It is found that the blood half-life of an IgG antibody, which is a polypeptide having a FcRn binding region, can be controlled by a method comprising modifying a variable region residue of the IgG antibody exposed on the surface to thereby control the surface charge of the IgG antibody. It is confirmed that the antibody whose blood half-life is controlled by the method retains its activity practically. The method is widely applicable to any polypeptide having a FcRn binding region such as an IgG antibody, which can be recycled through a salvage pathway, regardless of the type of a target antigen.
