To provide Fc variants with altered binding to FcRn.SOLUTION: The present application relates to a variant Fc region comprising at least one modification relative to a wild-type human Fc region, where the modification is selected from the group consisting of 434S, 252Y/428L, 252Y/434S, and 428L/434S, and the numbering is according to the EU index.SELECTED DRAWING: None【課題】FcRnへの変異結合を有するFc変異体の提供。【解決手段】本出願は、野生型ヒトFc領域と比べて少なくとも1つの修飾を含む変異Fc領域に関し、該修飾は、434S、252Y/428L、252Y/434S、および428L/434Sから成る群から選択され、付番はEUインデックスによる。【選択図】なし