Pollen immunotherapy inhibits T helper 1 and 2 cell responses, but suppression of T helper 2 cell response is a more important mechanism related to the clinical efficacy.

OBJECTIVES To investigate the allergen-induced IgE synthesis and cytokine production by peripheral blood mononuclear cells from patients with seasonal allergic rhinitis due to Japanese cedar (Cryptomeria japonica) pollens and to elucidate the immunological mechanisms related to the clinical efficacy of immunotherapy (IT) for seasonal allergic rhinitis. DESIGN This study included 51 patients with seasonal allergic rhinitis due to the pollen and 8 nonatopic healthy volunteers (nonatopic group). Thirty-nine patients had been undergoing IT using the pollen extracts for various lengths of time (IT group). The remaining 12 patients had never been treated with IT (untreated group). Peripheral blood mononuclear cells (3.3 x 10(6) cells per milliliter) from each individual were cultured with Cry j 1, 4.17 microg/mL. After 96 hours, culture supernatants were harvested to determine the concentrations of IgE, interleukin (IL) 5, interferon gamma (IFN-gamma), and tumor necrosis factor alpha (TNF-alpha). RESULTS The levels of IgE (P = .02), IL-5 (P<.01), and TNF-alpha (P = .05) were significantly higher in the untreated group than in the nonatopic group. The levels of IFN-gamma did not differ significantly between the untreated and the nonatopic groups (P = .19). The levels of IgE, IL-5, and IFN-gamma, but not of TNF-alpha, were inversely correlated with the duration (in years) of IT, and none of the levels of IgE (P = .74), IL-5 (P = .15), IFN-gamma (P = .61), and TNF-alpha (P = .55) differed significantly between the nonatopic group and those who had been treated with IT for 10 years or more. The levels of IL-5 were significantly lower in the good responders than in the poor responders to IT (P<.001), whereas the levels of total IgE (P = .20), IFN-gamma (P = .16), and TNF-alpha (P = .14) did not differ significantly between them. CONCLUSION The mechanisms responsible for the clinical efficacy of pollen IT are principally related to the tolerance or anergy of T helper 2 cells.