Multiple challenges in a mouse model of chemical-induced asthma lead to tolerance: ventilatory and inflammatory responses are blunted, immunologic humoral responses are not

Evidential requirements for the regulatory hazard and risk assessment of respiratory sensitisers: methyl methacrylate as an example

This review addresses the need for a framework to increase the consistency, objectivity and transparency in the regulatory assessment of respiratory sensitisers and associated uncertainties. Principal issues are considered and illustrated through a case study (with methyl methacrylate). In the absence of test methods validated for regulatory use, formal documentation of the weight-of-evidence for hazard classification both at the level of integration of individual studies within lines of evidence and across a broad range of data streams was agreed to be critical for such a framework. An integrated approach is proposed to include not only occupational studies and clinical evidence for the regulatory assessment of respiratory sensitisers, but also information on structure and physical and chemical factors, predictive approaches such as structure activity analysis and in vitro and in vivo mechanistic and toxicokinetic findings. A weight-of-evidence protocol, incorporating integration of these sources of data based on predefined considerations, would contribute to transparency and consistency in the outcome of the assessment. In those cases where a decision may need to be taken on the basis of occupational findings alone, conclusions should be based on transparent weighting of relevant data on the observed prevalence of occupational asthma in various studies taking into account all relevant information including the range and nature of workplace exposures to the substance of interest, co-exposure to other chemicals and study quality.

Strain-Specific Differences in House Dust Mite (Dermatophagoides farinae)-Induced Mouse Models of Allergic Rhinitis

Objectives.

Limited information is available regarding strain-related differences in mouse models of allergic rhinitis induced by Dermatophagoides farinae (Der f1). In this study, we compared differences between two mouse strains and determined the optimal dose of Der f1 for allergic rhinitis mouse models.

Methods.

Forty-eight mice were assigned to the following six groups (n=8 per group): group A (control, BALB/c), group B (Der f1-sensitized BALB/c, 25 µg), group C (Der f1-sensitized BALB/c, 100 µg), group D (control, C57BL/6), group E (Der f1-sensitized C57BL/6, 25 µg), and group F (Der f1-sensitized C57BL/6, 100 µg). Allergic inflammation was induced with Der f1 and alum sensitization, followed by an intranasal challenge with Der f1. Rubbing and sneezing scores, eosinophil and neutrophil infiltration, and immunoglobulin, cytokine, and chemokine levels in the nasal mucosa and from splenocyte cultures were assessed.

Results.

Rubbing and sneezing scores were higher in groups B, C, E, and F than in groups A and D, with a similar pattern in both strains (i.e., group B vs. E and group C vs. F). Serum immunoglobulin levels were significantly elevated compared to the control in groups B and C, but not in groups E and F. Eosinophil and neutrophil infiltration increased (all P<0.05) after the Der f1 challenge (groups B, C, E, and F) compared to the control (groups A and D) in both the BALB/c and C57BL/6 strains, without any significant difference between the two strains (group A vs. D, group B vs. E, and group C vs. F) (P>0.05). BALB/c mice (group B) showed a greater elevation of splenic interleukin (IL)-4 (P<0.01), IL-5 (P<0.01), and IL-6 levels (P<0.05) and nasal IL-4 mRNA levels (P<0.001) than the C57BL/6 mice (group E). Interestingly, mice treated with 100 µg Der f1 showed a weaker allergic response than those treated with 25 µg.

Conclusion.

We found 25 µg to be a more appropriate dose for Der f1 sensitization. BALB/c mice are more biased toward a Th2 response and are a more suitable model for allergic rhinitis than C57BL/6 mice. This study provides information on the appropriate choice of a mouse model for allergic rhinitis.

