimulated recall responses. Our results
strongly suggest that IFN- produced by these Th1 cells as well as NK
cells down-regulates IL-4-facilitated IgE formation and
IL-5-facilitated eosinophil migration. However, ragweed-specific Th1
cells were not detected when chitin was given only during the effector
phase of allergic inflammation. In this case, IFN- produced by NK
cells would play an important role for the down-regulation of IgE
levels and lung eosinophilia.
Consistent with earlier observations (9, 23), our study
clearly showed that IL-10 is produced by ragweed-stimulated CD4 cells
and chitin-stimulated M and NK cells. In addition, IL-10 is produced
by many other diverse cell populations, including bronchial epithelial
cells and B cells (24, 25). The immunoregulatory roles of
IL-10 for allergic responses appear to be complex. It has been
suggested that IL-10 inhibits innate immunity as well as both Th1 and
Th2 responses to Ags most probably by inhibiting APC (9, 21, 26). In our preliminary studies using IL-10-deficient C57BL/6
(KO) mice, sensitization with endotoxin-free ragweed in KO mice
resulted in significantly higher levels of serum IgE levels and lung
eosinophilia compared with those of allergic wild-type controls. The
increases in serum IgE levels and lung eosinophil numbers in KO mice,
both of which are facilitated by IL-4 and IL-5, respectively, were
closely associated with the inhibitory effects of IL-10 on
allergen-specific IL-4/IL-5 production in the recall responses. Oral
administration of chitin at identical schedules employed in the present
study significantly reduced serum IgE levels and lung eosinophilia in
KO mice (manuscript in preparation). In sharp contrast to the
anti-inflammatory effects, IL-10 may be highly relevant for
proinflammatory responses involving mast cell activation: IL-10
significantly enhances mast cell proliferation, allergen-induced
histamine release, and expression of chymases (27, 28).
Therefore, exact regulatory mechanisms of endogenous IL-10, whose
amounts can be controlled by the chitin treatment, remain to be
elucidated.
Chitin, a polymer of
N-acetyl-D-glucosamine, is an
essential component of fungal cell walls and has been the target of
antifungal drugs (nikkomycin Z, polyoxin D (29, 30)).
Chitin is similar in structure to cellulose and has no mammalian
counterpart. Following cellulose, chitin is the second most abundant
polysaccharide found in nature. It comprises the horny substance in the
exoskeleton of crabs, shrimp, and insects as well as the cell walls of
fungi. Chitosan (deacetylated chitin) is nontoxic, nonallergenic,
biodegradable, and biocompatible, and has been used in the development
of a number of prostheses (artificial skin, contact lens, surgical
sutures) that are widely used in medical and veterinary practice
(31, 32). When chitin particles prepared as described
above, essentially 100%
N-acetyl-D-glucosamine, are
administered to mice, they bind to the M plasma membrane mannose
receptors (33). These receptors serve to mediate the
interiorization of the chitin particles that, eventually, are degraded
by lysozyme and
N-acetyl-ß-D-glucosaminidase that
are present in the M of humans and experimental animals (34, 35). Therefore, chitin preparations of nonmicrobial origin
represent very attractive and highly effective products for the
down-regulation of allergic inflammation. The oral administration for
therapeusis/prophylaxis should most likely be the route of choice for
children who suffer from allergic diseases.
In allergic animal models, the administration of IFN- or IL-12
inhibits Th2-driven inflammation (6, 7, 8). Exogenous IL-12
induces IFN- production, which is the most effective cytokine to
down-regulate Th2 responses (7). The mechanisms for
IFN- production are comprehensive. Recently, an additional
IFN--inducing factor (IL-18) was found to contribute to IFN-
production (36). We have confirmed that chitin induces
M to produce IL-12, IL-18, and TNF-, all of which act
synergistically to induce IFN- production by NK cells
(9). Interestingly, chitin-stimulated M also produce
IL-10, which up-regulates NK cell IFN- production (9).
It is, therefore, reasonable to speculate that amounts of exogenous
IL-12 far greater than physiological ranges are required to induce
effective levels of IFN- production. Excessive doses of IL-12 would
be associated with the toxic side effects (37, 38, 39).
Recently, it has been reported that treatment with live or HK bacteria,
including M. bovis BCG, Mycobacterium vaccae, and
Listeria monocytogenes, results in
down-regulation of Th2 responses in various allergic mouse models
(40, 41, 42). These bacterial suspensions are known to induce
Th1 immune responses. Several bacterial components that induce Th1
cytokines have also been identified. Endotoxin, superantigen exotoxins,
and mycobacterial DNA with CpG motifs are able to induce
IL-12/TNF-/IL-18 by M (43, 44, 45), suggesting
usefulness of these components for the down-regulation of allergic
inflammation (17, 46, 47). However, the toxic side effects
of these components are of great concern (48). In the
present studies, mice given chitin orally showed no visible adverse
effects. Interestingly, their body weight tended to increase slightly
compared with mice receiving saline (Table III).
