Abstract
In this study, we investigated the pharmacological reactions induced by ibudilast to the complement system with the aim of clarifying the functional relation of the complement system to allergic reactions and pathology in patients with bronchial asthma. Complement hemolytic activities (CH50 and ACH50), complement profile, anaphylatoxins (C3a and C5a) and complement fragments (Bb, iC3b and C4d) were measured in 20 patients with bronchial asthma. One of antiasthmatic activities induced by ibudilast was concluded to be brought about though inactivation of the alternative complement pathway working on type III allergic reaction. Ibudilast increased the complement fragment Bb in the patients' plasma with the fairly controled bronchial asthma. This increase in circulating Bb was suspected to be a result of inactivation of intermediate complement complexes, for example C3b・ Bb・P, because the amounts in plasma of C3 and C5 showed no changes, while those of factor, B, P, H and I were decreased by ibudilast administration in patients with fairly controled bronchial asthma. This antiasthmatic ability of ibudilast was restrained in those patients whose peripheral leukocytopenia was advanced before ibudilast administration, and in those whom ibudilast did not provoke an increase in the plasma level of iC3b, or did not prevent the serum level of C5 from increasing. In those unfairly controled cases, enough anaphylatoxins, especially C5a might be produced to make the margination of peripheral neutrophils to the lung and increase CR3 on neutrophils binding with iC3b.
