PROBLEM TO BE SOLVED: To provide an antibody constant region that has improved physical properties (stability and heterogeneity), immunogenicity (antigenicity), safety, and/or half-life in plasma； and an antibody comprising the constant region.SOLUTION: In an antibody having a specific amino acid sequence, a human antibody constant region comprises an amino acid sequence in which an amino acid at a specific position in an IgG2 constant region and/or IgG4 constant region is substituted, and an anti-IL-6 receptor antibody comprises the constant region.SELECTED DRAWING: None【課題】物性（安定性，ヘテロジェニティー），免疫原性（抗原性），安全性、および／または、血漿中半減期が改善された抗体定常領域および該定常領域を含む抗体の提供。【解決手段】特定のアミノ酸配列を有する抗体において、ＩｇＧ２定常領域および／またはＩｇＧ４定常領域における特定位のアミノ酸が置換されたアミノ酸配列を有するヒト抗体定常領域、及び、該定常領域を有する抗ＩＬ－６レセプター抗体。【選択図】なし
