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*
Division of Oncology, Department of Medicine, and
Division of Immunology and Transplantation Biology, Department of Pediatrics, Stanford University Medical Center, Stanford, CA 94305
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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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2, significantly attenuated the
asthma phenotype in OVA-sensitized and -challenged BALB/c mice
(15, 16). We reasoned that because Th2 cells are necessary
and sufficient for the induction of AHR, factors affecting Th2 immune
responses might influence the development of asthma. One such factor is
the CD81 tetraspanin protein. CD81 (TAPA-1, the target of an anti-proliferative Ab) is a widely expressed cell surface protein involved in a variety of biological responses that has been studied mostly in the context of the immune system (17). On T cells, it associates with CD4 and CD8 and was shown to be involved in T cell differentiation (18, 19, 20). On B cells, it associates in a B cell-specific complex with CD19, CD21, and the IFN-inducible Ag Leu13 (21, 22, 23), with MHC class II molecules (24, 25), with integrins, and with other tetraspanins (26, 27). Functional studies suggest that CD81 is involved in cell motility, adhesion, proliferation, and differentiation (17). CD81-deficient (CD81-/-) mice have an impaired humoral immune responses to protein Ags (28, 29, 30). Chimeric mice, in which only the B cells lacked CD81, were also deficient in Th2 responses as evidenced by their reduced production of Ag-specific IgG1 Ab and IL-4 (31).
The goal of this project was to study the role of CD81 in the context of a physiological Th2-dependent response. For this purpose, we compared the effect of allergen exposure on the development of AHR, airway eosinophil inflammation, and cellular and humoral immune responses in CD81-/- mice and their wild-type littermates. Our results indicate that expression of CD81 is essential for the development of AHR and for local cytokine production although it has no effects on T cell proliferation or on specific IgE response to the allergen.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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CD81-/- mice were generated as described (28) and backcrossed six times to BALB/c mice, obtained from Stanford Medical Center Division of Laboratory Animal Medicine (Stanford, CA). After the fourth backcross, CD81-/- mice could no longer reproduce and had to be maintained as heterozygous animals. Heterozygous mice from the sixth backcrosses were crossed once more to BALB/cByJ mice obtained from The Jackson Laboratory (Bar Harbor, ME). Heterozygous mice from the seventh backcross were bred to produce CD81+/+ and CD81-/- littermates.
Abs and reagents
mAbs were purified from ascites fluid by ammonium sulfate
precipitation and ion-exchange chromatography. We used the following
hybridomas: R4-6A2 (anti-IFN-
), obtained from American Type
Culture Collection (ATCC; Manassas, VA); XMG1.2 (anti-IFN-),
generously provided by T. Mosmann, University of Alberta (Edmonton,
Canada); BVD4-1D11 (anti-IL-4) and BVD6-24G2 (anti-IL-4),
obtained from M. Howard, DNAX Research Institute (Palo Alto, CA);
TRFK-5 and TRKF-4 (anti-IL-5), provided by T. Mosmann; and C17.8
(anti-IL-12), provided by G. Trinchieri, Wistar Institute
(Philadelphia, PA). Mouse anti-OVA IgE mAb was provided by E.
Gelfand, National Jewish Center for Immunology and Respiratory Medicine
(Denver, CO). Recombinant mouse IL-4 was provided by R. Coffman, DNAX
Research Institute. Goat anti-mouse IgG1-peroxidase and goat
anti-mouse IgG2a were purchased from Southern Biotechnology
Associates (Birmingham, AL). R35-72 (anti-mouse IgE), R35-92
(anti-mouse IgE), anti-CD3, anti-CD28, FITC-conjugated
anti-CD3, PE-conjugated anti-CD19, and purified mouse IgE were
all obtained from PharMingen (San Diego, CA). Rat anti-mouse IL-13
mAb, biotin-conjugated goat anti-mouse IL-13, and recombinant mouse
IL-13, IL-2, and IL-12 were obtained from R&D Systems (Minneapolis,
MN). OVA was purchased from Sigma (St. Louis, MO).
