Allergen induced mRNA expression of interleukin-5, but not of interleukin-4 and interferon-gamma, in peripheral blood mononuclear cells obtained before the pollen season predicts the clinical efficacy of immunotherapy for seasonal allergic rhinitis.

Abstract

The primary aim of this study was to investigate whether the allergen-induced synthesis of cytokines by peripheral blood mononuclear cells (PBMCs) obtained immediately before the pollen season could predict the clinical efficacy of immunotherapy during the following pollen season. PBMCs (1.0 x 106 cells/ml) were obtained from 17 nonatopic subjects and from 60 patients receiving immunotherapy for seasonal allergic rhinitis (caused by Japanese cedar pollens) immediately before the pollen season of 1998, and were cultured for 24 h in the presence of 10 mg/ml of Cry j 1, a major allergen of Japanese cedar pollens, at 37 degrees C in a fully humidified 5% CO2 atmosphere. Total cellular RNA was extracted from the PBMCs, and the allergen-induced interleukin (IL)-4, IL-5 and interferon-gamma (IFN-gamma) mRNA expression was determined using a reverse transcription-polymerase chain reaction. According to the nasal symptoms during the pollen season of 1998, the 60 patients on immunotherapy were divided into 36 good responders (who had no nasal symptoms and no requirement for rescue medications) and 24 poor responders who needed rescue medications to control nasal symptoms. Neither IL-4 mRNA nor IL-5 mRNA was expressed in any of the 17 nonatopic individuals. By contrast, IL-4 mRNA was expressed in 26 good responders and in 22 poor responders, and IL-5 mRNA was expressed in eight good responders (22.2%) and in 23 poor responders (95.8%). IFN-gamma mRNA was expressed in four nonatopic subjects, in nine good responders and in seven poor responders. The expression of IFN-gamma did not differ significantly among the nonatopic subjects, the good responders and the poor responders. The mRNA expression of IL-5 (P < 0.0001), but not of IL-4 (P = 0.0999) and IFN-gamma (P = 0. 7713), differed significantly between the good and poor responders. Therefore, our study has highlighted that positive expression of IL-5 mRNA in PBMCs sampled immediately before the pollen season could be predictive of a poor clinical outcome of immunotherapy during the following pollen season and that the down-regulation of IL-5 mRNA expression in PBMCs could be an important mechanism of pollen immunotherapy related to the clinical efficacy.