[Effects of YM-13650 on type I to type IV allergic reactions and immune responses in animals]

The effects of YM-13650 on experimental animal models of cell-mediated immune responses (type IV), antibody formation and type I to type III allergic reactions were investigated. YM-13650 in the dose range of 6.3 to 100 mg/kg, p.o., inhibited the picrylchloride-induced delayed type hypersensitivity (Pc-DTH) in mice when administered during the induction and the effector phases. The compound also inhibited the Pc-DTH enhanced by the pretreatment with cyclophosphamide, and even bilateral adrenalectomy failed to reduce the inhibitory effect of the compound on Pc-DTH in mice. YM-13650 in doses of 25 and 50 mg/kg, p.o., prolonged the survival time of allogenic skin grafts in mice. However, no significant effect was observed on hapten-specific IgE and HA antibody production and PFC formation in mice in doses up to 300 mg/kg, p.o. YM-13650 inhibited the passive Arthus reaction in guinea pigs and the reversed passive Arthus reaction in rats (type III). On the other hand, YM-13650 did not show any inhibitory effect on passive cutaneous anaphylaxis in rats (type I), Forssman shock in guinea pigs (type II) and carrageenin-induced paw edema in rats. These results indicate that YM-13650 suppresses not only cell-mediated immune responses but also type III allergic reactions without any influence on type I and type II allergic reactions as well as an acute inflammatory reaction.