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Keywords:

  • asthma;
  • occupational diseases;
  • rhinitis;
  • sputum;
  • T cells

Abstract

  1. Top of page
  2. Abstract
  3. Materials and methods
  4. Results
  5. Discussion
  6. Acknowledgment
  7. References

Background:  Allergic asthma and rhinitis are described as associated with a Th2 activation. However, recent works indicate that a Th1 activation can also be associated with these diseases, concomitantly to a defect in regulatory T (Treg) cell activation. Occupational asthma (OA) and occupational rhinitis (OR) are peculiar cases of these diseases in which the T-cell activation profile is largely unknown.

Objective:  To characterize T-cell activation induced after a specific inhalation test (SIT) in OA and OR.

Material and methods:  A total of 21 subjects with OA, 10 subjects with OR, 10 exposed nonallergic (ENA) subjects, and 14 healthy volunteers were included. The SIT with the incriminated substance was performed in patients and ENA subjects. Blood and induced sputum were obtained before and after SIT. T cells were analysed for CD69, CD25, IL-13, and IFN-γ expression by flow cytometry. IL-4 and IFN-γ were assayed by enzyme-linked immunosorbent assay (ELISA) in cell culture supernatants. Treg cells were identified as CD4+CD25+highCD45RO+CD69 T cells in peripheral blood.

Results:  Baseline IFN-γ production was decreased in OA and OR compared with controls. The SIT induced an increase in both Th1 and Th2 cells in blood and sputum from OA. In this group, the proportion of peripheral Treg cells decreased after SIT. Similar results were found in the CD8+ population. ELISA assays were concordant with flow cytometry. In OR, an attenuated activation profile was found, with an increase in the proportion of IL-13-producing T cells after SIT. By contrast, in ENA subjects, SIT induced Th2 activation, with an increase in Treg cells and a decrease in Th1 cells.

Conclusions:  Our results demonstrate a gradient of T-cell activation from a tolerating profile in ENA subjects to an inflammatory profile in OA, with an intermediate stage in OR.

Occupational factors have been implicated in 9–15% of adult asthma (1), making occupational asthma (OA) the main cause of occupational respiratory diseases. As a result of the large diversity of causative agents, the pathophysiology of OA is still controversial. It is admitted that immunological and nonimmunological reactions can be involved, and among the former, IgE-dependent and IgE-independent immune responses. IgE-dependent OA is mainly because of high molecular weight (>5000 day) molecules, such as vegetable proteins, and thought to be closely related to asthma unrelated to work. Low molecular weight agents such as isocyanates, aldehydes and other chemicals induce a form of asthma in which the implication of IgE is doubtable (2). However, in both cases of immunological OA, the airway inflammation is similar, with the presence of eosinophils, lymphocytes and mast cells (1). Previous studies in mice have demonstrated a Th2 cell activation, with an increase in IL-5 and IL-4 production in experimental OA (3, 4). Other mice studies have found a Th1 activation associated with the Th2 activation previously described, especially in the case of low molecular weight allergen exposure, with IFN-γ production (5, 6), notably by the CD8+γδ T cells (7). This view is reminiscent of what is currently known in non-occupational asthma, in which a Th2 activation predominates, accompanied by a Th1 activation (8). In addition, in non-occupational asthma, some evidences recently indicated that Th2 and Th1 cell activation could be concomitantly associated with a decrease in the regulatory T (Treg) cell frequency and activation (9). However, to date, no data about Treg cells in OA, in response to a specific inhalation test (SIT), have been published.

Occupational asthma is frequently preceded by occupational rhinitis (OR), notably in cases related to high molecular weight agents (1). Many studies clearly established that allergic rhinitis is Th2-mediated (10). In addition, a Th1 activation was also observed in allergic rhinitis during natural allergen exposure (11), and a deficiency in the Treg cell activation was clearly demonstrated in this disease (12). However, no report concerns specifically the immunopathology of OR.

