Allergen-induced synthesis of interleukin-5, but not of IgE, is a key mechanism 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 apparent nasal symptoms during the pollen season. The response of CD4+ T-helper (Th) cells to the pollen allergen might differ fundamentally between asymptomatic and symptomatic individuals who are already sensitized to the pollen. The aim of this study was to discern the possible differences in responses of peripheral blood mononuclear cells (PBMCs) to the pollen allergen between asymptomatic and symptomatic subjects who have been sensitized to the pollen. This study included 20 non-atopic healthy volunteers (non-atopic group) and 48 patients who had detectable levels of the pollen-specific IgE before the pollen season in 1997. In the review of nasal symptoms during the pollen season 1997, 24 patients had typical symptoms of seasonal allergic rhinitis (symptomatic group), and the remainder had no seasonal aggravation of nasal symptoms (asymptomatic group). Peripheral blood mononuclear cells (1.0 x 10(7) cells/well) were obtained from each individual during the pollen season and cultured in the absence or presence of 12.5 microg of Cry j 1 for 4 days. The concentrations of IgE, interleukin-5 (IL-5), and interferon-gamma (IFN-gamma) in the culture supernatants were measured. The levels 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 symptomatic groups. The levels of IL-5 produced by Cry j 1-stimulated PBMCs did not differ significantly between the non-atopic group and the asymptomatic group, but the levels of IL-5 were significantly higher in the symptomatic group than in the asymptomatic group as well as the non-atopic group. The levels of IFN-gamma produced by Cry j 1-stimulated PBMCs 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 individuals sensitized to the pollen.