Immunization protocols
Mice were immunized i.p. with 100 µg OVA complexed with aluminum potassium sulfate on days 0 and 14 and challenged intranasally with OVA (50 µg in PBS) on days 14, 25, 26, and 27 (OVA/OVA). Control mice received the same initial immunization but were challenged intranasally with PBS (OVA/PBS). AHR to methacholine was measured on day 28. On the next day, blood samples were taken from the tail vein to quantify humoral immune responses. Spleens and peribronchial lymph nodes (LNs) were removed for the analysis of cellular immune responses; BAL fluid and lung samples were taken for evaluation of lung inflammation.
Measurement of airway responsiveness
Airway responsiveness was assessed by methacholine-induced airflow obstruction measured in unrestrained animals using whole body plethysmograph (model PLY 3211; Buxco Electronics, Troy, NY) as described previously (7, 32). Briefly, baseline airway responsiveness was obtained by exposing mice for 2 min to aerosolized 0.9% NaCl (Portable Ultrasonic 5500D; DeVilbiss Health Care, Somerset, PA) and monitoring for the following 5 min. To measure methacholine-induced airflow obstruction, mice were exposed to incremental doses (2.5–20 mg/ml) of methacholine for 2 min each, and airway responsiveness was monitored for 5 min following each dose. The airway reactivity was expressed as enhanced pause (Penh).
Bronchoalveolar lavage
Mice were killed by i.p. injection of a lethal dose of sodium pentobarbital (450 mg/kg). The trachea was cannulated with a 20-gauge i.v. catheter (Johnson & Johnson Medical, Arlington, TX), the lungs were lavaged with 0.8 ml of PBS three times, and cells in the pooled fluid were counted. A portion of BAL cells was put on glass slides and stained with Wright-Giemsa stain (American Master Tech Scientific, Lodi, CA). At least 200 cells were differentiated under light microscopy based on conventional morphological criteria. To obtain the absolute number of each leukocyte subtype in the lavage, the percentages of each cell type were multiplied by the total numbers of cells recovered from the BAL fluid.
Lung histology
Twenty-four hours after AHR measurement, left lungs were removed and fixed in 10% neutral buffered formalin. Paraffin-embedded samples were sectioned and stained with hematoxylin and eosin solution. Sections were also stained with new vital red or periodic acid-Schiff (PAS) to visualize eosinophils and mucous-secreting cells.
Measurement of OVA-specific Igs
Blood was collected from the tail vein in serum separator tubes (Becton Dickinson, San Jose, CA), and serum was obtained by centrifugation at 1500 x g for 5 min. Serum Ab levels were measured by ELISA. OVA-specific IgG1 was determined by coating plates with 5 µg/ml of OVA overnight and blocking 1 h with 5% milk in PBS. Serial dilutions of serum were applied and goat anti-mouse IgG1 peroxidase was used as the detecting Ab. A pool of OVA-sensitized mouse serum was used as standard. The lower detection limit of this assay was 200 ng/ml.
To determine serum OVA-specific IgG2a and IgE levels, plates were coated with goat anti-mouse IgG2a or anti-mouse IgE mAb R35-72 (which does not bind mouse IgG) to capture total IgG2a or IgE in the serum sample. OVA-specific IgG2a or IgE were detected by binding to OVA-biotin. Total IgE was measured by using R35-72 as a capture and R35-92 biotin as a detecting Ab. The standard curves were generated using a 2-fold dilution over 15 wells of purified 200 ng/ml anti-OVA IgG2a, 100 ng/ml anti-OVA IgE, and 500 ng/ml total IgE. The sensitivity of these assays was 6.25 ng/ml for OVA IgG2a and OVA IgE, and 15 ng/ml for total IgE.
