Search

Background The bioreactivity of isocyanate, a leading cause of occupational asthma, has led to uncertainty regarding the chemical's antigenicity and mechanisms that elicit immunopathology. Objective To understand better the biologically relevant antigenic forms of hexamethylene diisocyanate (HDI), commonly used in the auto body industry. Methods Human albumin was exposed to HDI vapors through a novel approach designed to model the air–liquid interface of the human airway. Vapor HDI-exposed albumin was characterized by electrophoresis, chemical substitution analysis, mass spectrometry, and serology studies on auto body shop workers (N = 203) and HDI asthmatics (N = 11). Results HDI vapors caused significant changes in the shape and/or charge of human albumin, which differed from albumin exposed to liquid phase HDI, with lower isocyanate substitution ratios and distinct electrophoretic mobility. Specific sites of vapor HDI conjugation to albumin were identified at His 247 and Lys 414 . Vapor HDI-exposed albumin was specifically recognized by the humoral arm of the human immune system, with a strong dependence on albumin as the carrier. Vapor HDI-exposed albumin-specific IgG titers were significantly associated with HDI exposure ( P = .001), and specific IgE was detectable in 55% (6/11) of isocyanate asthmatics versus 1.5% (3/203) of exposed healthy workers. Parallel studies using HDI-exposed albumin conjugates produced by previously published methods showed less significant associations of HDI-specific IgG and IgE with exposure and disease, respectively. Conclusion HDI-albumin conjugates produced by novel vapor phase exposure methods may be more physiologically relevant than those produced by previously published methods and of greater utility in characterizing the immune responses associated with HDI exposure and asthma.

The human immune response to isocyanate, a leading cause of occupational asthma, remains incompletely characterized, including the cell types involved and the form of the chemical that acts as an antigen.The purpose of this investigation was to characterize human T cells that respond to hexamethylene diisocyanate (HDI), an aliphatic isocyanate routinely used in the automobile body industry.Human T-cell lines were generated and characterized from peripheral blood of HDI-exposed and HDI-unexposed subjects, using two different HDI antigens, HDI-conjugated albumin and HDI-exposed human airway epithelial cells (NCI-H292). Flow cytometry was used to characterize the phenotype of HDI-responsive T cells. ELISA and intracellular staining techniques were used to evaluate HDI-induced cytokine production. DNA sequence analysis of T-cell receptors was used to further define clonal populations of HDI-responsive T cells.HDI antigen preparations but not "mock exposed" control antigens lead to increased proliferation of specific cell types, CD3+CD4-CD8(dim) and/or CD3+CD4-CD8- cells, from HDI-exposed but not from HDI-unexposed subjects. These HDI-responsive T cells expressed unique oligoclonal gamma/delta rather than alpha/beta T-cell receptors, with characteristics suggestive of antigen-mediated selection and specificity. The HDI-stimulated gamma/delta T cells were associated with T(H)1-like cytokines and produce IFN-gamma but not IL-5 or IL-13.These data are the first to demonstrate that HDI can selectively stimulate gamma/delta T cells with the potential to modulate the human immune response to exposure.

Background: Exposure to diisocyanates, a group of highly reactive, low-molecular-weight compounds, is a major cause of occupational asthma. In contrast to mouse models of atopic asthma, previous mouse models of diisocyanate-induced asthma have failed to show lung inflammation with characteristics of human disease. Objective : Our goal was to establish a novel mouse model of diisocyanate-induced asthma in which lung inflammation reminiscent of that seen in human asthma is generated after inhaled antigen challenge. Methods : BALB/c mice were epicutaneously sensitized to hexamethylene diisocyanate (HDI) and then challenged with an HDI-protein conjugate administered by means of an intranasal droplet. Results : HDI sensitization resulted in development of contact hypersensitivity and HDI-specific antibody production. Most importantly, however, vigorous inflammatory responses with characteristics of human asthma were generated in the lung after inhaled HDI challenge. Challenge of sensitized, but not unsensitized, mice resulted in airway eosinophilia, mucus hypersecretion, and production of T H 1-type (IFN-γ) and T H 2-type (IL-4, IL-5, and IL-13) cytokines by lung inflammatory cells. Despite the mixed T H 1/T H 2 response induced by HDI sensitization, use of cytokine-deficient mice revealed that airway eosinophilia was mediated by T H 2 cytokines and not by IFN-γ. Conclusion : We report a novel mouse model of diisocyanate-induced asthma that, in contrast to previous models, demonstrates antigen-induced lung inflammation with characteristics of human disease. This model will allow investigation of the immunopathogenesis of diisocyanate-induced asthma and should provide insight into this common form of occupational disease. (J Allergy Clin Immunol 2002;109:873–8.)

Background: Isocyanates are a group of highly reactive cross-linking chemicals that cause airway inflammation and asthma in exposed individuals. Isocyanates have been detected along the airway epithelia of exposed workers and animals, prompting the hypothesis that isocyanates can directly bind to epithelial cell proteins. Objective: We tested the hypothesis that hexamethylene diisocyanate (HDI) binds directly to lung epithelial cell proteins and initiated studies to evaluate the immunostimulatory potential of HDI-conjugated lung epithelial cell proteins. Methods: Human lung epithelial cell lines were exposed to vapor- and liquid-phase HDI, and the cellular proteins were analyzed for HDI conjugation by Western blotting and tested for the ability to induce lymphocyte proliferation in vitro. Results: A number of epithelial cell polypeptides, ranging from 25 to 110 kd in apparent molecular weight, were conjugated with HDI after exposure of the human lung epithelial cell lines (A549 and NCI-H292) to HDI concentrations greater than 0.005% (vol/vol) in the liquid phase. Vapor-phase HDI exposure resulted in a more restricted HDI conjugation pattern, with major HDI-conjugated polypeptides migrating at 47, 71, and 91 kd. HDI-conjugated epithelial cell proteins specifically stimulated proliferation of PBMCs from subjects with isocyanate-induced asthma but not HDI-exposed nonasthmatic individuals or atopic subjects with nonisocyanate-related asthma. Conclusions: The data demonstrate that epithelial cell proteins readily react with HDI and that HDI-conjugated epithelial cell proteins can stimulate lymphocyte proliferation. Further characterization and evaluation of HDI-conjugated epithelial cell proteins will elucidate their potential role in the pathogenesis of isocyanate-induced asthma. (J Allergy Clin Immunol 1999;104:341-7.)