Clinical efficacy of recombinant human latrophilin 3 antibody in the treatment of pediatric asthma

Pediatric asthma is a chronic pulmonary inflammatory disease featuring hypersecretion of mucus and inflammation in the airway, resulting in dysfunction of the airway smooth muscle. Previous evidence demonstrated that latrophilins, a novel family of receptors, present a beneficial effect on airway smooth muscle cells. In the present study, the therapeutic effects of recombinant human latrophilin 3 (rhLPHN3) antibody (Ab) in patients with pediatric asthma were investigated, and the molecular mechanism underlying the function of LPHN3 in the treatment of asthma in clinical practice was examined. A total of 342 pediatric asthma cases were recruited and randomly divided into three groups, receiving treatment with rhLPHN3 Ab (n=134), salbutamol (n=108) or montelukast (n=100) by nasal aerosolization. Each group received the respective clinically tested dose for 16 weeks. Inflammatory factors interleukin (IL)-10, IL-17, IL-4, matrix metallopeptidase-9 (MMP-9), interferon-γ (IFN-γ) and transforming growth factor-β (TGF-β) levels in peripheral blood mononuclear cells were analyzed prior to and post treatment. The clinical outcomes revealed that pathological alterations were significantly improved following treatment with rhLPHN3 Ab for patients with pediatric asthma when compared with those receiving salbutamol and montelukast. It was also observed that rhLPHN3 Ab downregulated the plasma concentration levels of IL-10, IL-17, IL-4 and MMP-9, and upregulated IFN-γ and TGF-β levels in the three groups. In addition, clinical data demonstrated that rhLPHN3 Ab significantly promoted E-selectin and mucin 5AC expression, as well as improved the activation of nuclear factor (NF)-κB p65 DNA binding activity and the phosphorylation levels of protein kinase A. Furthermore, rhLPHN3 Ab markedly improved adhesion and proliferation of airway smooth muscle cells, which led to promotion of the contraction of these cells. In conclusion, these clinical data suggest that rhLPHN3 Ab serves an important role in the inhibition of inflammatory mediators through downregulation of NF-κB signaling pathway, which contributes to airway remodeling and bronchodilation in patients with pediatric asthma.

Vitamin E effect in a rat model of toluene diisocyanate-induced asthma

Background and aim

The aim of the study was to evaluate vitamin E effect upon oxidative stress associated with toluene −2, 4-diisocyanate (TDI)-induced asthma in rats.

Methods

The five study groups were: control, vehicle, TDI, vehicle+E, TDI+E. TDI animals were sensitized by nasal administration of TDI 10% (5μl/nostril) between days 1–7 and 15–21. Between days 22–28 groups TDI+E and vehicle+E rats received vitamin E (50 mg/kg, i. v.), and control, vehicle and TDI groups received saline solution. On day 29 the rats were challenged by intranasal application of 5% TDI (5 μl/nostril). On day 30 blood, BALF and lung biopsy were harvested. Oxidative stress tests were malondialdehyde (MDA), protein carbonyls (PC), total thiols (tSH), 1,1-diphenyl-2-picryl hydrazyl (DPPH) and reduced glutathione (GSH).

Results

TDI sensitization increased oxidative stress systemically, but also locally in the respiratory airways and lung tissue. There was an increase of MDA and PC formation associated with a deficiency of the antioxidant defense reflected by DPPH decreases. There were no differences between systemic and local lung concentrations of oxidized molecules.

After vitamin E treatment oxidative stress was reduced mostly due to serum, BALF and lung tissue GSH and DPPH increase.

Conclusion

The study showed that in rat TDI-induced asthma there was oxidative stress caused by increased ROS production and antioxidants deficiency, and vitamin E reduced ROS production and improved antioxidant defense.

Development of a respiratory sensitization/elicitation protocol of toluene diisocyanate (TDI) in Brown Norway rats to derive an elicitation-based occupational exposure level