Cell culture and cytokine ELISA
Single cell suspension from spleen and peribronchial LNs was
prepared and cultured in RPMI 1640 medium as described
(31). Cells were plated 1.5 x
106 cells/well in 48-well plates and OVA was
added to the wells to a final concentration of 100 µg/ml in a total
volume of 500 µl. After 4 days, the culture supernatant was harvested
and Ag-specific IFN-, IL-4, IL-5, and IL-13 were determined by ELISA
as described (33). The Ab pairs used were as follows,
listed by capture/biotinylated detection: IFN-, R4-6A2/XMG1.2; IL-4,
BVD4-1D11/BVD6-24G2; IL-5, TRFK-5/TRFK-4; and IL-13, rat anti-mouse
IL-13 mAb/goat anti-mouse IL-13 Ab. The detection range was
100–0.195 ng/ml for IFN-, 5000–7.5 pg/ml for IL-4, and 5000–40
pg/ml for IL-5 and IL-13.
Ag-specific proliferation assay
Splenocytes and peribronchial LN lymphocytes were cultured in 96-well plates (2.5 x 105 cells/well) with or without OVA (100 µg/ml) for 4 days. For the last 20 h of culture, cells were pulsed with 1 µCi per well [3H]thymidine (Amersham, Arlington Heights, IL) in 50 µl of medium. The cells were harvested onto filters using a 96-well harvester (Wallac, Turku, Finland) and read on a 96-well format scintillation counter (Wallac).
Flow cytometry
Spleen and peribronchial LNs were harvested and single cell suspensions were prepared as described (31). Cells were then washed with PBS/1% BSA and resuspended at 2 x 107 cells/ml in PBS/1% BSA. Fifty microliters (106 cell) were stained with 1 µg mAb for 30 min on ice, washed two times with PBS/1% BSA, then fixed with 2% paraformaldehyde in PBS for analysis on a FACScan flow cytometer (Becton Dickinson Immunocytometry Systems, San Jose, CA).
T cell purification
Single cell suspension from peripheral LN of naive CD81-/- and CD81+/+ mice was incubated with anti-mouse Thy1.2 Ab-conjugated magnetic beads at 6o-12°C for 15 min. The cells were passed through a MACS-MS+ separation column and bound cells were collected as the T cell fraction. T cell purity, analyzed by FACscan using FITC-conjugated anti-CD3 Ab, was >95%. All Ab-conjugated beads, columns, and magnetic separators were purchased from Miltenyi Biotec (Auburn, CA).
In vitro T cell differentiation assays
Purified T cells (1 x 106) were stimulated on plates coated with anti-CD3 (2 µg/ml) and anti-CD28 (5 µg/ml) in the presence of mouse IL-2 (10 ng/ml). Mouse IL-12 (10 ng/ml) and anti-IL-4 mAb (11B11, 10 µg/ml) were added for Th1 differentiation, and mouse IL-4 (1000 U/ml) and anti IL-12 mAb (C17.8, 10 µg/ml) were added for Th2 differentiation. Cells were stimulated for 7 days, then washed extensively with PBS/2% FBS and restimulated at 106 cells/ml on anti-CD3 and anti-CD28 coated plates in the absence of exogenous cytokine. Supernatants were harvested 24 h later and tested for cytokine levels. For cell proliferation, cells were plated on anti-CD3 and anti-CD28 coated 96-well plates (1 x 105 to 2.5 x 104/well), and [3H]thymidine incorporation during a 24-h restimulation period was determined.
Statistic analysis
The difference of AHR among groups was analyzed with ANOVA using Prism (Intuitive Software for Science, San Diego, CA) and significant ANOVA values between groups were checked by Bonferroni’s multiple comparison tests. Values of p < 0.05 were considered significant.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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To address whether CD81 plays a role in the development of
allergen-induced AHR, mice were immunized i.p. and challenged
intranasally with OVA. In wild-type mice, OVA immunization and
challenges (OVA/OVA) significantly increased AHR. This effect was
dependent upon the intranasal challenge because mice primed with OVA
and challenged with PBS (OVA/PBS) showed very little AHR (Fig. 1
). In marked contrast, OVA-sensitized
and -challenged (OVA/OVA) CD81-/- mice did not
develop a significant increase in AHR and were comparable to their
PBS-challenged controls (OVA/PBS). These results demonstrate that CD81
is important in the development of allergen-induced AHR (Fig. 1).
