Abstract: The present invention provides an experimental model animal which does not develop anaphylaxis, a type I allergy, can specifically induce Arthus reaction, a type III allergy, is not affected by type I allergy and evaluates type III allergy inflammation individually, and a method of screening a reaction accelerating or inhibitory substance in a type III allergy reaction through Fc?RIII by using said experimental model animal. In order to eliminate Fc?RIIB that demonstrates suppressive action to response through Fr?RIII, a mouse wherein the deletion mutation of both molecules of Lyn and Fc?RIIB are homozygotic (Lyn?IIB?) was generated by mating Lyn knockout mouse (Lyn?/?) and Fc?RIIB knockout mouse (Fc?RIIB?/?), and was used to measure and evaluate the deficiency of Fc?RIII function in systemic passive anaphylaxis and the reduction of Fc?RIII function in a bone marrow-derived mast cell, or the like.

Abstract: The present invention provides an experimental model animal which does not develop anaphylaxis, a type I allergy, can specifically induce Arthus reaction, a type III allergy, is not affected by type I allergy and evaluates type III allergy inflammation individually, and a method of screening a reaction accelerating or inhibitory substance in a type III allergy reaction through Fc&ggr;RIII by using said experimental model animal. In order to eliminate Fc&ggr;RIIB that demonstrates suppressive action to response through Fr&ggr;RIII, a mouse wherein the deletion mutation of both molecules of Lyn and Fc&ggr;RIIB are homozygotic (Lyn−IIB−) was generated by mating Lyn knockout mouse (Lyn−/−) and Fc&ggr;RIIB knockout mouse (Fc&ggr;RIIB−/−), and was used to measure and evaluate the deficiency of Fc&ggr;RIII function in systemic passive anaphylaxis and the reduction of Fc&ggr;RIII function in a bone marrow-derived mast cell, or the like.