The aim of this study was thus to characterize the human T-cell activation induced by occupational allergens, in OA and OR subjects. We took advantage, for this purpose, of SIT performed to diagnose an OA or rhinitis.

Materials and methods

  1. Top of page
  2. Abstract
  3. Materials and methods
  4. Results
  5. Discussion
  6. Acknowledgment
  7. References

Study population

Patients referred to our institution for clinical suspicion of OA and/or rhinitis were consecutively included from January 2003 to July 2005. Occupational asthma was diagnosed on a history of chronic cough and wheezing dyspnea exacerbated at work and improved during out-of-work periods, in patients with a positive methacholine test at least after SIT, and a positive SIT. Occupational rhinitis was diagnosed on chronic rhinorrhea and/or nasal obstruction, with sneezing and nasal itching, increased at work and improved out of work, with triggering of nasal symptoms during SIT. In addition, these patients had to display a negative SIT on lung function and a negative methacholine test. For high molecular weight allergens, skin prick tests were performed with commercial extracts (Stallergenes, Antony, France) (cereal flours and latex), or the native vegetable (cauliflower). For low molecular weight substances, SIT was the only diagnosis method used.

A total of 14 healthy volunteers and 10 exposed nonallergic (ENA) workers to OA-inducing substances were included as controls. Healthy volunteers and ENA subjects were nonsmokers, and displayed normal pulmonary function with negative methacholine test.

All subjects gave a written informed consent, and the protocol was approved by the ethical committee Comité de Protection des Personnes Marseille 2.

Methacholine test

After baseline spirometry and plethysmography with measurement of airway resistance (Raw) and functional residual capacity according to the method of Dubois et al. (13), patients inhaled successive doses of methacholine (40, 60 μg, and 4 times 100 μg), using an automatic dosimeter (ME-FAR; Electromedicali, Breschia, Italy). The Raw and forced expiratory volume in 1 s (FEV1) were measured after each inhalation. The test was stopped when Raw increased by three times or when FEV1 fell by 20%. Two puffs of albuterol (100 μg) were given thereafter to reverse the bronchial obstruction. The test was considered positive if Raw doubled and FEV1 dropped by more than 20% for a dose below 200 μg of methacholine (14).

Specific inhalation tests

Anti-asthmatic medications were withheld according to their duration of action. The SITs were carried out in 5 m3 room equipped with an exhaust ventilation system and a small electric fan to ensure air mixing (15). The SIT was performed only in subjects with baseline FEV1 > 70% of predicted value.

Patients were progressively exposed to the respective suspected occupational agent in a dose as close as possible as the occupational usage, for a total duration of 60 min. Maximal expiratory volumes were measured before, every 5 min of exposure for the first 15 min of the procedure, and every 10 min till the end of the challenge. Patients were then kept in hospital and FEV1 was measured each hour till 6 h after the challenge to monitor any late-phase reaction. The test was considered as positive if FEV1 dropped below 80% of the baseline value. In case of asthmatic reaction during SIT, the procedure was stopped. In case of a decrease of the FEV1 below 80% of baseline value, the patient was given 200–1000 μg of albuterol to reverse the bronchial obstruction.

Nasal symptoms were monitored throughout the procedure and the presence of sneezing, rhinorrhea, nasal obstruction and pruritus were checked before each spirometry. Specific inhalation test was considered as positive for OR if significant nasal symptoms were triggered.

Induced sputum

Sputum was induced with hypertonic saline (4.5%) aerosol. Immediately, cellular plugs were separated from saliva and incubated with 0.1% dithiothreitol. Cells were filtered through 40-μm cell strainer, washed, and resuspended in RPMI® (Gibco, Cergy-Pontoise, France) at a concentration of 106 cells/ml. Total nucleated cell counts and viability were assessed after trypan blue exclusion. Samples were validated by a viability >50% and a salivary cell contamination <20%, according to ERS guidelines (15). Cells were then cytospined on silane-coated slides (Sigma-Aldrich, Lyon, France) and stained with May-Grunwald-Giemsa coloration (Sigma-Aldrich). Results were expressed as percentages of leucocytes.

