Immunopharmacological studies on TBX, a new antiallergic drug. (4). Effects on type II to IV allergic reactions and immunological functions in animal models.

The effects of 9-methyl-3-(1H-tetrazol-5-yl)-4H-pyrido[1,2-a]pyrimidin-4-one potassium salt (TBX) on type II to IV allergic reactions and immunological functions were investigated in animal models. Types II to IV allergic reactions in rodents were unaffected in vivo by TBX, even at higher doses than those capable of completely inhibiting the type I allergic reaction. However, both complement-mediated hemolysis via the classical pathway and hypotonic shock-induced hemolysis were slightly inhibited in vitro only by a high concentration of the drug (10(-4) g/ml). In the mouse system, TBX had no ability to suppress anti-hapten IgE antibody formation as well as hemagglutinin formation and to inhibit the proliferation of spleen cells induced by non-specific T and B cell mitogens. The results obtained indicate that TBX is an antiallergic drug essentially devoid of inhibitory actions on types II to IV allergic reactions and immunological functions, thus indicating that it is a specific inhibitor of type I allergic reactions.