The late asthmatic response is associated with baseline allergen‐specific proliferative responsiveness of peripheral T lymphocytes in vitro and serum interleukin‐5

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Abstract
Increasing insights into the mechanism underlying the allergen-induced late asthmatic response (LAR) have been gained with implication of activated eosinophils and CD4+ T lymphocytes. However, the patient characteristics that indicate the individual capacity to develop a LAR are not well-defined. In 22 subjects with mild to moderate house dust mite-allergic asthma, we investigated the relationship between the LAR and two other models of late-phase allergic inflammation, i.e. the allergen-specific proliferative response of peripheral blood T lymphocytes in vitro and the late cutaneous response. Non-specific bronchial responsiveness (PC20 histamine), lung function (FEV1), peripheral blood eosinophil count, early phase allergic skin sensitivity, and levels of total and specific immunoglobulin E (IgE) were determined prior to bronchial allergen challenge. Serum levels of interleukin-5 (IL-5) were measured before and at several time points after allergen inhalation. A significant correlation was found between the magnitude of the LAR and the allergen-specific proliferative response of peripheral T lymphocytes (r = 0.44, P = 0.04) but not the late cutaneous response. Stepwise-multiple linear regression of the magnitude of the LAR on the parameters analysed at baseline, resulted in a model combining PC20 histamine, early phase allergic skin sensitivity, and the allergen-specific proliferative response of peripheral T lymphocytes (R2 = 0.84, P < 0.001). No contribution of the late cutaneous response to the prediction of the LAR was found. Serum levels of IL-5 increased significantly at 6 h (P = 0.01) and 24 h (P = 0.003) after bronchial allergen challenge and correlated with the allergen-specific proliferative response of peripheral T lymphocytes in vitro (ρ = 0.48, P = 0.02). The findings in this study point to a role of TH2-lymphocyte responses in the development of the allergen-induced LAR. In allergic asthmatic patients, allergen-specific responsiveness of peripheral T-lymphocytes in vitro may serve as a model to determine the individual capacity to develop a LAR after allergen inhalation.