Toluene diisocyanate (TDI), a known human asthmagen, was investigated in skin-sensitized Brown Norway rats for its concentration×time (C×t)-response relationship on elicitation-based endpoints. The major goal of study was to determine the elicitation inhalation threshold dose in sensitized, re-challenged Brown Norway rats, including the associated variables affecting the dosimetry of inhaled TDI-vapor in rats and as to how these differences can be translated to humans. Attempts were made to duplicate at least some traits of human asthma by using skin-sensitized rats which were subjected to single or multiple inhalation-escalation challenge exposures. Two types of dose-escalation protocols were used to determine the elicitation-threshold C×t; one used a variable C (Cvar) and constant t (tconst), the other a constant C (Cconst) and variable t (tvar). The selection of the "minimal irritant" C was based an ancillary pre-studies. Neutrophilic granulocytes (PMNs) in bronchoalveolar lavage fluid (BAL) were considered as the endpoint of choice to integrate the allergic pulmonary inflammation. These were supplemented by physiological measurements characterizing nocturnal asthma-like responses and increased nitric oxide in exhaled breath (eNO). The Cconst×tvar regimen yielded the most conclusive dose-response relationship as long C was high enough to overcome the scrubbing capacity of the upper airways. Based on ancillary pre-studies in naïve rats, the related human-equivalent respiratory tract irritant threshold concentration was estimated to be 0.09ppm. The respective 8-h time-adjusted asthma-related human-equivalent threshold C×t-product (dose), in 'asthmatic' rats, was estimated to be 0.003ppm. Both thresholds are in agreement of the current ACGIH TLV(®) of TDI and published human evidence. In summary, the findings from this animal model suggest that TDI-induced respiratory allergy is likely to be contingent on two interlinked, sequentially occurring mechanisms: first, dermal sensitizing encounters high enough to cause systemic sensitization. Second, when followed by inhalation exposure(s) high enough to initiate and amplify an allergic airway inflammation, then a progression into asthma may occur. This bioassay requires an in-depth knowledge on respiratory tract dosimetry and irritation of the involved test substance to clearly understand the dosimetry causing C- and/or C×t-dependent respiratory tract irritation and eventually asthma.

IL-4 and IL-5 secretions predominate in the airways of wistar rats exposed to toluene diisocyanate vapor

OBJECTIVES

We established a Wistar rat model of asthma caused by toluene diisocyanate (TDI) exposure, and investigated the relationship between TDI exposure concentrations and respiratory hypersensitivity, airway inflammation, and cytokine secretions in animals, to better understand the mechanism of TDI induced occupational asthma.

METHODS

Wistar rats were exposed to two different concentrations of TDI vapor four hours a day for five consecutive days. Bronchoalveolar lavage (BAL) was performed, and differential leucocytes from the BAL fluid were analyzed. Lung histopathological examination was carried out to investigate the inflammatory status in the airways. Production of cytokines interleukin (IL)-4 and IL-5 productions in the BAL fluid in vivo was determined with enzyme-linked immunosorbent assay kits.

RESULTS

The TDI-exposed rats exhibited greater airway hypersensitivity symptoms than the control rats. The BAL differential cell count and lung histopathological examination demonstrated that inflammation reactions were present in both the central and peripheral airways, characterized with marked infiltration of eosinophils in the TDI-exposed rats. The cytokine assay showed that IL-4 and IL-5 were predominantly produced in the BAL fluid in vivo.

CONCLUSIONS

These findings imply that TDI exposure concentrations may greatly affect the occurrence and extent of inflammatory events and that Th2 type cytokines may play an important role in the immunopathogenesis of TDI-induced occupational respiratory hypersensitivity.

B-lymphocytes as key players in chemical-induced asthma

T-lymphocytes and B-lymphocytes are key players in allergic asthma, with B-lymphocytes producing antigen-specific immunoglobulins E (IgE). We used a mouse model of chemical-induced asthma and transferred B-lymphocytes from sensitized animals into naïve wild type mice, B-lymphocyte knock-out (B-KO) mice or severe combined immunodeficiency (SCID) mice. On days 1 and 8, BALB/c mice were dermally sensitized with 0.3% toluene diisocyanate (TDI) (20µl/ear). On day 15, mice were euthanized and the auricular lymph nodes isolated. B-lymphocytes (CD19⁺) were separated from the whole cell suspension and 175,000 cells were injected in the tail vein of naïve wild type, B-KO or SCID mice. Three days later, the mice received a single oropharyngeal challenge with 0.01% TDI (20µl) or vehicle (acetone/olive oil (AOO)) (controls). Airway reactivity to methacholine and total and differential cell counts in the bronchoalveolar lavage (BAL) fluid were measured 24 hours after challenge. B-lymphocytes of AOO or TDI-sensitized mice were characterized for the expression of surface markers and production of cytokines. We found that transfer of B-cells obtained from mice dermally sensitized to toluene diisocyanate (TDI) into naïve wild type mice, B-KO mice or SCID mice led, within three days, to an acute asthma-like phenotype after an airway challenge with TDI. This response was specific and independent of IgE. These B-lymphocytes showed antigen presenting capacities (CD80/CD86 and CD40) and consisted of B effector (Be)2- (IL-4) and Be1-lymphocytes (IFN-γ). The transferred B-lymphocytes were visualized near large airways, 24 hours after TDI challenge. Thus, B-lymphocytes can provoke an asthmatic response without the action of T-lymphocytes and without major involvement of IgE.