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Examination of lung tissue of wild-type mice stained with
hematoxylin and eosin revealed widespread patchy inflammatory
infiltrates in the lung after sensitization and intranasal challenge
(OVA/OVA) (Fig. 2A). These
infiltrates were present mainly in the peribronchiolar and perivascular
areas. In contrast, lungs from CD81-/- mice
showed much reduced peribronchiolar and perivascular inflammatory
infiltrates (Fig. 2B). PBS-challenged wild-type and
CD81-deficient mice showed normal lung morphology (Fig. 2, C
and D).
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E). In contrast, there were only very few eosinophils in
lungs of OVA/OVA-treated CD81-/- mice (Fig. 2F). Eosinophils were not present in lungs of PBS-challenged
wild-type or CD81-deficient mice (data not shown). It was also observed
that many airway epithelial cells of OVA/OVA-treated
CD81+/+ mice were enlarged and filled with
homogenous materials, which stained positively for mucin with PAS stain
(Fig. 2G). Airway epithelia from OVA-sensitized and
-challenged CD81-/- mice showed no sign of
hypertrophy and stained negative for mucin (Fig. 2H).
Analysis of BAL fluid of OVA/OVA-treated wild-type mice revealed large
numbers of inflammatory cells, the majority of which were eosinophils
(Fig. 3). In contrast, BAL fluid of
OVA/OVA-treated CD81-/- mice contained fewer
total cells and a trend toward fewer eosinophils, even though their
difference was not statistically significant (Fig. 3).
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Because IgE is thought to be important in the pathogenesis of
allergic responses (34), we measured total and
OVA-specific IgE levels in OVA/OVA-treated wild-type and
CD81-/- mice. In both groups of mice, OVA
sensitization by i.p. immunization was associated with significant
increases in total and OVA-specific serum IgE.
CD81-/- mice produced comparable levels of
total and OVA-specific IgE (Table I).
Unimmunized mice of both groups produced negligible amounts of IgE
(data not shown). These results indicate that the reduction of AHR in
CD81-/- mice is not due to reduced OVA-specific
IgE production.
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augments mouse IgG2a
production and inhibits IgG1 production, whereas the Th2 cytokine IL-4
has the reverse effect (35). Both wild-type and
CD81-/- mice had no detectable level of
OVA-specific IgG1 and IgG2a before immunization. Wild-type mice
responded to OVA immunization and challenge with significant increases
of OVA-specific IgG1 and IgG2a with IgG1 being predominant. Although
CD81-/- mice responded in a similar manner,
their specific IgG1 response was generally decreased (Table I).
However, because of large variations in OVA-specific Ab levels within
the same group of mice, the difference in OVA-specific Ig levels
between OVA/OVA-treated CD81-/- and
CD81+/+ mice was not significant. The total IgG
levels between the two strains were not significantly different before
and post OVA immunization (prior: CD81-/-
2367 ± 619 µg/ml; CD81+/+ 1655 ±
392 µg/ml; post: CD81-/- 5841 ± 2363
µg/ml; CD81+/+ 4503 ± 1688 µg/ml).
These results suggest that the reduced AHR and lung inflammation in
CD81-deficient mice are not associated with reduced OVA-specific
humoral immune responses. Comparable Ag-specific lymphocyte proliferation in CD81-/- and CD81+/+ mice
To determine whether the difference in AHR was associated with a
difference in cellular immune responses, peribronchial LN lymphocytes
and splenocytes from OVA-sensitized and -challenged (OVA/OVA)
CD81-/- and CD81+/+ mice
were cultured in the presence or absence of 100 µg/ml of OVA for 4
days. During the last 20 h of culture, cells were pulsed with
[3H]thymidine and cell proliferation was
measured. Both CD81+/+ and
CD81-/- lymphocytes responded to OVA with a
similar rate of cell proliferation (Fig. 4), indicating that both the draining LNs
and the spleens of CD81-/- mice contained
OVA-specific T cells, which were capable of responding to the Ag in
vitro.
