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Laboratory of Host Defense and Germfree Life, Research Institute for Disease Mechanism and Control, Nagoya University School of Medicine, Nagoya, Japan and
Department of Otorhinolaryngology, Shimane Medical University, Izumo, Japan
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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R on mast cells lining
the bronchial surface, which consequently release stored mediators by
granule exocytosis and synthesize leukotrienes and cytokines. The
allergic reaction is further promoted by the recruitment of Th2 cells,
eosinophils, and basophils in the airway. Th1 cells, into which naive
CD4+ T cells differentiate in the presence of
IL-12 and IFN-
, secrete IL-2, IFN-, and TNF-
not only for
induction of cell-mediated immunity but also for inhibition of Th2
responses (5, 6, 7). Therefore, cytokines involved in
Th1-biased response are thought to regulate Th2-mediated allergic
responses. However, the basic mechanisms controlling Th2 responses in
airway allergic responses are not clear. IL-15 is a pleiotropic cytokine that promotes activation, proliferation, and cytokine release of various subsets of T cells (8, 9, 10, 11, 12), NK cells (13), mast cells (14), and B cells (15). With regard to Th1/Th2 cells, IL-15 is reported to be synergistic with IL-12 to induce proliferation of murine Th1 clones (16), whereas it induces IL-5 production by allergen-specific human Th2 clones (17). Thus, IL-15 may influence both Th1 and Th2 cells. Aberrant IL-15 expression was observed in patients with inflammatory autoimmune disease, such as rheumatoid arthritis (18, 19) and inflammatory bowel diseases (20, 21), suggesting that IL-15 is involved in the pathogenesis of inflammatory disease. However, the potential role of IL-15 in allergic responses in vivo remains to be elucidated.
We have recently constructed transgenic (Tg)3 mice expressing IL-15 cDNA encoding a secretable isoform of IL-15 precursor protein under the control of an MHC class I promoter, and we found that the overexpression of IL-15 augmented the in vivo Th1 response to infection with Salmonella choleraesuis, an intracellular bacterium (22). In the present study, we investigated the in vivo roles of IL-15 in allergic responses in a murine model of asthma using IL-15-Tg mice. We found that the pulmonary eosinophilia and Th2 cytokine production in the airway were severely attenuated in OVA-sensitized IL-15-Tg mice following a challenge with inhalation of OVA. IL-15-Tg mice developed Tc1 responses mediated due to the action of CD8+ T cells against OVA, and in vivo depletion of CD8+ T cells by anti-CD8 mAb aggravated the airway allergic inflammation in the IL-15-Tg mice. Adoptive transfer of CD8+ T cells from OVA-sensitized IL-15-Tg mice revealed that the Tc1 cells suppressed Th2 response at induction phase. These results suggest that overexpression of IL-15 in vivo suppresses Th2-mediated allergic airway response via up-regulation of Tc1 responses.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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IL-15-Tg mice, which were constructed using originally described
IL-15 cDNA under the control of an MHC class I promoter, have been
described previously (22). In brief, full-length cDNA
encoding the murine IL-15 gene with the originally described exon 5
(710 bp; Ref. 23) was cloned between the BamHI
and SalI sites of a Tg expression vector, pHSE-3', which
contains the H2-K promoter and Ig enhancer, and 
-globin splice site
and poly(A) signal. Transgene DNAs were microinjected into the male
pronucleus of fertilized single-cell embryos of C57BL/6 mice.
Microinjected eggs were transferred to pseudopregnant C57BL/6 foster
mothers. IL-15-Tg mice were identified by digesting genomic DNA with
PstI followed by Southern blot analysis using an
IL-15-specific probe. Mice were maintained under specific pathogen-free
conditions and offered food and water ad libitum. Age- and sex-matched
C57BL/6 mice obtained from Japan SLC (Hamamatsu, Japan) were used as
control mice. All mice were used at 6–8 wk of age.
Immunization and challenge
Mice were i.p. immunized with 100 µg chicken OVA (Grade IV;
Sigma, St. Louis, MO) absorbed in 100 µl CFA on day 0. Seven days
later, the mice were i.p. injected with 100 µg OVA in 100 µl IFA.
