It is found that a polypeptide, which contains an antibody Fc region variant that comprises an amino acid sequence composed of a combination of an alteration of an amino acid residue located at position-238 as numbered in accordance with the EU index and an alteration of another specific amino acid residue, has a reduced binding activity to all of active Fc?R's, especially to Fc?RIIa (type R), compared with polypeptides each containing a naturally occurring IgG Fc region, while maintaining the binding activity thereof to Fc?RIIb.
