It is an object of the present invention to provide a high affinity
antibody effective as a diagnostic or therapeutic for various diseases; a
transgenic mammal for producing the high affinity antibody; and a
medicine comprising the high affinity antibody or a cell producing the
high affinity antibody. According to the present invention, a transgenic
mammal carrying a GANP gene transferred thereinto, its progeny, or a part
thereof, and a method of producing a high affinity antibody using the
same are provided.