The mice were then exposed to aerosolized PBS or OVA for 30 min/day on
days 14, 16, 18, and 20. The aerosols were introduced into the chamber
using a nebulizer. The concentration of OVA in the nebulizer was 1%
w/v. The immunization protocol is shown in Fig. 1
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Mice were i.p. injected with 400 µg of anti-CD8 mAb 2 days before an initial immunization of OVA/CFA and on day 5 after the immunization. Control mice were i.p. injected with the same dose (400 µg) of rat IgG as an isotype control in the same schedule. The efficacy of CD8+ T cell depletion was monitored by flow cytometric analysis of spleen and bronchoalveolar lavage fluid (BALF) cells.
Adoptive transfer assays
Spleen cells of IL-15-Tg or non-Tg mice, which were sensitized twice with OVA/CFA and OVA/IFA at 7-day intervals, were recovered 14 days after the last sensitization and passed through nylon-wool columns. A CD8+ T cell subset was purified using a MACS column (Miltenyi Biotec, Auburn, CA). The purity of CD8+ T cell subset was confirmed to be more than 98% by FACS analysis. CD8+ T cells (1 x 107 cells) were adoptively transferred into normal mice or mice that had been sensitized with OVA/CFA on day -14 and OVA/IFA on day -7. At 24 h after the adoptive transfer, the normal recipient mice were sensitized with OVA/CFA and OVA/IFA at 7-day intervals. In some experiments, 1 x 107 nylon-wool column-passed T cells from normal mice sensitized with OVA/IFA and OVA/CFA were adoptively transferred into naive IL-15-Tg and non-Tg mice via tail vein inoculation. After 24 h, the mice were then exposed to aerosolized OVA every 2 days for 7 days.
In some experiments, 1 x 107 nylon-wool column-passed T cells from non-Tg mice sensitized with OVA/IFA and OVA/CFA were adoptively transferred into naive IL-15-Tg and non-Tg mice via tail vein inoculation. After 24 h, the mice were then exposed daily to aerosolized OVA for 7 days.
Measurement of OVA-specific IgE, IgG1, and IgG2a
Levels of OVA-specific IgE, IgG1, and IgG2a were determined by ELISA. Sample wells of an ELISA plate were coated with OVA overnight and then blocked with 1% BSA in borate-buffered saline (0.05 M borate, 0.15 M NaCl, pH 8.6, 100 µl/well) at 37°C for 30 min. Diluted samples (100 µl/well) were incubated for 90 min at room temperature (Samples for IgE were diluted 1:100; IgG1, 1:1000; and IgG2a, 1:5). The plates were washed with borate-buffered saline with 0.05% Tween 20 and incubated with peroxidase-conjugated anti-mouse IgE, IgG1, or IgG2a (Nordic Immunology, Minneapolis, MN) for 90 min at room temperature. After further washing, plates were incubated for 20 min at room temperature with 100 µl/well of o-phenylendiamine solution (1 µg/ml with 3% H2O2) and were read for OD at 492 nm.
Analysis of cytokines in BALF and serum
To obtain BALF, mice were anesthetized, a tracheal cannula was
inserted via a midcervical incision, and the airways were lavaged three
times with 1 ml PBS. BALF was immediately centrifuged (10 min, 4°C,
160 x g), and the supernatant was rapidly frozen.
Commercial ELISA kits were used to measure the levels of IL-4 and
IFN- (Genzyme, Cambridge, MA), IL-5 (Techne, AN'ALYZA immunoassay
system; Genzyme), and IL-13 (Quantikine M; R&D Systems Europe,
Abingdon, U.K.) in the BALF. ELISA for mouse IL-15 in the BALF and
serum was performed in triplicate using purified anti-mouse IL-15
mAb (capture mAb, G277-3588; PharMingen, San Diego, CA),
biotin-conjugated anti-mouse IL-15 mAb (second mAb, G277-3960;
PharMingen), and peroxidase-conjugated streptavidin (detection reagent;
Genzyme) as described previously (22).
