Regulation of T-cell activation in the airway mucosa of rats expressing low versus high IgE responder phenotype

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We have established an experimental rat model of allergic airways inflammation which mimics human asthma. Interactions occurring between airway mucosal dendritic cells and CD4+ Th2 (effector) cell populations are responsible for the late phase response (LPR) component of asthma exacerbations, including airways hyperresponsiveness (AHR). We have previously demonstrated that termination of the LPR and prevention of its continual recurrence in the face of ongoing aeroallergen challenge is established via the induction of a state of dynamic equilibrium, mediated by local T regulatory cells (Treg) which act to functionally silence local Th2 memory (effector) cells. Maintenance of protective Treg activity is dependent upon continuing allergen exposure as cessation of exposure leads to waning of Treg numbers and function and release of mucosal allergen specific Th2 cells from control. These studies have primarily involved low IgE responder (LR) PVG rats (normals or nonatopics). The present study will focus on elucidating the control of Th2 dependent immune responses to inhaled antigen in high IgE responder (HR) BN rats (atopics). Studying these two strains in parallel enables a comparison between the extremes of the spectrum of susceptibility to both the induction and the expression of Th2 immunity in the airways. A more detailed understanding of the cellular interactions occurring within the airway mucosa and draining lymph nodes and the mechanisms responsible for the maintenance of immunological homeostasis within the airways will provide new insights into the pathogenesis of inflammatory airway diseases such as atopic asthma. This will enable further development and possibly illuminate other avenues of intervention for more effective therapeutic strategies used in the control of asthma, which is the long term goal of this research.