Diisocyanates are crucial ingredients in many important products and industries (i.e. construction, automotive, aerospace, medical, military/civilian). Recognized in 1951 as occupational allergens, progress in understanding diisocyanate asthma has lagged behind that of environmental asthma. Gaps in understanding diisocyanate asthma pathogenesis impede almost all aspects of disease control; exposure surveillance and prevention, disease screening and diagnosis, and prophylactic or post-exposure therapeutics or treatments. Differences between diisocyanate asthma and common environmental asthma are especially critical to screening and clinical workup, notably the lack of antigen (e.g. chemical)-specific IgE in affected workers. Individuals that continue to work with diisocyanates after developing “hypersensitivity” face long-term adverse pulmonary health outcomes, and in rare cases have died. In a prior R01 we developed a novel approach for delivering diisocyanate to the lower airways in mice (overcoming upper airway “scrubbing” that hampered prior studies) to help understand pathogenic responses and identify new exposure biomarkers useful for exposure surveillance. Our novel mouse diisocyanate asthma model has provided substantial insight into the immune responses triggered by exposure, particularly differences between pathogenic responses in immune sensitized hosts vs. non-pathogenic responses in non- sensitized hosts and differences in chemical (MDI) asthma vs. environmental asthma (see preliminary data). Importantly, the data highlight innate immune responses that differentiate “self” from “non-self” as a critical aspect of pathogenesis and identify candidate genes and molecular targets that mediate this process. The present investigation proposes to complete the elucidation of pathogenic mechanisms triggered by diisocyanate using our animal model and to translate promising preliminary findings in mice on biomarkers to clinical samples from exposed workers. We hypothesize that we can utilize our mouse model of diisocyanate asthma, taking advantage of genetic manipulation and experimental drugs that focus on specific molecular targets, to better understand the mechanisms that differentiate pathogenic from non-pathogenic responses. We further hypothesize that exposure biomarkers from animal studies, including di-lysine-diisocyanate recently discovered by our laboratory, can translate to humans and serve as an effective basis for biomonitoring workplace exposures. The Specific Aims are: Aim 1. Identify and characterize the dendritic cell(s) that initiates pathologic systemic immune sensitization to diisocyanate. Aim 2. Identify and characterize the effector cells and molecules in the lungs that mediate asthma pathology following respiratory tract exposure. Aim 3. Identify, validate, and translate biomarkers of diisocyanate exposure and sensitivity/disease. The application is relevant to Construction, Manufacturing, and Transportation NORA sectors ...