Staining of BALF cells
BALF cells were stained by the Pappenheim staining method using modified May-Gruenwald’s solution (Merck, West Point, PA) and Giemsa’s stain solution (Katayama Chemical, Osaka, Japan), and the cells were identified as eosinophils, neutrophils, macrophages, and lymphocytes by standard morphology. At least 100 cells were counted, and the absolute number of each cell type was calculated.
Abs and reagents
PE-conjugated anti-CD8 (53-6.7), and FITC-conjugated anti-CD44 (IM7) and anti-CD3 (145-2C11) mAbs were purchased from PharMingen. Cy-Chrome-conjugated anti-CD4 (GK1.5) mAb and Cy-Chrome-conjugated streptavidin were obtained from PharMingen. Anti-H-2Kb/Db (28-8-6, mouse IgG2a) mAb was purchased from PharMingen.
Flow cytometric analysis
The cells were stained with PE-, FITC-, and biotin-conjugated mAbs. To block FcR-mediated binding of the mAb, 2.4G2 (anti-FcR mAb) was added. All incubation steps were performed at 4°C for 30 min. To detect biotin-conjugated mAb, the cells were stained with Cy-Chrome-conjugated streptavidin after incubation with a primary mAb. The stained cells were analyzed by a FACScalibur flow cytometer (Becton Dickinson, Mountain View, CA). Lymphocytes were gated by forward and side scattering.
Osmotic loading of Ag to APCs
Osmotic loading of OVA to APC was conducted as described previously (24). Briefly, OVA was dissolved in serum-free sterile PBS and mixed with a cationic lipid transfection reagent (Roche, Gipf-Oberfrick, Switzerland), N-[1-(-2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium methyl-sulfate (OVA-DOTAP), to a final concentration of 200 µg/ml in a total volume 1 ml for 20 min at room temperature. Casein (casein enzymatic hydrolysate; Sigma) was used as control Ag (CASEIN-DOTAP). This mixture was then added to naive syngeneic splenocytes in RPMI 1640 medium at a concentration of 1 x 105 cells/ml in a total volume of 30 ml and incubated overnight at 37°C in 5% CO2. OVA-pulsed splenocytes were then removed and washed twice in PBS before mytomycin C (MMC)-treatment. After MMC-treatment for 30 min, the splenocytes were suspended in RPMI 1640 medium to a concentration of 2 x 106 cells/ml, and used as APC.
Measurement of cytokine production of spleen cells
Spleen cells were incubated on a nylon-wool column at 37°C in
5% CO2 for 60 min. The cell population eluted
from the column contained >90% T cells, as determined by FACS
analysis with anti-CD3 mAb. A CD4+ T cell or
CD8+ T cell subset was purified from splenic T
cells using MACS (Miltenyi Biotec). The purify of T cell subsets was
confirmed to be more than 98% by FACS analysis. T cells (5 x
105) and MMC-treated naive splenocytes (5 x
105) were cultured in 96-well cell culture plates
(Falcon; Becton Dickinson) with 200 µg OVA. In some experiments,
CD8+ T cells (5 x 105
cells) were cultured in flat-bottom microtiter plates for 2 days with
5 x 105 cells of OVA-DOTAP-treated or
CASEIN-DOTAP-treated APC. To confirm whether CD8+
T cells recognize MHC class I with Ag loading osmotically,
CD8+ T cells of IL-15-Tg mice were placed in
culture with anti-mouse MHC class I mAb (anti-mouse
H-2Kb/Db mAb; 10 µg/ml)
or the same amount of mouse IgG as an isotype control. After 48 h
of culture, the cultured supernatants were collected and the amounts of
secreted IL-4 and IFN- in the supernatants were determined by ELISA.
For cellular proliferation, the cultures were pulsed with 1 µCi/well
[3H]TdR for an additional 6 h after
48 h of culture. [3H]TdR incorporation was
determined by liquid scintillation counting.