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Given the correlation between allergic airway disease and
increased expression of Th2 cytokines by lung T cells, it was of
interest to determine whether the reduced AHR and lung inflammation in
CD81-/- mice reflected a change in their
OVA-specific cytokine responses. As expected, splenocytes and
peribronchial LN lymphocytes of wild-type mice produced considerable
amounts of IL-4, IL-5, and IL-13 in response to OVA (Fig. 5, A–C, respectively). In
contrast, the production of Th2 cytokine by
CD81-/- peribronchial LN cells was reduced
15-fold (IL-4), 2-fold (IL-5), or was undetectable (IL-13) (Fig. 5, A–C, respectively). The effect on local cytokine production
was less pronounced systemically as CD81-/-
splenocytes produced about half the amounts of IL-4 and IL-13 as
compared with CD81+/+ splenocytes (Fig. 5, A and C) and comparable low levels of IL-5 (Fig. 5B).
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, peribronchial LN
cells secreted negligible levels of this cytokine. However, IFN-
levels were reduced in both splenocytes and peribronchial LNs derived
from CD81-/- mice (Fig. 5D). Reduced numbers of B cells in peribronchial LN and spleen of immunized CD81-/- mice
The reduced cytokine profiles secreted in vitro by OVA-stimulated
CD81-/- T cells could be due to an imbalance of
lymphoid subsets in these organs. To test this notion, the composition
of lymphoid cells in spleen and peribronchial LNs was analyzed using T
(FITC-conjugated anti-CD3 mAb) and B (PE-conjugated anti-CD19
mAb) cell markers after immunization and challenge with OVA. The
proportion of B and T cells were identical in unimmunized
CD81-/- and CD81+/+ mice
(Refs. 28, 29, 30 and data not shown). However, in response to
immunization the percentage of B cells was reduced considerably in
peribronchial LN and to a lesser degree in spleens of
CD81-/- mice in comparison with
CD81+/+ mice (Table II). Conversely, the T cell percentage of
CD81-/- mice was slightly but consistently
higher than that seen in CD81+/+ mice (Table II).
Because Ag-specific B cells function as potent APC in secondary immune
responses (36), the reduction of B cells in
CD81-/- mice might have contributed to reduced
cytokine production.
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Having shown that the reduced cytokine production in
CD81-/- mice was not due to a reduction in T
cell numbers, it was important to determine whether
CD81-/- T cells were intrinsically deficient in
cytokine production. Therefore, we tested whether cytokine responses of
T cells from naive CD81-/- differed from those
of CD81+/+ mice when induced to secrete Th1 and
Th2 cytokines under polarizing stimulation conditions. T cells from all
experimental conditions showed identical high levels of proliferation
(Fig. 6A). IL-12 induced the
polarization of CD81+/+ and
CD81-/- T cells to the Th1 phenotype,
characterized by high level of IFN- and very little IL-4 production.
Conversely, IL-4 induced the Th2 phenotype characterized by a high
level of IL-4 and a very low level of IFN- production.
CD81-/- and CD81+/+ T
cells produced comparable levels of IFN- and IL-4 in response to Th1
or Th2 stimuli, respectively (Fig. 6B). These results
suggest that the reduced cytokine production in immunized
CD81-/- mice was not due to an intrinsic defect
in their T cells.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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). In addition,
allergen-induced lung inflammation, eosinophilia, and mucous cell
hyperplasia are also reduced in CD81-/- mice
(Figs. 2 and 3). These reduced responses are associated with a marked
decrease in cytokine production by peribronchial LN cells (Fig. 5).