Re-challenge with ovalbumin failed to induce bronchial asthma in mice with eosinophilic bronchitis

OBJECTIVE

To investigate whether eosinophilic bronchitis without airway hyperresponsiveness will develop bronchial asthma in allergic mice.

METHODS

Mice were sensitized with OVA on days 0, 7, and 14, challenged on days 21 to 23 (1(st) OVA challenge), and re-challenged on days 46 to 48 (2(nd) OVA challenge), intranasally with 10 (the EB group) and 200 (the AS group) μg OVA. Lung resistance (RL) was assessed 24 h after each challenge and on day 45 followed by analysis of leukocyte distribution in the bronchoalveolar lavage (BAL) fluid and histological examination.

RESULTS

Twenty-four hours after the 1(st) OVA challenge, aerosolized methacholine caused a dose-dependent increase in RL in all groups. At doses ≥1.56 mg/mL, RL in the AS group was significantly higher than that of the NS-1 group (P<0.01 or 0.05) and at doses ≥12.5 mg/mL, RL was markedly higher in the AS group than that of the EB group (P<0.01). The percentage of eosinophils in both the EB group and the AS group was markedly higher than that of the control group. Twenty-four hours after the 2(nd) OVA challenge, at doses ≤12.5 mg/mL, there was no significant difference in RL among all groups (P>0.05). At doses ≥12.5 mg/mL, RL in the AS group was significantly higher than that of the control group and EB group (P<0.01 or 0.05). The percentage of eosinophils in the AS group was noticeably higher than that of the EB group(P<0.05). Furthermore, there was apparent infiltration by inflammatory cells, predominantly eosinophils, into the sub-epithelial region of the bronchus and the bronchioles and around the vessels in the EB and AS group.

CONCLUSION

Re-challenge with low doses of ovalbumin did not increase airway reactivity and failed to induce bronchial asthma in mice with ovalbumin-induced EB.

Effect of inhaled toluene diisocyanate on local immune response based on murine model for occupational asthma

Highly reactive, low-molecular-weight diisocyanates (DIC) are the most commonly identified cause of occupational asthma (OA). Animal/clinical studies of DIC asthma have been more limited compared with atopic asthma, and an understanding of DIC pathogenesis is less clear. The aim of this study was to investigate in a mouse model, toluene diisocyanate (TDI, as 2,4-TDI isomer)-induced inflammatory reactions/cytokine profile changes in the lungs and accompanying changes in lymph node lymphocyte sub-populations. The study used female BALB/cJ/Han/IMP mice that were exposed first intra-nasally and then in an inhalation chamber to TDI or air. After the final exposure, bronchoalveolar lavage fluid (BALF) was collected and changes induced in inflammatory cell composition, levels of key cytokines (i.e. IL-4, TNFα, IFNγ), and lymphocyte sub-population profiles within auricular lymph nodes, were evaluated. Total number of cells in the BALF of treated mice was significantly higher than in control mice BALF. There was also a significant increase in BALF neutrophil and eosinophil levels with TDI mice compared to in controls; lymphocyte and macrophage numbers did not significantly differ. A significant increase in BALF levels of TNFα and IFNγ was also noted in mice exposed to TDI relative to levels in controls. BALF IL-4 levels were also increased, but the change from control was not significant. Lastly, the levels/percentages of CD3(+)CD4(+) (T-helper [TH]) lymphocytes significantly increased in the lymph nodes of TDI-exposed groups while those of the CD3(+)CD8(+) cells decreased as compared to in control mice. These studies, the first to assess TDI-induced changes in levels of three key cytokines in BALF in conjunction with changes in local lymph nodes following first an intra-nasal and then a general inhalation exposure to a low-level of TDI, confirm that TDI inhalation induces a pathology manifested by airway inflammation, TH cell-derived cytokine production, and shifts in lymph node lymphocytes sub-populations toward increases in TH cells.