Statistical analysis
The statistical significance of the data was determined by Student’s t test. A value of p < 0.05 was taken as significant.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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The IL-15-Tg mice were i.p. sensitized with OVA/CFA followed by
OVA/IFA 7 days later and then exposed to aerosolized OVA or PBS every 2
days from day 14 to day 20 after sensitization (Fig. 1
A). The BALF was recovered
24 h after the last inhalation. As shown in Fig. 1B,
the numbers of total cells and eosinophils in the BALF were markedly
increased in OVA-sensitized mice after OVA inhalation, while the
numbers were significantly lower in OVA-sensitized IL-15-Tg mice after
OVA inhalation (p < 0.05). We next examined
cytokine production in BALF after a challenge with OVA inhalation. We
previously reported that a significant IL-15 level was detected in the
serum of naive IL-15-Tg mice (22). An appreciable level of
IL-15 protein was also detected in BALF even in naive IL-15-Tg mice
(data not shown). As shown in Fig. 1C, a marginal level of
IL-15 was detected in OVA-sensitized non-Tg mice after OVA inhalation,
while a significant level of IL-15 was detected in OVA-sensitized
IL-15-Tg mice irrespective of PBS or OVA inhalation. The levels of IL-5
and IL-13 were increased in the BALF of OVA-sensitized non-Tg mice
after OVA inhalation. In contrast, the increases in IL-5 or IL-13 were
only marginal, if any, in OVA-sensitized IL-15-Tg mice after OVA
inhalation. IL-4 and IFN- levels in the BALF remained at
undetectable levels after OVA inhalation in both groups of mice
sensitized with OVA (data not shown). These results suggest that
OVA-induced airway inflammation is severely impaired in OVA-sensitized
IL-15-Tg mice.
Impaired IgE production in IL-15-Tg mice
To determine which type of T cell responses preferentially
developed in IL-15-Tg mice by OVA sensitization, we first assessed
OVA-specific IgE/IgG2a production in the serum on
day 14 after i.p. injections with OVA/CFA on day 0 and with OVA/IFA on
day 7. The non-Tg mice had the higher OVA-specific IgE level in the
serum than did IL-15-Tg mice after OVA sensitization (Fig. 2; p < 0.05). On the
contrary, the level of OVA-specific IgG2a was
significantly higher in the IL-15-Tg mice than that in the non-Tg mice
sensitized with OVA (Fig. 2; p < 0.05).
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A,
CD4+ T cells from OVA-sensitized non-Tg mice
produced IL-4 in response to OVA, whereas the IL-4 production was
significantly reduced in IL-15-Tg mice sensitized with OVA. The IFN-
production in response to OVA was not increased in the
CD4+ T cell population of the sensitized IL-15-Tg
mice. Instead, CD8+ T cells from the
OVA-sensitized IL-15-Tg mice produced an appreciable amount of IFN-
in response to OVA, and such production by CD8+ T
cells was not detected in the OVA-sensitized non-Tg mice (Fig. 3B). IL-4 production in response to OVA was not detected in
the CD8+ T cell population from either
OVA-sensitized non-Tg or IL-15-Tg mice.
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A, CD8+
T cells of IL-15-Tg mice produced a significantly larger amount of
IFN- in response to OVA-DOTAP-treated APC than those of non-Tg mice
did. The production of IFN- by CD8+ T cells
was almost completely inhibited by the addition of anti-MHC class I
mAb to the culture (Fig. 4B). Thus, the increase in IFN-
production in the IL-15-Tg mice is mainly due to the generation of
OVA-specific Tc1 cells after sensitization with OVA.