Interestingly, reduced AHR in CD81-/- mice is
not due to deficient production of Ag-specific IgE because levels of
anti-OVA IgE in these mice are comparable to those of wild-type
mice (Table I). These results provide the first evidence that CD81 is
necessary for the development of allergen-induced AHR. Previous studies of unimmunized CD81-/- mice have demonstrated that T and B cell numbers in various lymphatic compartments were similar to those seen in normal mice (28, 29, 30). However, T cells from CD81-/- mice show enhanced proliferative responses to polyclonal and allogenic stimuli (29), while B cells of CD81-/- mice express low levels of CD19 and respond poorly to stimulation with anti-IgM Abs (Ref. 29 ; our unpublished results). Nevertheless, B cells from CD81-/- mice are capable of normal Ig production, as seen by their response to T-independent Ags (28, 30).
In contrast, the response of CD81-/- mice to T-dependent Ags is impaired and was most evident under conditions that elicit Th2-type responses (28). This impairment was further analyzed in B cell-deficient chimeric mice, reconstituted with CD81-/- B cells. Again, these mice exhibited an impaired Th2 response implicating a deficiency in the CD81-/- B cell compartment (31).
Because CD4+ Th2 cells play a crucial role in
initiating and sustaining allergen-induced airway responses (2, 3, 8) and because CD81 is necessary for proper Th2 responses, we
examined the role of CD81 in local and systemic cytokine production in
an allergen-induced AHR model. Our results demonstrate that CD81 is
important for allergen-induced cytokine production, especially for
local Th2 cytokine production by peribronchial LN (Fig. 5). Production
of IFN-, the Th1 cytokine, although low to begin with, was reduced
in the CD81-/- mice compared with their
wild-type littermates. The impairment in cytokine secretion was not due
to reduced OVA-specific T cell response because a similar proliferative
response was seen in CD81-/- and wild-type mice
(Fig. 4). Nor was it due to decreased T cell numbers (Table II) or to
an innate ability of CD81-/- T cells to produce
cytokines. This was supported by evidence that when naive
CD81-/- T cells were stimulated in vitro with
anti-CD3 and anti-CD28 in the presence of either IL-12 or IL-4,
they could polarize into Th1 and Th2 phenotypes, respectively, and were
able to produce normal levels of IFN and IL-4 (Fig. 6).
It is likely that the reduced B cell number in OVA-immunized and
-challenged CD81-/- mice (Table II) contributes
to reduced cytokine production because Ag-specific B cells function as
potent APCs in response to cognate Ag (36). In contrast,
we have demonstrated that T cells of CD81-/-
mice have the ability to respond to the Ag and the innate ability to
produce cytokines. Thus it is possible that the deficiency in their
interactions with B cells and other APCs is the cause for the impaired
Th2 immune response in vivo.
Reduced local Th2 cytokine production in OVA/OVA-treated mice is most
likely the cause of reduced lung eosinophil infiltration (Figs. 2 and 3). IL-4, IL-5, and IL-13 are all involved directly or indirectly in
the development of eosinophilic lung inflammation in murine asthma
models. IL-5 has been considered a major player in promoting the
activation and maintenance of eosinophils in tissues (37, 38). IL-4 may contribute to pulmonary eosinophilia directly by
inducing endothelial VCAM-1 expression, which together with integrin
4ß1 expression on eosinophils increases
eosinophil adherence to the vessels (39, 40). IL-4 may
also contribute to pulmonary eosinophilia indirectly via its effect on
Th2 response and IL-5 synthesis. IL-13 not only activates eosinophils
and promotes their differentiation (41, 42), it also
enhances eotaxin expression by airway epithelial cells
(43). Because these Th2 cytokines were reduced in
CD81-/- mice, it is possible that CD81 may
affect allergen-induced pulmonary eosinophilia through regulation of
local Th2 cytokine production. However, CD81 may also directly
influence eosinophil maturation and function because CD81 expression is
increased when human eosinophils are induced to mature by helminth or
by exposure to cytokines (IL-13 and GM-CSF) (44). In
addition, stimulation of human eosinophils with anti-CD81 mAb
causes down-regulation of L-selectin, a sign of eosinophil activation
(45).