Immune sensitization to methylene diphenyl diisocyanate (MDI) resulting from skin exposure: albumin as a carrier protein connecting skin exposure to subsequent respiratory responses

BACKGROUND

Methylene diphenyl diisocyanate (MDI), a reactive chemical used for commercial polyurethane production, is a well-recognized cause of occupational asthma. The major focus of disease prevention efforts to date has been respiratory tract exposure; however, skin exposure may also be an important route for inducing immune sensitization, which may promote subsequent airway inflammatory responses. We developed a murine model to investigate pathogenic mechanisms by which MDI skin exposure might promote subsequent immune responses, including respiratory tract inflammation.

METHODS

Mice exposed via the skin to varying doses (0.1-10% w/v) of MDI diluted in acetone/olive oil were subsequently evaluated for MDI immune sensitization. Serum levels of MDI-specific IgG and IgE were measured by enzyme-linked immunosorbant assay (ELISA), while respiratory tract inflammation, induced by intranasal delivery of MDI-mouse albumin conjugates, was evaluated based on bronchoalveolar lavage (BAL). Autologous serum IgG from "skin only" exposed mice was used to detect and guide the purification/identification of skin proteins antigenically modified by MDI exposure in vivo.

RESULTS

Skin exposure to MDI resulted in specific antibody production and promoted subsequent respiratory tract inflammation in animals challenged intranasally with MDI-mouse albumin conjugates. The degree of (secondary) respiratory tract inflammation and eosinophilia depended upon the (primary) skin exposure dose, and was maximal in mice exposed to 1% MDI, but paradoxically limited in mice receiving 10-fold higher doses (e.g. 10% MDI). The major antigenically-modified protein at the local MDI skin exposure site was identified as albumin, and demonstrated biophysical changes consistent with MDI conjugation.

CONCLUSIONS

MDI skin exposure can induce MDI-specific immune sensitivity and promote subsequent respiratory tract inflammatory responses and thus, may play an important role in MDI asthma pathogenesis. MDI conjugation and antigenic modification of albumin at local (skin/respiratory tract) exposure sites may represent the common antigenic link connecting skin exposure to subsequent respiratory tract inflammation.

Proteome analysis of multiple compartments in a mouse model of chemical-induced asthma

Occupational asthma is the principal cause of work-related respiratory disease in the industrial world. Toluene-2,4-diisocyanate (TDI) is one of the most common respiratory sensitizers leading to occupational asthma. Using a mouse model of chemical-induced asthma, we explored proteome changes in multiple compartments of mice sensitized and challenged with TDI or acetone-olive oil (AOO; vehicle). Airway reactivity to methacholine and a bronchoalveolar lavage (BAL) cell count was assessed in treated and control mice, 1 day after challenge. Subsequently, two-dimensional differential gel electrophoresis (2D-DIGE) was performed on auricular lymph nodes, BAL, and serum comparing TDI-treated and vehicle-treated control mice. The differentially expressed proteins were identified by mass spectrometry and pathway analysis was performed. TDI-treated mice exhibit increased airway reactivity (2.6-fold increase) and a neutrophilic inflammation in the BAL fluid, compared to control mice. 2D-DIGE showed 53, 210, and 40 differentially expressed proteins in the auricular lymph nodes, BAL, and serum of TDI-treated versus vehicle-treated mice, respectively. Several of the identified proteins could be linked with inflammation, neutrophil chemotaxis, and/or oxidative stress. Physiologic and immunologic readouts of the asthmatic phenotype, such as inflammation, were confirmed in three compartments by several of the differentially expressed proteins via 2D-DIGE and computerized pathway analysis.

