Allergen-induced mRNA expression of IL-5, but not of IL-4 and IFN-gamma, in peripheral blood mononuclear cells is a key feature of clinical manifestation of seasonal allergic rhinitis

Objectives: To investigate the allergen-induced messenger RNA (mRNA) expres sion of interleukin (IL) 4, IL-5 and interferon gamma (IFN-gamma) in periph eral blood mononuclear cells from individuals sensitized by Japanese cedar (Cryptomeria japonica) pollens, and to elucidate the clinical role of IL-4, IL-5, and IFN-gamma in the allergen sensitization and clinical manifestati on of allergic disorders. Design: This study included 30 patients sensitized to the pollen and 14 non atopic healthy volunteers. Peripheral blood mononuclear cells (1.0 x 10(6) cells/mL) of each individual were cultured at 37 degrees C for 24 hours in the presence of 10 mu g/mL of Cry j 1, a major allergen of the pollens. Tot al cellular RNA was extracted from the peripheral blood mononuclear cells, and IL-4, IL-5, and IFN-gamma mRNA expression was determined with a reverse transcriptase polymerase chain reaction. Results: From the results of a survey of symptom diary cards and interviews regarding nasal symptoms during the pollen season in 1998, we found that 2 0 patients (symptomatic group), but not 10 patients (asymptomatic group), h ad typical symptoms of seasonal allergic rhinitis. Interleukin 4 mRNA was n ot expressed in the nonatopic subjects but was expressed in 9 asymptomatic patients and in 17 symptomatic patients. Interleukin 5 mRNA was exclusively expressed in the symptomatic patients. Interferon gamma mRNA expression di d not differ significantly among the nonatopic subjects, asymptomatic patie nts, and symptomatic patients. Conclusions: This study has clearly highlighted an interesting and new conc ept that IL-4 is implicated in allergen sensitization bur not in clinical m anifestation, and that IL-5 may not be a feature of atopy in itself but see ms to be a hallmark of clinical manifestation of ongoing atopic diseases.