['Japanese cedar pollen is by far the most important cause of allergic rhinitis in Japan. In this study, we assessed the induction of blocking antibody during specific immunotherapy (SIT) using a recently standardized allergen extract from Japanese cedar pollen.', 'Basophils from nonallergic subjects were passively sensitized with serum samples prepared from pollinosis patients before and after SIT; all patients showed good clinical efficacy. The cells were then stimulated with the standardized allergen, and histamine release was measured. In most experiments, the basophil stimulation buffer contained 1% serum.', "Pollinosis patients' sera obtained both before and after SIT showed essentially similar sensitizing capacity for basophils. Basophil degranulation in response to a relatively low concentration of pollen extract was effectively suppressed by addition of post-SIT serum samples, indicating the presence of blocking antibody. The blocking antibody was IgG, and its potency varied widely among the donor patients."] Is blocking antibody generated in allergic rhinitis patients during specific immunotherapy using standardized Japanese cedar pollen extract?