Successful transfer of chemical-induced asthma by adoptive transfer of low amounts of lymphocytes in a mouse model

BACKGROUND

We optimized an adoptive transfer protocol in our mouse model of TDI-induced asthma in order to investigate the mechanisms of this type of occupational asthma.

METHODS

On days 1 and 8, BALB/c mice were dermally sensitized with 0.3% TDI or vehicle (acetone/olive oil), and on day 15, they were sacrificed and a cell suspension was made from auricular lymph nodes. First, 0.1 x 10⁶, 0.5 x 10⁶, 1 x 10⁶ or 5 x 10⁶ cells were injected intravenously into naïve mice and three days later these mice received an oropharyngeal challenge with 0.01% TDI or vehicle. Second, mice were challenged with 0.01% TDI 1, 3, 5 or 7 days after transferring 0.5 x 10⁶ cells. The following endpoints were measured one day after challenge: methacholine reactivity; differential cell counts in bronchoalveolar lavage (BAL) and total serum IgE.

RESULTS

Naïve mice receiving 0.5 x 10⁶, 1 x 10⁶ or 5 x 10⁶ cells showed significant increases in airway reactivity one day after TDI challenge; BAL neutrophils were increased after transferring 0.5 x 10⁶ and 1 x 10⁶ cells. A TDI challenge 3 days after transferring 0.5 x 10⁶ cells gave a 3-fold increase in airway resistance and a pronounced airway inflammation, whereas challenging at other time points gave no differences.

CONCLUSION

We were able to passively sensitize naïve mice using lymph node cells from TDI-sensitized mice, resulting in an asthma-like response after an airway challenge. In comparison to other adoptive transfer protocols we used substantially lower number of cells to obtain the desired response.

Choice of mouse strain influences the outcome in a mouse model of chemical-induced asthma

Background

The development of occupational asthma is the result of interactions between environmental factors and individual susceptibility. We assessed how our model of chemical-induced asthma is influenced by using different mouse strains.

Methodology/Principal Findings

On days 1 and 8, male mice of 7 different strains (BALB/c, BP/2, A/J, C57Bl/6, DBA/2, CBA and AKR) were dermally treated with toluene-2,4-diisocyanate (TDI) (0.3%) or vehicle (acetone/olive oil, AOO, 2∶3) on each ear (20 µl). On day 15, they received an oropharyngeal instillation of TDI (0.01%) or AOO (1∶4). Airway reactivity to methacholine, total and differential cell counts in bronchoalveolar lavage (BAL) and total serum IgE and IgG_2a levels were measured. Lymphocyte subpopulations in auricular lymph nodes and in vitro release of cytokines by ConA stimulated lymphocytes were assessed. In TDI-sensitized and challenged mice, airway hyper-reactivity was only observed in BALB/c, BP/2, A/J and AKR mice; airway inflammation was most pronounced in BALB/c mice; numbers of T-helper (CD4⁺), T-activated (CD4⁺CD25⁺), T-cytotoxic (CD8⁺) and B- lymphocytes (CD19⁺) were increased in the auricular lymph nodes of BALB/c, BP/2, A/J and CBA mice; elevated concentrations of IL-4, IL-10, IL-13 and IFN-γ were detected in supernatant of lymphocytes from BALB/c, BP/2, A/J, C57Bl/6 and CBA mice cultured with concanavaline A, along with an increase in total serum IgE.

Conclusion

The used mouse strain has considerable and variable impacts on different aspects of the asthma phenotype. The human phenotypical characteristics of chemically-induced occupational asthma were best reproduced in Th2-biased mice and in particular in BALB/c mice.

