Similar immune mechanisms control experimental airway eosinophilia elicited by different allergens and treatment protocols

Evelyn J Hyde,Sayani Ghosh,Franca Ronchese,Kirsty A Wakelin,Naomi J Daniels

doi:10.1186/s12865-019-0295-y

Abstract

BackgroundMouse 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 cell hyperplasia and cellular infiltration in lung, it is not established whether they do so by involving the same mechanisms.ResultsWe 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 Class II (MHCII) deficiency and lack of conventional CD4+ T cells had the most profound effect, essentially ablating airway eosinophilia and goblet cell hyperplasia in all models. In contrast, Thymic stromal lymphopoietin receptor (TSLPR) deficiency greatly reduced eosinophilia but had a variable effect on goblet cells. CD1d deficiency 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.ConclusionAll 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.

Highlights

Mouse models have been extremely valuable in identifying the fundamental mechanisms of airway inflammation that underlie human allergic asthma
Animal models of allergic airway inflammation faithfully replicate several of these hallmarks of the late asthmatic response: type 2-associated cytokines such as IL-4, IL-5 and IL-13 can be found in the broncho-alveolar lavage (BAL) and are responsible for the observed inflammatory pathologies [3, 4]
We found that in all cases total cellularity and eosinophil percentages and numbers in BAL were greatly reduced in Thymic stromal lymphopoietin receptor (TSLPR)-KO mice compared to WT (Fig. 3a–d)

Summary

Introduction

Mouse models have been extremely valuable in identifying the fundamental mechanisms of airway inflammation that underlie human allergic asthma. All models elicit similar hallmarks of allergic airway inflammation, including airway eosinophilia, goblet cell hyperplasia and cellular infiltration in lung, it is not established whether they do so by involving the same mechanisms. Broncho-alveolar lavage of segmentally challenged allergic asthma patients has revealed the presence of eosinophils and Th2 cells in the airway with increased mucin, Th2 cytokines and increased smooth muscle mass [2]. Animal models of allergic airway inflammation faithfully replicate several of these hallmarks of the late asthmatic response: type 2-associated cytokines such as IL-4, IL-5 and IL-13 can be found in the broncho-alveolar lavage (BAL) and are responsible for the observed inflammatory pathologies [3, 4].

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