It is found that a molecule of an antibody which exhibits a weaker antigen-binding activity at a pH value in an early endosome compared with that at a pH value in a plasma can bind to two or more antigen molecules, and it is also found that the antibody has a long half-life in a plasma and is improved in the period during which the antibody can bind to an antigen.本發明提供一種在早期內囊胞內pH的抗原結合活性較在血漿中pH的抗原結合活性弱的抗體,該抗體可以1分子與複數個分子的抗原結合,延長血漿中半衰期,改善可與抗原結合的時間。