The activity of chitin to induce Th1 cytokine production in vitro is
found to be relatively stable under acidic conditions, although
deacetylation can occur and deacetylated chitin (chitosan) does not
induce Th1 cytokines (10). We found that the activity is
unchanged after treatment with 0.1 M hydrochloric acid at 37°C for
4 h (data not shown). In addition, it is established that 1–10
µm poly(D-L-lactic-coglycolic acid) particles
and polystyrene particles administered directly into the intestines
following a laparotomy are readily internalized by Peyer’s patch M
cells (49, 50). One would expect, therefore, that a part
of the chitin particles given orally are taken up by M cells and
translocated to the pocket region containing M and other leukocytes.
During chitin mobilization in intraepithelial lymphoid tissues, some
cells would produce Th1 cytokines. However, exact mechanisms of mucosal
immunity in the small intestines stimulated by chitin remain to be
elucidated.
Nonpathogenic and pathogenic facultative intracellular bacteria (for
example, L. monocytogenes and M. tuberculosis)
invade and survive in M, and only highly activated M can kill
these bacteria. Since lifestyles in industrialized countries tend to
create environments that eliminate/reduce bacteria (51),
M activation levels that are promoted by such environments are
substantially diminished. Studies using germfree experimental animals
appear to support this hypothesis (52). Our study suggests
that oral administration of chitin may be a substitute for such
bacterial exposures.
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Acknowledgments |
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Footnotes |
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2 Address correspondence and reprint requests to Dr. Yoshimi Shibata, Department of Physiology, East Carolina University School of Medicine, Greenville, NC 27858. E-mail address:
3 Abbreviations used in this paper: M, macrophage; BAL, bronchoalveolar lavage; BCG, bacillus Calmette-Guérin; HK, heat-killed; i.t., intratracheal; KO, knockout.
Received for publication March 17, 1999. Accepted for publication November 23, 1999.
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M. Salagianni, W. K. Loon, M. J. Thomas, A. Noble, and D. M. Kemeny An Essential Role for IL-18 in CD8 T Cell-Mediated Suppression of IgE Responses J. Immunol., April 15, 2007; 178(8): 4771 - 4778. [Abstract] [Full Text] [PDF]
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 S. Sakai, H. Akiyama, Y. Sato, Y. Yoshioka, R. J. Linhardt, Y. Goda, T. Maitani, and T. Toida Chondroitin Sulfate Intake Inhibits the IgE-mediated Allergic Response by Down-regulating Th2 Responses in Mice J. Biol. Chem., July 21, 2006; 281(29): 19872 - 19880. [Abstract] [Full Text] [PDF]
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 S. Bierbaum, R. Nickel, A. Koch, S. Lau, K. A. Deichmann, U. Wahn, A. Superti-Furga, and A. Heinzmann Polymorphisms and Haplotypes of Acid Mammalian Chitinase Are Associated with Bronchial Asthma Am. J. Respir. Crit. Care Med., December 15, 2005; 172(12): 1505 - 1509. [Abstract] [Full Text] [PDF]
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 M. Wills-Karp and C. L. Karp Chitin Checking -- Novel Insights into Asthma N. Engl. J. Med., September 30, 2004; 351(14): 1455 - 1457. [Full Text] [PDF]
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 Z. Zhu, T. Zheng, R. J. Homer, Y.-K. Kim, N. Y. Chen, L. Cohn, Q. Hamid, and J. A. Elias Acidic Mammalian Chitinase in Asthmatic Th2 Inflammation and IL-13 Pathway Activation Science, June 11, 2004; 304(5677): 1678 - 1682. [Abstract] [Full Text] [PDF]
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 Y. Shibata, I. Honda, J. P. Justice, M. R. Van Scott, R. M. Nakamura, and Q. N. Myrvik Th1 Adjuvant N-Acetyl-D-Glucosamine Polymer Up-Regulates Th1 Immunity but Down-Regulates Th2 Immunity against a Mycobacterial Protein (MPB-59) in Interleukin-10-Knockout and Wild-Type Mice Infect. Immun., October 1, 2001; 69(10): 6123 - 6130. [Abstract] [Full Text] [PDF]
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 J. P. Justice, Y. Shibata, S. Sur, J. Mustafa, M. Fan, and M. R. Van Scott IL-10 gene knockout attenuates allergen-induced airway hyperresponsiveness in C57BL/6 mice Am J Physiol Lung Cell Mol Physiol, February 1, 2001; 280(2): L363 - L368. [Abstract] [Full Text] [PDF]
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and 
, Naive control and ragweed-immunized mice,
respectively. *, p < 0.05, and #,
p < 0.0005 compared with the cytokine levels
induced by ragweed (RW) alone and chitin alone, respectively. The data
shown are representative of three independent experiments.
), and were resuspended in
RPMI 1640 plus 10% FBS at 4 x 106 cells/ml. The
remaining procedures of the recall responses were identical to those
described in Fig. 1