Assessment of T-cell activation

Whole blood cells were cultured at 37°C, 5% CO2 in complete medium [RPMI 1640 10% heat-inactivated fetal calf serum, 100 U/ml penicillin G, 100 μg/ml streptomycin, 2 mM/glutamine, pyruvate and 2-mercaptoethanol (Gibco)]. IFN-γ and IL-13 were assessed by flow cytometry after 6 h of stimulation by PMA (50 ng/ml; Sigma-Aldrich) and ionomycin (2 μg/ml, Sigma-Aldrich) plus monensin (2 μM) (Sigma-Aldrich).

Surface antibodies coupled to fluorochromes [anti-CD3-Cy5PE, anti-CD8-Cy5PE, anti-CD8-PE, anti-CD25-PE, anti-CD45RO-FITC, anti-CD69-APC (Immunotech, Marseilles, France), anti-CD3-FITC, anti-CD4-Cy5PE, anti-CD4-APC (Dako, Trappes, France)] were added at the recommended concentration in 50 μl of whole blood. Cells were fixed in formaldehyde 4% for 10 min, and permeabilized with saponine 0.1%. Intracellular antibodies [anti-IFNγ-FITC (Pharmingen, Le pont de Claix, France) and anti-IL13-PE (R&D system, Lille, France)] were added at the recommended concentrations for 30 min, cells were suspended in formol 0.1% before flow cytometric analysis. For each surface or intracellular staining, positive cells were identified by comparison to the fluorescence of cells stained with control IgG isotypes (Immunotech).

Fluorescence was detected with a 15 mW argon ion laser on a three-color FACScalibur® flow cytometer (Becton Dickinson, Franklin Lakes, NJ, USA). Standard acquisition and analysis were obtained through Cellquest Software (Becton Dickinson).

CD4+CD25+high T cells were considered as Treg cells based on the CD4+CD25+highCD45RO+C69 phenotype. This subset was only studied in the peripheral blood samples because of too few cells recovered with induced sputum.

Enzyme-linked immunosorbent assay

IFN-γ and IL-4 were assessed by enzyme-linked immunosorbent assay (ELISA) in cell culture supernatants in wells cultured without monensin. Enzyme-linked immunosorbent assay was carried out according to manufacturer instructions. IFN-γ and IL-4 Duoset® were obtained from R&D Systems. IFN-γ and IL-4 assay sensitivity was of 15 pg/ml.

Statistical analysis

Results were expressed as mean ± standard error. Data were normally distributed as indicated by graphic representation of the data and negative Kolmogorov-Smirnof test. Variations among controls, ENA subjects, OR, and OA patients were performed using anova. If the anova indicated significant variation of the mean, comparisons were carried out using parametric unpaired t-test between controls and the three other groups. Results obtained after specific challenge were compared with baseline by paired t-tests. A P-value below 0.05 was considered as statistically significant. Analyses were carried out using the Statview® software (SAS, Cary, NC, USA).

