(Problem) To provide: a Fc region variant which has such a property that the binding activity to Fc?RIIb is increased and/or the binding selectivity to Fc?RIIb compared with that to Fc?RIIa (type R) is increased when compared with a polypeptide that contains a Fc region having no amino acid modification introduced thereinto； a polypeptide containing the Fc region variant； a pharmaceutical composition containing the polypeptide； a therapeutic or prophylactic agent for immune inflammatory diseases, which comprises the pharmaceutical composition； methods for producing the aforementioned products； and a method for increasing the binding activity to Fc?RIIb and also increasing the binding selectivity to Fc?RIIb compared with that to Fc?RIIa (type R). (Solution) It is found that a polypeptide which contains an antibody Fc region variant comprising an amino acid sequence containing the combination of the amino acid modification at position-238 as numbered in accordance with the EU numbering method and the amino acid modification at another specific position has such a property that the binding activity to Fc?RIIb is increased and/or the binding selectivity to Fc?RIIb compared with that to Fc?RIIa (type R) is increased.
