Key Event Title
|Level of Biological Organization|
Key Event Components
Key Event Overview
AOPs Including This Key Event
|AOP Name||Role of event in AOP|
|Covalent binding to proteins leads to Respiratory Sensitisation/Sensitization/Allergy||AdverseOutcome|
|All life stages|
Key Event Description
The development of an allergic hypersensitivity reaction in the respiratory tract is a two-step process, first requiring induction of the immune response, here as a result of exposure to a low-molecular-weight chemical (Boverhof et al, 2008). Subsequent single or multiple exposures to the same substance result in elicitation of an allergic hypersensitivity reaction, characterized by breathlessness and wheezing, airflow obstruction, bronchoconstriction, and tightness of the chest (Lauenstein et al, 2014). Reactions can be acutely life threatening or lead to chronic occupational asthma (Boverhof et al, 2008).
How It Is Measured or Detected
Clinical signs described above can be objectively assessed in humans to confirm diagnosis of respiratory hypersensitivity.
Boverhof et al (2008) reviews various in vivo methods to detect respiratory hypersensitivity.
In rats, respiratory exposure to diisocyanites leads to immediate and delayed airway response (i.e. lung function). Elicitation is confirmed measuring PMN in bronchoalveolar lavage fluid (BAL) one day after inhalation challenge and exhaled NO (Pauluhn 2014).
In mice, induction of immune response, measured by T-lymphocyte maturation and proliferation in local lymph nodes, can often be detected using a Local Lymph Node Assay protocol (OECD 2010) with subsequent cytokine fingerprinting or IgE testing (Dearman et al 2003; Boverhof et al 2008).
Allergen-specific IgE detection and measurement techniques include skin tests (intradermal and subcutaneous skin prick testing) and blood testing using immune assays such as ELISAs and commercially available tests such as ImmunoCAP™. For example, Bernstein et al. investigated the ability of TMA skin testing to identify sensitized workers and found that skin prick testing was positive in 8 of 11 workers with serum-specific IgE and intradermal testing in a further two. (Bernstein et al., 2011) It is important to note, however, that there are technical challenges associated with detection and measurement of specific IgE and IgG to chemical respiratory allergens, including production of the correct protein conjugate and timing of measurement. (Kimber et al., 2014, Quirce, 2014) Immune assays such as ELISA or ImmunoCAP are also used to investigate allergen-specific antibody isotype profiles. (Movérare et al., 2017) Investigations into direct and indirect class switching involve transcriptomic analyses of IgE heavy chain transcripts and are challenging due to the scarcity of IgE-switched B cells in human blood. (Davies et al., 2013)
Domain of Applicability
Regulatory Significance of the Adverse Outcome
This adverse outcome is of high regulatory interest and relevance, though no test guideline is available. Regulatory agencies and industrial producers are interested in preventing the first step--induction of immune response. Importantly, induction of respiratory sensitisation can be obtained via skin exposure, which is consequential for potential exposure restrictions.
Boverhof DR, Billington R, Bhaskar Gollapudi B, Hotchkiss JA, Krieger SM, Poole A, Wiescinski CM, and Woolhiser MR. 2008. Respiratory sensitization and allergy: Current research approaches and needs. Tox Appl Pharm 226:1-13.
Dearman RJ, Betts CJ, Humphreys N, Flanagan BF, Gilmour NJ, Basketter DA, Kimber I. 2003. Chemical allergy: considerations for the practical application of cytokine profiling. Toxicol. Sci. 71, 137–145.
Lauenstein L, Switalla S, Prenzler F, Seehase S, Pfennig O, Förster C, Fieguth H, Braun A and Sewald K. 2014. Assessment of immunotoxicity induced by chemicals in human precision-cut lung slices (PCLS). Tox in Vitro 28:588–599.
OECD (2010) Test No. 429: Skin Sensitisation: Local Lymph Node Assay, OECD Guidelines for the Testing of Chemicals, Section 4, OECD Publishing. doi: 10.1787/9789264071100-en.
Pauluhn J. 2014. Development of a respiratory sensitization/elicitation protocol of toluene diisocyanate (TDI) in Brown Norway rats to derive an elicitation-based occupational exposure level. Toxicology 319: 10–22.
BERNSTEIN, J. A., GHOSH, D., SUBLETT, W. J., WELLS, H. & LEVIN, L. 2011. Is trimellitic anhydride skin testing a sufficient screening tool for selectively identifying TMA-exposed workers with TMA-specific serum IgE antibodies? J Occup Environ Med, 53, 1122-7.
DAVIES, J. M., PLATTS-MILLS, T. A. & AALBERSE, R. C. 2013. The enigma of IgE+ B-cell memory in human subjects. J Allergy Clin Immunol, 131, 972-6.
KIMBER, I., DEARMAN, R. J. & BASKETTER, D. A. 2014. Diisocyanates, occupational asthma and IgE antibody: implications for hazard characterization. J Appl Toxicol, 34, 1073-7.
MOVÉRARE, R., BLUME, K., LIND, P., CREVEL, R., MARKNELL DEWITT, Å. & COCHRANE, S. 2017. Human Allergen-Specific IgG Subclass Antibodies Measured Using ImmunoCAP Technology. Int Arch Allergy Immunol, 172, 1-10.
QUIRCE, S. 2014. IgE antibodies in occupational asthma: are they causative or an associated phenomenon? Curr Opin Allergy Clin Immunol, 14, 100-5.