Results

  1. Top of page
  2. Abstract
  3. Materials and methods
  4. Results
  5. Discussion
  6. Acknowledgment
  7. References

Subjects

A total of 44 subjects (mean age 43 ± 6 years) were investigated for suspected OA or OR. After SIT, 21 were considered as OA, 10 as OR and 13, in whom SIT was negative, were excluded (Table 1). A total of 14 OA were exposed to low molecular weight allergens: 3 painters (isocyanates), 3 hospital workers (formaldehydes), 4 hairdressers (persulfates), 1 dental prosthesis manufacturer (diacrylate), 1 photographer (diacrylate), 1 ink industry worker (diacrylate), and 1 chemical industry worker (epoxy resin). Among the seven workers exposed to high molecular weight agents, three hospital workers were allergic to latex, two bakers were allergic to cereal flours, one vegetable merchant was allergic to cauliflower and a joiner was considered as allergic to wood dusts. Among OR, six patients were exposed to low molecular weight agents: formaldehydes in a hospital worker, persulfates in three hairdressers, aliphatic amines in a chemistry industry worker and diacrylates in a photographic processing worker. High molecular weight agents were incriminated in four patients: Cereal flour in two bakers, wood dust in a joiner and latex in a health care worker. Allergy to high molecular weight allergens was documented by positive skin prick tests at the exception of wood dust allergy. Ten ENA patients (mean age 32 ± 3 years) were included, among which two nurses were exposed to latex, a laboratory technician, a cleaner, a hospital worker, and a building worker were exposed to formaldehydes, a painter and a coachbuilder were exposed to isocyanates, and a chemical industry worker was exposed to epoxy (Table 1). All ENA subjects displayed negative methacholine test and SIT. Fourteen healthy subjects (mean age 31 ± 5 years) with negative methacholine test were included as controls. Specific inhalation test was performed in patients and ENA subjects only.

Table 1.   Patient characteristics
GenderSuspected allergenFEV1
  1. F, female; M, male; FEV1 given in percentage of predicted value.

Asthma
 FIsocyanate88
 FLatex91
 MWood82
 MIsocyanate118
 FIsocyanate85
 FPersulfates104
 MFlour110
 MDiacrylates120
 MDiacrylates78
 FFormaldehydes83
 MDiacrylates76
 FLatex69
 FLatex71
 FFormaldehydes101
 MEpoxy92
 FFlour97
 FFormaldehydes89
 MPersulfates76
 MCabbage88
 MPersulfates79
 FPersulfates101
Rhinitis
 FFormaldehydes101
 MFlour125
 FLatex105
 FPersulfates95
 MWood96
 FAmine90
 FPersulfates100
 MDiacrylates121
 MFlour103
 MPersulfates103
Exposed nonallergic subjects
 MLatex98
 MFormaldehydes110
 MFormaldehydes92
 FAmine88
 FFormaldehydes79
 FLatex120
 MIsocyanate105
 MFormaldéhydes76
 MIsocyanates88
 FEpoxy119

Induced sputum cell counts

Valid induced sputum was obtained in 18 OA, 4 OR, and 7 ENA subjects. As the number of valid samples from OR was less than five, results were not analysed in this group. Eosinophils were increased in OA compared with controls at baseline, and significantly increased further after SIT (P < 0.05) (Fig. 1). In ENA subjects, sputum cell counts did not differ from controls and did not vary after SIT.

image

Figure 1.  Induced sputum differential cells counts. Induced sputum cells were recovered in occupational asthma and exposed nonallergic individuals, before specific inhalation test (SIT) data are compared to control data by an unpaired t-test (p values indicated in the ‘before SIT’ columns); after SIT data are compared to before challenge data by a paired t-test (p values indicated in the ‘after SIT’ columns). Differential cell counts were obtained after cytospin and May-Grunwald-Giemsa staining. *P < 0.05, **P < 0.005 ***P < 0.0005. SIT, specific inhalation test. Results expressed as mean ± standard error.

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T-cell activation

The CD69 expression was not different in blood T cells in patients compared with controls and did not vary upon SIT (Table 2).

Table 2.   Blood T-cell phenotype and cytokine production
 Controls (n = 15)Exposed nonallergic subjects (n = 10) Rhinitis (n = 10) Asthmatics (n = 21)
Before SITAfter SITBefore SITAfter SITBefore SITAfter SIT
  1. Results are expressed as mean ± standard error.

  2. *P < 0.05.

  3. **P < 0.0005. Before specific inhalation test (SIT), data are compared with control data by an unpaired t-test (P-values indicated in the ‘before SIT’ columns); After SIT data are compared with before challenge data by a paired t-test (P-values indicated in the ‘after SIT’ columns).

  4. ***P < 0.005.

