We had previously reported that antigen-induced IL2 responsiveness by lymphocytes can be used to identify etiological allergens and to monitor the clinical activity in atopic diseases. The effect of Kanpo-Medicines; Saiboku-to, Syoseiryu-to, Sairei-to, antiallergic agents, on Dermatophagoides farinae (Df) antigen-induced interleukin 2 (IL2) responsiveness from patients with bronchial asthma was studied and compared among 3 Kanpo-medicines. Allergen-sensitized patient mononuclear cells pretreated with 30-30,000 ng/ml doses of Saiboku-to for 16 hours failed to induce responsiveness to IL2 on stimulation with Df antigen in 8 patients out of 11 (73%). The cells treated with 30 micrograms/ml of Syoseiryu-to also failed to introduce the response in 6 out of 10 (60%) with less frequency compared with Saiboku-to. Sairei-to also suppressed the response on stimulation with a 10 micrograms/ml dose alone in 1 x 10(-3)-1 x 10(-4)ng/ml doses examined in 6 patients out of 17 (35%) with much less frequency and % inhibition. Also Saiboku-to and Sairei-to not Syoseiryu-to inhibited purified protein derivatives (PPD)-induced IL2 responsiveness. However. These agents failed to suppress the Con A-induced IL2 responsiveness. Antigen-presenting adherent cells were more susceptible to any Kanpo-medicines studied rather than IL2-responding T cells except Sairei-to. These results indicated that Kanpo-medicines studied have a weak immuno-suppressive property resulting in inhibiting antigen-induced IL2-responsiveness. Suppressive effects of each Kanpo-medicine seemed to depend on combinations and doses of their elements (Syouyaku). Decreased suppressive effect of higher doses of any Kanpo-medicine was likely to be mitogenic effects of each element on T cells.