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Th2 response is inhibited by IFN- produced by Th1 cells,
raising the possibility that CD8+ T cell-mediated
Tc1 responses may be responsible for an impaired allergen inflammation
in the lung following OVA inhalation in IL-15-Tg mice. To test this
hypothesis, CD8+ T cell-depleted mice were
prepared by in vivo administration of anti-CD8 mAb. Both IL-15-Tg
and non-Tg mice were i.p. injected with 400 µg of anti-CD8 mAb or
an isotype control rat IgG 2 days (on day -2) before the first
sensitization with OVA/CFA and 2 days (on day 5) before the second
sensitization with OVA/IFA and then exposed to OVA or PBS every 2 days
from days 14–20 (Fig. 5A). To
confirm whether CD8+ T cells are depleted by this
method, FACS analysis for expression of CD8 in BALF recovered 24 h
after the last inhalation was performed. Consistent with our previous
findings in lymph node of naive IL-15-Tg mice (22), an
increased number of
CD44+CD8+ T cells was
detected in the BALF of the OVA-sensitized IL-15-Tg mice even after PBS
inhalation, and the population was not increased in the IL-15-Tg mice
after OVA inhalation (Fig. 5B). In contrast, the
CD8+ T cells were almost completely depleted in
the BALF of the IL-15-Tg mice exposed to OVA by in vivo administration
of anti-CD8 mAb (Fig. 5B). As shown in Fig. 5C, the number of eosinophils was significantly increased in
the lung of the IL-15-Tg mice treated with anti-CD8 mAb compared
with those treated with control IgG (p <
0.05). The levels of IL-5 and IL-13 in BALF of the IL-15-Tg mice were
also increased due to in vivo depletion of CD8+ T
cells (Fig. 5D). In contrast, the count of eosinophils and
the levels of IL-5 and IL-13 were not changed in the non-Tg mice
treated with anti-CD8 mAb. Thus, in vivo depletion of
CD8+ T cells aggravated the allergic inflammation
in the lung of IL-15-Tg mice following OVA inhalation.
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We next examined the effects of in vivo treatment with
anti-CD8 mAb on the induction of Th2 responses by sensitization
with OVA/CFA and OVA/IFA. We confirmed that CD8+
T cells were almost completely depleted on day 14 in the lymph node and
spleen of non-Tg and IL-15-Tg mice sensitized with OVA/CFA and OVA/IFA
(data not shown). OVA-specific IgE and IgG1 in the sera were
significantly increased in the IL-15-Tg mice following anti-CD8 mAb
administration (Fig. 6A). In
contrast, serum IgG2a level was decreased in IL-15-Tg mice due to
CD8+ T cell depletion. In vivo depletion of
CD8+ T cells did not affect the OVA-specific IgE,
IgG1, or IgG2a level in the serum of non-Tg mice on day 14 after OVA
sensitization.
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B, the
proliferative response to OVA was increased in the IL-15-Tg mice
treated with anti-CD8 mAb. IFN- production was significantly
decreased in OVA-sensitized IL-15-Tg mice after in vivo treatment with
anti-CD8 mAb, whereas IL-4 production was not affected in the
IL-15-Tg mice by in vivo depletion of CD8+ T
cells. These results suggest that CD8+ T
cells are at least partly responsible for impaired IgE production by
OVA sensitization and allergic airway inflammation following OVA
inhalation in IL-15-Tg mice. Effects of adoptive transfer with CD8+ Tc1 cells on allergic inflammation and IgE production
To further determine whether the CD8+ Tc1
cells generated in IL-15-Tg mice act on allergic inflammation at
induction phase or at eliciting phase, we examined the effects of
adoptive transfer with CD8+ T cells derived from
OVA-sensitized IL-15-Tg mice on the allergic inflammation. First,
normal recipient mice were adoptively transferred with
CD8+ T cells from OVA-sensitized IL-15-Tg mice
and then sensitized with OVA/CFA and OVA/IFA at 7-day intervals. Seven
days after the last sensitization, mice were exposed to aerosolized OVA
(Fig. 7A). As shown in Fig. 7, the eosinophila and levels of IL-5 and IL-13 in BALF were significantly
decreased in the recipients, whereas such suppressive effect was not
evident in mice transferred with the CD8+ T cells
from OVA-sensitized non-Tg mice. The suppressive effect on the allergic
inflammation was not detected in mice transferred with
CD8+ T cells from naive IL-15-Tg mice or
casein-sensitized IL-15-Tg mice (data not shown).