Flow cytometry (% of positive cells)
 CD3+CD69+9.86 (±2.6)11.63 (±1.09)11.80 (±2.1)10.17 (±1.5)11 (±2.68)9.24 (±3.9)10.5 (±3.12)
 CD3+IL13+1.01 (±0.2)0.63 (±0.05)1.98 (±0.91)*0.87 (±0.15)1.52 (±0.36)*1.05 (±0.18)2.34 (±0.5)**
 CD8+IL13+0.6 (±0.11)0.85 (±0.37)0.48 (±0.12)0.8 (±0.11)1.08 (±0.22)*1.6 (±0.45)2.79 (±0.77)***
 CD3+IFN-γ+18.32 (±2.23)19.25 (±3.61)13.79 (±2.68)*9.89 (±1.2)***11.46 (±1.4)12.77 (±1.45)*15.78 (±1.55)*
 CD8+IFN-γ+27.1 (±2.86)26.00 (±5.96)19.96 (±2.71)13.9 (±1.14)***13.5 (±2.2)19.9(±1.98)*24.06 (±2.6)*
 CD4+CD25+7.87 (±1)8.71 (±0.95)11.72 (±1.58)*7.5 (±1)6.32 (±0.5)7.24 (±1)5.4 (±0.7)*
ELISA (pg/ml)
 IFN-γ39366 (±5194)30290 (±6856)14977 (±1996)*24198 (±7813)22866 (±6972)40164 (±4572)47129 (±5953)***
 IL-479 (±8.5)108 (±27.44)138 (±22.5)86 (±19)142 (±24)*110 (±22.4)130 (±24.3)*

The baseline proportions of IL-13-producing T cells were similar between groups. After SIT, the proportions of CD3+ and CD8+ IL-13+ cells increased in both OA and OR (Fig. 2A). Concordant results were found by ELISA with regard to IL-4, which significantly increased after SIT in both groups (P < 0.05) (Table 2). In OA, SIT induced an increase in CD3+ but not in CD8+IL13+ cells, and a nonsignificant IL-4 increase.

image

Figure 2.  Blood T-cell activation in occupational asthma (OA) and rhinitis, and in exposed nonallergics (ENA). (A) Percentages of blood IL-13-producing T cells before and after specific inhalation test (SIT) in OA and rhinitis, in ENA subjects and in controls. (B) Percentages of blood IFN-γ-producing T cells before and after SIT in OA and rhinitis, in ENA subjects and in controls. (C) Percentages of blood CD4+CD25+highCD45RO+CD69 T cells before and after SIT in OA and rhinitis, in ENA subjects and in controls. *P < 0.05, **P < 0.005, ***P < 0.0005. Results expressed as % ± SEM.

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At baseline, IFN-γ+ cells were decreased in both groups of patients compared with controls, both in the whole T-cell population and in the CD8+ subset (Fig. 2B). Specific inhalation test increased the percentage of IFN-γ-producing T cells in OA but not in OR. Again this result was found at the CD3+ and the CD8+ level (Table 2). This result was confirmed by ELISA in culture supernatants, with an increase in IFN-γ levels after SIT compared with baseline in OA (P < 0.005) (Table 2). By contrast, in ENA subjects, SIT decreased the percentage of CD3+IFN-γ+ cells (Fig. 2B). This decrease was significant at the level of the whole T-cell population (CD3+) only. In cell culture supernatants, results were concordant with a decrease by 50% of IFN-γ levels (Table 2).

No difference was found among groups before challenge, regarding the proportion of the CD4+CD25+highCD45RO+CD69 Treg cell population. After SIT, OA patients displayed a significant decrease in the regulatory T-cells population (P < 0.05) (Fig. 2C). By contrast, in ENA subjects, a significant increase in Treg cell percentages occurred after SIT.