Lack of CD81 was also associated with reduced mucous cell hyperplasia
and mucous secretion (Fig. 2), which may also be due to reduced Th2
cytokine production. Several recent studies have demonstrated that IL-4
plays an important role in airway goblet cell differentiation and
mucous secretion. For example, blockage of IL-4 receptor prevented
Ag-induced mucous-containing cells (46), and addition of
IL-4 to the culture medium induces MUC2 gene expression and
mucous glycoconjugate production in a cultured epithelial cell line
(47). In addition, neutralization of IL-13 prevents
allergen-induced increase in mucous-containing cells in the airway
(16). Thus, the reduced mucous secretion in
CD81-/- mice was most likely a secondary event
following reduced IL-4 and IL-13 production.
Epidemiological data have demonstrated an association between elevated
IgE levels and bronchial asthma (48). It is believed that
increased IgE levels contribute to AHR by binding the IgE-Fc receptor,
thereby inducing mast cell degranulation. Upon degranulation, mast
cells release a variety of mediators such as bronchoconstrictors, which
may contribute to the development of AHR (49, 50). Here we
show that CD81-/- mice display no AHR after OVA
sensitization and challenge even though they have normal levels of
total and allergen-specific IgE (Table I). It should be noted that CD81
has been previously implicated in mast cell degranulation. Fleming et
al. have used an assay aimed at identifying molecules that will inhibit
IgE-induced mast cell degranulation and have identified an
anti-CD81 mAb as such an inhibitor (51). Thus,
it is possible that the reduced AHR in the presence of comparable IgE
levels, as seen in CD81-/- mice, could be due
to a failure of mast cells to degranulate in response to
IgE-cross-linking.
In summary, our results demonstrate that CD81 is essential for the development of allergen-induced AHR. It is likely that disruption of CD81 negatively affects AHR mainly by reducing local Th2 cytokine response, which, in turn, regulates lung inflammation and mucous production in the airway. In addition, CD81 may affect mast cell degranulation and eosinophil functions. Further dissection of the immunological and physiological defect of these mice may provide targets for the development of new antiasthma therapies.
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Acknowledgments |
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Footnotes |
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2 Address correspondence and reprint requests to Dr. Shoshana Levy, Department of Medicine/Oncology, Room 1105a CCSR, Stanford University Medical Center, Stanford, CA 94305.
3 Abbreviations used in this paper: AHR, airway hyperreactivity; BAL, bronchoalveolar lavage; LN, lymph node; PAS, periodic acid-Schiff.
Received for publication May 23, 2000. Accepted for publication July 31, 2000.
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 A. Cherukuri, T. Shoham, H. W. Sohn, S. Levy, S. Brooks, R. Carter, and S. K. Pierce The Tetraspanin CD81 Is Necessary for Partitioning of Coligated CD19/CD21-B Cell Antigen Receptor Complexes into Signaling-Active Lipid Rafts J. Immunol., January 1, 2004; 172(1): 370 - 380. [Abstract] [Full Text] [PDF]
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 J. Deng, R. H. Dekruyff, G. J. Freeman, D. T. Umetsu, and S. Levy Critical role of CD81 in cognate T-B cell interactions leading to Th2 responses Int. Immunol., May 1, 2002; 14(5): 513 - 523. [Abstract] [Full Text] [PDF]
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K. L. Clark, Z. Zeng, A. L. Langford, S. M. Bowen, and S. C. Todd PGRL Is a Major CD81-Associated Protein on Lymphocytes and Distinguishes a New Family of Cell Surface Proteins J. Immunol., November 1, 2001; 167(9): 5115 - 5121. [Abstract] [Full Text] [PDF]
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 Y. Takahashi, D. Bigler, Y. Ito, and J. M. White Sequence-Specific Interaction between the Disintegrin Domain of Mouse ADAM 3 and Murine Eggs: Role of {beta}1 Integrin-associated Proteins CD9, CD81, and CD98 Mol. Biol. Cell, April 1, 2001; 12(4): 809 - 820. [Abstract] [Full Text]
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M. E. Hemler Specific tetraspanin functions J. Cell Biol., December 24, 2001; 155(7): 1103 - 1108. [Abstract] [Full Text] [PDF]
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