Airway hyperresponsiveness in mouse models of asthma is associated with activated T cells in the airways

Adoptive transfer of activated T cells has been shown to induce allergic responses in the lung, however, direct physiological evidence of whether these T cells home to the airways is lacking. This study aimed to determine the role of CD4+ T cells in the generation of airway hyperresponsiveness (AHR) in mouse models of asthma. Methods: (1) 129/Sv, C57BL/6 and BALB/c mice were sensitized and challenged with ovalbumin (OVA). AHR, inflammatory cells, serum IgE and IgG1 and the number of CD4+ CD69+ T cells in the trachea and peripheral lung were measured. (2) DO11.10 transgenic T cells that recognize OVAwere transferred to naive BALB/c recipients. Recipient mice were primed and challenged with OVAand assessed forAHR and serum antibodies. (3) Naive BALB/c mice were passively sensitized with high titre IgE/IgG1 titre serum, challenged with OVA and assessed for AHR. Results: (1) AHR to inhaled methacholine (MCh) was induced by OVA in BALB/c mice only. This correlated with the presence of CD4+ CD69+ T cells and IgG1 . (2) After 5 OVA challenges naive BALB/c mice primed with DO11.10 T cells demonstrated AHR (p=0.049) to MCh. (3) Passive transfer of high titre IgE/IgG1 serum did not result in AHR. Conclusions: The presence of AHR in BALB/c mice was linked to the numbers of CD4+ CD69+ T cells and IgG1. Adoptive transfer of T cells that recognize OVA resulted in AHR following challenge suggesting that these T cells traffic to the airway after challenge. This could not be replicated by passively sensitizing mice with high IgE/IgG1 titre serum alone. This study highlighted the potential role of CD4+ T cells in the development of AHR and further studies using this system may be able to dissect the mechanism by which this occurs.