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A). IL-4 production by
splenic T cells of the recipients in response to OVA was
significantly decreased in the mice transferred with
CD8+ T cells derived from OVA-sensitized IL-15-Tg
mice, whereas the level of IFN- production was higher in these mice
compared with recipients transferred with CD8+ T
cells from OVA-sensitized non-IL-15-Tg mice.
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IL-15 overexpression did not directly suppress allergic inflammation
Although the impaired airway inflammation in IL-15-Tg mice is
mostly due to insufficient induction of Th2 responses for IgE
production, it is not excluded that the possibility that overexpression
of IL-15 directly suppress pulmonary inflammation in the
lung after OVA inhalation. To test this, we transferred splenic
T cells derived from OVA-sensitized normal mice into IL-15-Tg or non-Tg
mice and then expose these mice to aerosolized OVA. As shown in Fig. 9B, the number of total cells
in the BALF, especially macrophages, was increased in the IL-15-Tg
mice. There was no difference in the number of eosinophils between the
IL-15-Tg mice and non-Tg mice. Surprisingly, the level of IL-5 in the
BALF was rather increased in the IL-15-Tg mice than in non-Tg mice
(Fig. 9C). These results suggest that allergic inflammation
may be exaggerated under the environment of IL-15 overproduction.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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, and generated a significantly lower level of IgE but
a higher level of IgG2a specific for OVA after OVA sensitization.
In vivo depletion of CD8+ T cells by anti-CD8
mAb aggravated the airway inflammation with eosinophilia in the
IL-15-Tg mice. Furthermore, adoptive transfer with
CD8+ Tc1 cells from IL-15-Tg mice suppressed IgE
production with Th2 response against OVA. Overexpression of IL-15 may
shed light on a novel role of CD8+ Tc1 cells in
regulation of allergic diseases such as asthma and provide an insight
into prophylactic and therapeutic approaches for controlling allergic
diseases by IL-15. One of the notable findings in the present study is that OVA-specific CD8+ Tc1 cells are generated in IL-15-Tg mice sensitized with OVA. IL-15 is known to be important for proliferation and maturation of memory-type CD8+ T cells (25, 26, 27, 28). We previously reported that CD8+ T cells expressing memory markers, CD44+, Ly6C+, and CD69- of the phenotype, were increased in naive IL-15-Tg mice (22). Exogenous proteins such as OVA are usually present in association with MHC class II, whereas recent reports have suggested that there is a degree of degeneracy in the processing pathways and that Ags in the extracellular milieu can also be processed and presented in association with MHC class I, which is usually required for activation of CD8+ T cells (29, 30, 31, 32, 33). MacAry et al. (24) reported the existence of OVA-specific, MHC class I-restricted Tc1 cells in the rat i.p. immunized with OVA complexes to the adjuvant aluminum hydroxide. In the present study, we detected significant levels of CD8+ Tc1 responses in both non-Tg and IL-15-Tg mice sensitized with OVA/CFA, when we used OVA-DOTAP couples to load osmotically OVA-peptide on the MHC class I in APC. The CD8+ Tc1 response, which was completely blocked by anti-MHC class I mAb, was significantly higher in the IL-15-Tg mice than in non-Tg mice. It could be speculated that OVA-specific CD4+ and CD8+ T cells may be generated following sensitization with OVA, but the CD8+ Tc1 cells are maintained preferentially in the environment of IL-15 overexpression, resulting in dominant Tc1 responses in IL-15-Tg mice sensitized with OVA.
Our present results with adaptive transfer experiment reveal that
CD8+ Tc1 cells from IL-15-Tg mice significantly
suppressed induction of Th2 response and IgE production. Th1 type
cytokines such as IFN- inhibit Th2 cell proliferation
(34). Thus, production of IFN- by predominant
CD8+ Tc1 response may be responsible for the
impaired Th2 responses in IL-15-Tg mice. In contrast, in vivo treatment
with anti-CD8 mAb did not completely restore Th2 response for IgE
production to OVA sensitization and the allergic inflammation in the
IL-15-Tg mice following OVA inhalation. This may be due to incomplete
depletion of CD8+ T cells by in vivo
administration of anti-CD8 mAb. NK cells (13, 35), NK
T cells (36, 37), and a significant fraction of 
T
cells (26, 27, 38, 39, 40, 41, 42) are also reported to respond to
IL-15. Thus, early production of IFN- by these cells, besides
CD8+ T cells, may be also responsible for the
impaired Th2 responses in IL-15-Tg mice. Zuany-Amorim et al.