Specific inhalation test increased induced sputum CD69+ (P < 0.005), IFN-γ+ (P < 0.05) and IL-13+ (P < 0.05) T-cell proportions in OA patients (Fig. 3).

image

Figure 3.  Induced sputum T-cell activation in occupational asthma (OA). (A) Percentages of induced sputum IFN-γ-producing T cells before and after SIT in OA. (B) Percentages of induced sputum IL-13-producing T cells before and after specific inhalation test (SIT) in OA. (C) Percentages of induced sputum CD3+CD69+ T cells before and after SIT in OA. *P < 0.05, **P < 0.005. Results expressed as % ± SEM.

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Comparisons according to exposure to low or high molecular weight agents

Results obtained in OA and OR were then analysed according to the type of putative causal agent. In all cases, results were concordant in both groups, although not necessarily significant, because of small effectives. Results are showed for CD3+IL13+, CD3+IFN-γ+, and Treg cells in Fig. 4.

image

Figure 4.  T-cell activation according to type of exposure. (A) Percentages of blood IFN-γ-producing T cells before and after SIT in OA or rhinitis. (B) Percentages of blood IL13-producing T cells before and after specific inhalation test (SIT) in occupational asthma (OA) or rhinitis. (C) Percentages of blood Treg cells before and after SIT in OA or rhinitis. *P < 0.05, **P < 0.005, ***P < 0.0005. Results expressed as % ± SEM.

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Discussion

  1. Top of page
  2. Abstract
  3. Materials and methods
  4. Results
  5. Discussion
  6. Acknowledgment
  7. References

Allergic asthma is characterized by Th2 activation, mainly attributed to CD4+ T cells, which, by producing IL-4 and IL-5, respectively, induce IgE production and bronchial eosinophilia, two main features of asthma. This concept, named the Th2 paradigm in allergy, is to date considered as a dogma in asthma pathophysiology (16).

Despite an intrinsic defect in Th1 cells concordant with this Th2 paradigm, we found that in OA patients, SIT induced a mixed Th2/Th1 response. In addition, CD8+ cells were the main producers of IFN-γ.

In OA, the T-cell activation was previously studied in a murine model of isocyanate-induced asthma, a major form of OA because of a low molecular weight allergen. In this model, the implication of T cells was clearly demonstrated. Indeed, T cells from sensitized animals were sufficient to transfer the disease to naïve mice (17). Conversely in CD4- but also in CD8-deficient mice, isocyanate-induced airways hyper-responsiveness was impaired, together with airways eosinophilia and specific IgE production. A Th2 activation was demonstrated, with an increase in IL-4 and IL-5 production, but also a Th1 activation mainly characterized by IFN-γ increase (6). In humans, hyper-responsive to isocyanates, bronchial biopsy studies have long been established an in situ activation of eosinophils, CD4+ and CD8+ T lymphocytes (18). Therefore, animal and human data are concordant with our findings of a mixed Th1/Th2 activation with implication of the CD8+ T cells in OA.

This profile could be specific of the low molecular weight agent used in these studies, namely isocyanates: OA is due to a large variety of allergens, among which high molecular weight allergens are frequently distinguished from low molecular weight allergens with regard to the induced pathology. Notably, the former are thought to induce a form of asthma similar to nonoccupational allergic asthma, in which atopy is a risk factor, specific IgEs are present in serum, and skin prick tests are relevant to the diagnosis. In OA related to low molecular weight agents, atopy is not a risk factor, specific IgEs are frequently not found, and thus skin prick tests are poorly contributive to the diagnosis (1). However the T-cell activation profile between both forms of substances involved was similar, which suggest that although IgE are not necessarily involved in both cases, some mechanisms are shared.

In addition, more and more publications indicate that in common non-OA, a Th1 activation accompanies the Th2 cytokine production (8). Indeed, whereas in some models of asthma the induction of Th1 cells was protective (19), in other cases, the presence of IFN-γ-producing cells exacerbated the asthmatic phenotype (20). In addition, in humans, a production of IFN-γ was found, correlated to asthma severity (21), symptoms (22), and bronchial hyper-responsiveness (23). It is noteworthy that IFN-γ-producing T cells in asthma were frequently CD8+ cells (23). This is in keeping with results found in ENA subjects. Indeed, whereas in these patients the SIT-induced Th2 activation was not found at the CD8+ level. In addition, a decrease of IFN-γ-producing T cells occurred, suggesting a crucial role for IFN-γ-producing T cells, notably CD8+, in the inception of asthma in exposed subjects.

