The present inventors succeeded in improving the antibody constant region to have increased stability under acid conditions, reduced heterogeneity originated from disulfide bonds in the hinge region, reduced heterogeneity originated from the H chain C terminus, and increased stability at high concentrations as well as in discovering novel constant region sequences having reduced Fcγ receptor-binding activity, while minimizing the generation of novel T-cell epitope peptides. As a result, the present inventors successfully discovered antibody constant regions with improved physical properties (stability and homogeneity), immunogenicity, safety, and retention in plasma.本發明成功地改良抗體固定區以增加酸性條件下之安定性、降低源自鉸鏈區雙硫鍵的異質性、降低源自H鏈C終端之異質性、以及增加於高濃度之安定性，並發現具有降低的Fcγ受體結合活性之新穎固定區序列，而產生最小化新穎T-細胞抗原決定基肽。其結果，本發明之抗體固定區具有良好的物理性質(安定性與同質性)、免疫性、安全性與血漿中停留時間。