(43) recently reported that early production of IL-4 by
T cells is important for IgE response to OVA. It is reported
that T cells express IL-12R1 after stimulation with IL-15 and
produce IFN- in response to IL-12 (40). Therefore, it
is also possible that T cells in IL-15-Tg mice differentiate
into Th1-type cells, not Th2-type cells, resulting in impaired Th2
responses against OVA. This speculation warrants further examination of
the characteristics of the T cells in IL-15-Tg mice.
Although the impaired airway inflammation is mostly due to insufficient
induction of Th2 responses for IgE production in the periphery, the
possibility that overexpression of IL-15 also affects pulmonary
inflammation in the lung in the eliciting phase after OVA inhalation
cannot be excluded. Lack et al. and other investigators
(44, 45, 46, 47, 48) also suggested that nebulized IFN- inhibits
eosinophilic inflammation induced by allergen exposure in
allergen-sensitized mice. In human subjects that underwent an allergen
challenge, relative increases in CD8+ T cells in
BALF have been reported (49). Huang et al.
(50) demonstrated that CD8+ T cells
from normal rats immunized with allergen play a protective role in the
allergen-induced bronchial hyperresponsiveness and eosinophilia through
activation of the Th1 cytokine response. Depletion of
CD8+ T cells with an mAb has been reported to
enhance the airway hyperresponsiveness after OVA challenge in Sprague
Dawley rats, a nonatopic strain that rarely develops airway
hyperresponsiveness. These findings suggest that
CD8+ T cells have a suppressive function in the
airway hyperresponsiveness. The results of the present study showed
increased levels of IL-15 protein and CD44+
CD8+ T cells in BALF of OVA-sensitized IL-15-Tg
mice after OVA inhalation. Therefore, IFN- production by
CD8+ T cells in BALF in response to nebulized OVA
may inhibit IL-5 production and eosinophilia. However,
CD8+ Tc1 cells from IL-15-Tg mice did not inhibit
the allergic inflammation in lung when these T cells were adoptively
transferred at the eliciting phase. Thus, the impaired airway
inflammation in IL-15-Tg mice is mostly due to insufficient induction
of Th2 responses for IgE production.
Mast cells have been shown to respond to IL-15 with a receptor system that does not share elements with IL-2R but uses a 60- to 65-kDa IL-15RX subunit (14). This indicates that IL-15 plays a unique role in the pathological propagation of mast cells that leads to mastcytosis. There are several lines of evidence that IL-15 promotes the effector function of Th2 cells. Mori et al. (17) reported that IL-15 induced IL-5 production of human Th2 clones. IL-15 was stimulated to production of IL-4 by mast cells (51) or CD4+ T cells (52). In addition, IL-15 induces polyclonal Ig production and a proliferation of activated B cells in vitro, corresponds well to the enhancement of IgE and IgG1 (15). In the present study, the allergic airway inflammation was rather exacerbated in IL-15-Tg mice, which developed Th2 response by adoptive transfer with OVA-Th2 cells from normal mice. These results suggest that the overexpression of IL-15 in the lung may aggravate the apparent allergic inflammation well after Th2 response had developed.
