The present inventors have successfully prepared an antibody Fc region dimer that has binding activity against each of an antigen and FcγR, but does not bind to the antigen and the FcγR at the same time, and a polypeptide comprising the Fc region dimer. The present invention enables the preparation of a multispecific binding polypeptide capable of avoiding an adverse reaction that may be caused by its binding to an antigen and FcγR at the same time. Thus, the present invention provides a polypeptide suitable as a drug.