This raises the question of the role of CD8+ cells in asthma. These cells are considered as a heterogeneous population, including effector cytotoxic T cells and cytokine-producing T cells but also NK cells, NKT cells, and γδ T cells. Furthermore, the bronchial infiltration by the CD8+ T cells was associated with the decline of FEV1 in asthma (24) and asthma mortality (25).

Therefore, the involvement of IFN-γ+ and of CD8+ cells in asthma could be a trait of increased severity. In this view, it is not surprising to find this trait in OA patients, as this form of asthma is considered as more severe than non-OA (1). No relationship was found between asthma severity or specific or nonspecific bronchial hyper-responsiveness and CD8+ or IFN-γ+ T cells in this study, probably because of the limited number of patients explored.

It was also recently pointed out that a deficiency in the Treg cell population could preclude to the mixed Th2/Th1 activation seen in asthma (26). Indeed, Treg cells regroup small populations of T cells, which constitutively produce immunosuppressive cytokines such as IL-10 and/or TGF-β. These cells are thought to be responsible for the immune homeostasis, preventing the organism from any unwarranted inflammation, notably against self-antigens and allergens (27). In this view, a deficiency in Treg cells could be responsible for the increase of auto-immune and allergic diseases observed in the last decades (28). A Treg cell deficiency was previously showed in asthma (8) and allergic rhinitis (12). The decrease of the Treg cells observed in OA patients after SIT, but overall the increase of Treg cells induced in ENA subjects are concordant with this hypothesis. The variation in the proportion of the Treg population was not previously investigated in OA after inhalation challenge. Hoffman and coll (29) assessed the Treg cells in blood after ingestion challenge in patients with OA, because of cereal flour exposure. In these conditions, they observed a decrease of CD4+CD25+ cells after ingestion but only when compared with placebo and not when comparing baseline to post-challenge data. A similar profile of mixed Th1/Th2 activation and a decrease of Treg cells were recently demonstrated in exacerbations of asthma, a condition that can be compared with allergen challenge (30).

T-cell activation has not been previously investigated in OR. These patients are rare; OR is frequently neglected and therefore unexplored. Herein, we demonstrate a T-cell activation profile reminiscent of what is described in non-occupational rhinitis. Indeed, as asthma, rhinitis is largely associated to a Th2 activation at baseline, enhanced under allergen stimulation (7). We found a deficient IFN-γ production in T cells at baseline, which is in keeping with an intrinsic Th2 skewing and a SIT-induced Th2 activation. This profile can be considered as different from the one seen in asthma, as Th1 activation and Treg cell decrease were not found in OR. However, it is more likely that the OR T-cell activation profile is intermediate, with an elevation of IFN-γ production and a decrease of Treg cells that do not reach significance in our study. Indeed, the mean cytokine and T-cell variation was concordant with OA results in a smaller extent.

In conclusion, our results demonstrate a gradient of T-cell activation from a tolerating profile in ENA subjects (decrease of Th1, increase of Th2 and Treg cells after SIT) to an inflammatory profile in OA (increase of both Th1 and Th2, decrease of Treg cells after SIT), with an intermediate stage in OR.

Acknowledgment

  1. Top of page
  2. Abstract
  3. Materials and methods
  4. Results
  5. Discussion
  6. Acknowledgment
  7. References

This work was supported by a grant from Comité National de Lutte contre Les Maladies Respiratoires, AP-HM.

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  2. Abstract
  3. Materials and methods
  4. Results
  5. Discussion
  6. Acknowledgment
  7. References
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