Clinical studies have demonstrated that reduced IFN- secretion in
neonates is associated with the subsequent development of atopy
(53, 54, 55). Furthermore, a predisposition toward the
overproduction of Th1 cytokines may protect against atopy, because
patients with multiple sclerosis (56), rheumatoid
arthritis (57), or tuberculosis (58),
conditions associated with increased production of Th1 cytokines, have
a reduced predisposition toward the development of atopy. Thus, the
results of these studies suggest that methods to enhance IFN-
production might be clinically useful in the treatment of allergic
asthma. In the present study, we found that the early production of
IFN- by CD8+ Tc1 cells in IL-15-Tg mice
successfully reversed ongoing Ag-specific Th2-dominated responses
toward Th1-dominated responses. This finding indicates possible
therapeutic effects of IL-15 via up-regulation of Tc1 responses in the
treatment of asthma and allergic diseases. However, because IL-15 is a
pleiotropic cyokine with effects on a number of cell types, it must be
carefully used for patients with apparent allergic inflammation.
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Acknowledgments |
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Footnotes |
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2 Address correspondence and reprint requests to Dr. Yasunobu Yoshikai, Laboratory of Host Defense and Germfree Life, Research Institute for Disease Mechanism and Control, Nagoya University School of Medicine, Nagoya 466-8550, Japan.
3 Abbreviations used in this paper: Tg, transgenic; BALF, bronchoalveolar lavage fluid; OVA-DOTAP, N-[1-(-2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium methyl-sulfate; MMC, mytomycin C.
Received for publication May 31, 2000. Accepted for publication November 14, 2000.
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References |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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in immune regulation. III. Differential selection of TH1 and TH2 murine helper T lymphocyte clones using recombinant IL-2 and recombinant IFN-. J. Immunol. 143:15.[Abstract]
-chain, provisionally designated IL-T, that stimulates T-cell proliferation and the induction of lymphokine-activated killer cells. Proc. Natl. Acad. Sci. USA 91:4940.-chain of the interleukin-2 receptor. Science 264:965. secretion by CD4+ T cells in the absence of TCR ligation. J. Immunol. 161:3408.-positive, Tc1 and Tc0 CD8+ T cell clones mediate the in vivo inhibition of rat IgE. J. Immunol. 160:580. in immune regulation. I. IFN- inhibits the proliferation of Th2 but not Th1 murine helper T lymphocyte clones. J. Immunol. 140:4245.[Abstract]
14 NKT cells by granulocyte/macrophage colony-stimulating factor. Proc. Natl. Acad. Sci. USA 96:7439./+(NK1+ T) cells, natural killer cells, and intestinal intraepithelial T cells. J. Exp. Med. 187:967.- T cells induced by Salmonella infection. J. Immunol. 156:663.[Abstract]
T cell receptor in mice. Eur. J. Immunol. 27:2885.[Medline]
T cells to nonpeptide microbial antigens. J. Immunol. 160:4322.+ intestinal intraepithelial lymphocytes. J. Immunol. 162:1896./IL-7R doubly deficient mice recapitulate the thymic and intraepithelial lymphocyte (IEL) developmental defects of c-/- mice: roles for both IL-2 and IL-15 in CD8 IEL development. J. Immunol. 163:5906. T cells in allergic airway inflammation. Science 280:1265. decreases IgE production and normalizes airways functions in a murine model of allergen sensitization. J. Immunol. 152:2546.[Abstract]
on immunoglobulin E, cellular infiltration, and airway responsiveness in a murine model of allergic asthma. Am. J. Respir. Cell Mol. Biol. 19:826. inhibits the development of secondary allergic responses in mice. J. Immunol. 157:1432.[Abstract]
in asthmatic airways. J. Allergy Clin. Immunol. 95:133.[Medline]
and interleukin-4 in activated human (CD4+) T lymphocytes. Immunology 96:207.[Medline]
and increased production of IL-6 by cord blood mononuclear cells of newborns with a high risk of allergy. Clin. Exp. Allergy. 26:397.[Medline]
in relation to the development of allergic disease during the first 18 months of life. Clin. Exp. Allergy. 25:543.[Medline]
secretion in neonates and subsequent atopy. Lancet 344:983.[Medline]
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) or OVA (
). The production
level of IL-15 protein was expressed as net OD absorbance at 450 nm.
The IL-15 level at the line in the figure was shown as the amount of
the detection limit. Each bar represents data from three independent
experiments using 6- to 8-wk-old mice. *, p <
0.05; **, p < 0.001.
