This study comprised 130 adult patients with Japanese cedar pollen-specific
IgE in the serum and 15 non-atopic individuals. Eighteen patients had no seasonal aggravation of nasal symptoms during the pollen season in 1998 (asymptomatic group). Forty-two patients had not been treated previously with
immunotherapy and were treated with
antihistamine tablets during the pollen season in 1998 (medication group). Sixty-one patients had undergone variable periods of
immunotherapy using pollen extracts, and they were further divided into a good-IT group who responded markedly to
immunotherapy and a poor-IT group who responded poorly to
immunotherapy. The remaining nine patients had been treated with
immunotherapy for more than 12 years and all of them had stopped
immunotherapy by the end of May 1997 because they had no nasal symptoms for the last three pollen seasons and were considered to be cured of
seasonal allergic rhinitis (cure group). Peripheral blood mononuclear cells (PBMCs) were collected from each subject during the cedar pollen season in 1998 and were stimulated for 96 h with 10 micrograms/ml Cry j 1. The concentrations of
interleukin-5 (IL-5) and
interferon-gamma (IFN-gamma) in the culture supernatant were determined using an
enzyme-linked
immunosorbent assay. The levels of IFN-gamma did not differ significantly among the non-atopic group, the asymptomatic group, the medication group, the poor-IT group and the good-IT group. The level of
IL-5 in the asymptomatic group was not different from that in the non-atopic group. The levels of
IL-5 in the medication group, the good-IT group and the poor-IT group were significantly higher than in the non-atopic group. The level of
IL-5 in the good-IT group, but not in the poor-IT group, was significantly lower than in the medication group. The level of
IL-5 in the cure group was not significantly different from in the non-atopic group, and the level of IFN-gamma in the cure group was significantly lower than in the non-atopic group. In conclusion,
immunotherapy can decrease the pollen
allergen-induced synthesis of
IL-5, but not of IFN-gamma, and this immunological modulation is involved in the working mechanism of
immunotherapy related to its clinical efficacy. A tolerance or anergy of both TH1 and TH2 cells under
allergen stimulation may be an immunological indication of cure after the treatment of
seasonal allergic rhinitis. Thus, the suppression of synthesis of
IL-5 and IFN-gamma by
allergen-stimulated PBMCs is likely to be a reliable criterion for a possible cure of
seasonal allergic rhinitis after
immunotherapy.