Similar immune mechanisms control experimental airway eosinophilia elicited by different allergens and treatment protocols
2019
Mouse models have been extremely valuable in identifying the fundamental mechanisms of airway inflammation that underlie human allergic asthma. Several models are commonly used, employing different methods and routes of sensitisation, and allergens of varying clinical relevance. Although all models elicit similar hallmarks of allergic airway inflammation, including airway
eosinophilia,
goblet cellhyperplasia and
cellular infiltrationin lung, it is not established whether they do so by involving the same mechanisms. We compared the impact of inactivation of various innate or adaptive immune genes, as well as sex, in different models of allergic airway inflammation in mice of C57BL/6 background. Chicken ovalbumin (OVA) and
house dust mite(HDM) were used as allergens in settings of single or multiple intranasal (i.n.) challenges, after sensitisation in adjuvant or in adjuvant-free conditions. Eosinophil numbers in the broncho-alveolar lavage and lung histopathology were assessed in each model. We found that Major Histocompatibility
Complex ClassII (MHCII) deficiency and lack of conventional CD4+ T cells had the most profound effect, essentially ablating airway
eosinophiliaand
goblet cellhyperplasia in all models. In contrast,
Thymic stromal lymphopoietinreceptor (TSLPR) deficiency greatly reduced
eosinophiliabut had a variable effect on
goblet cells.
CD1ddeficiency and lack of Natural Killer T (NKT) cells moderately impaired inflammation in OVA models but not HDM, whereas sex affected the response to HDM but not OVA. Lastly, defective Toll-like receptor (TLR)4 expression had only a relatively modest overall impact on inflammation. All the models studied were comparably dependent on adaptive CD4+ T cell responses and TSLP. In contrast, sex, NKT cells and TLR4 appeared to play subtler and more variable roles that were dependent on the type of allergen and mode of immunization and challenge. These results are consistent with clinical data suggesting a key role of CD4+ T cells and TSLP in patients with allergic asthma.
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