ALLERGEN-INDUCED SYNTHESIS OF INTERLEUKIN-5, BUT NOT OF IGE, IS A KEYMECHANISM LINKED TO SYMPTOMATIC EPISODES OF SEASONAL ALLERGIC RHINITIS IN SENSITIZED INDIVIDUALS

Some individuals with detectable levels of Japanese cedar (Criptomeria japonica) pollen-specific immunoglobulin (Ig)E in serum have no appar ent nasal symptoms during the pollen season. The response of CD4(+) T- helper (Th) cells to the pollen allergen might differ fundamentally be tween asymptomatic and symptomatic individuals who are already sensiti zed to the pollen. The aim of this study was to discern the possible d ifferences in responses of peripheral blood mononuclear cells (PBMCs) to the pollen allergen between asymptomatic and symptomatic subjects w ho have been sensitized to the pollen. This study included 20 nonatopi c healthy volunteers (non-atopic group) and 48 patients who had detect able levels of the pollen-specific IgE before the pollen season in 199 7. In the review of nasal symptoms during the pollen season 1997, 24 p atients had typical symptoms of seasonal allergic rhinitis (symptomati c group), and the remainder had no seasonal aggravation of nasal sympt oms (asymptomatic group). Peripheral blood mononuclear cells (1.0x10(7 ) cells/well) were obtained from each individual during the pollen sea son and cultured in the absence or presence of 12.5 mu g of Cry j 1 fo r 4 days. The concentrations of IgE, interleukin-5 (IL-5), and interfe ron-gamma (IFN-gamma) in the culture supernatants were measured. The l evels of IgE produced by Cry j 1-stimulated PBMCs of the asymptomatic and symptomatic,groups were significantly higher than those of the non -atopic group, but did not differ between the asymptomatic and symptom atic groups. The levels of IL-5 produced by Cry j 1-stimulated PBMCs d id not differ significantly between the non-atopic group and the asymp tomatic group, but the levels of IL-5 were significantly higher in the symptomatic group than in the asymptomatic group as well as the nonat opic group. The levels of IFN-gamma produced by Cry j-1 stimulated PBM Cs did not differ significantly among the three groups. In conclusion, our study has suggested that Japanese cedar pollen-induced synthesis of IL-5, but not of IgE or IFN-gamma, is likely to be a key mechanism linked to the symptomatic episode of seasonal allergic rhinitis in ind ividuals sensitized to the pollen.