Malignant cells fuel tumor growth by educating infiltrating leukocytes to produce the mitogen Gas6

The transforming and tumor growth-promoting properties of Axl, a member of the Tyro3, Axl, and Mer (TAM) family of receptor tyrosine kinases (TAMRs), are well recognized. In contrast, little is known about the role of the TAMR ligand growth arrest-specific gene 6 (Gas6) in tumor biology. By using Gas6-deficient (Gas6(-/-)) mice, we show that bone marrow-derived Gas6 promotes growth and metastasis in different experimental cancer models, including one resistant to vascular endothelial growth factor inhibitors. Mechanistic studies reveal that circulating leukocytes produce minimal Gas6. However, once infiltrated in the tumor, leukocytes up-regulate Gas6, which is mitogenic for tumor cells. Consistent herewith, impaired tumor growth in Gas6(-/-) mice is rescued by transplantation of wild-type bone marrow and, conversely, mimicked by transplantation of Gas6(-/-) bone marrow into wild-type hosts. These findings highlight a novel role for Gas6 in a positive amplification loop, whereby tumors promote their growth by educating infiltrating leukocytes to up-regulate the production of the mitogen Gas6. Hence, inhibition of Gas6 might offer novel opportunities for the treatment of cancer.

Immunological determinants in a mouse model of chemical-induced asthma after multiple exposures

In a mouse model of chemical-induced asthma, we investigated the effects of multiple challenges, using toluene diisocyanate (TDI), a known cause of occupational asthma. On days 1 and 7, BALB/c mice received TDI or vehicle (acetone/olive oil). On days 10, 13 and 16 the mice received an intranasal instillation of TDI. Ventilatory function (Penh) was monitored by whole body plethysmography for 40 min after each challenge. Reactivity to methacholine was measured 22 h later. Pulmonary inflammation, TNF-alpha and MIP-2 levels were assessed 24 h after the last challenge by broncho-alveolar lavage (BAL). Other immunological parameters included total IgE, lymphocyte sub-populations in auricular and cervical lymph nodes, and IL-4, IFN-gamma and IL-13 levels in supernatants of lymph node cells, cultured with or without concanavalin A. Early ventilatory function and airway reactivity increased in all groups that received a dermal application and one or multiple intranasal challenges of TDI. After multiple challenges, lung inflammation was characterized by neutrophils (approximately 15%), and eosinophils (approximately 4%), along with an increase in BAL MIP-2 and TNF-alpha levels. The auricular and cervical lymph node cells of all sensitized mice showed an increase in B cells, Th cells and an increased concentration of in vitro release of IL-4, IFN-gamma and IL-13 after stimulation with concanavalin A. Total serum IgE was elevated in dermally TDI-sensitized mice. This protocol including multiple challenges results in a model that resembles human asthma, indicating that responses found in the model using a single challenge could be a good first indication for the development of asthma.

Is toluene diamine a sensitizer and is there cross-reactivity between toluene diamine and toluene diisocyanate?

Toluene diamine (TDA) is formed when toluene diisocyanate (TDI), a potent sensitizer, comes in contact with an aqueous environment. The sensitizing capacity of TDA and the cross-reactivity between TDI and TDA are unknown. TDA (5-25%) and TDI (0.3%), dissolved in acetone/olive oil (AOO) (4:1) were tested in the mouse local lymph node assay (LLNA). To determine the capacity of TDA to elicit an asthmatic response and to determine the cross-reaction with TDI, a locally developed experimental mouse model of chemical-induced asthma was used. On days 1 and 8, BALB/c mice received 20 microl of TDI (0.3%), TDA (20%), or AOO (4:1) on each ear. On day 15, they received an intranasal instillation of TDI (0.1%), TDA (0.5%) or AOO (3:2). The EC(3) of TDA in the LLNA is 19%. In the model of chemical-induced asthma, TDI induced a ventilatory response [increased Penh after challenge; increased airway hyperreactivity (AHR)], inflammatory changes (bronchoalveolar lavage neutrophils), and immunological changes (increased CD19(+) lymphocytes, IL-4 and total serum IgE), whereas TDA did not show any of these responses. Mice sensitized with TDI and challenged with TDA also did not show any airway or inflammatory response, although they had increased levels of total serum IgE. Mice sensitized with TDA and challenged with TDI did not show any response. According to the classification of sensitizers in the LLNA, TDA is a weak dermal sensitizer. In the experimental mouse model of chemical-induced asthma, TDA does not act as a respiratory sensitizer, at the concentration used. No cross-reactivity between TDI and TDA was found.