A method for producing an antibody, which comprises the steps of: (a) selecting an antigen having the property of binding two or more different target molecules; (b) identifying one or more antibody antigen binding domains that inhibit the activity of the antigen to bind one or more of said two or more target molecules by binding to the antigen while allowing the antigen to maintain the binding activity to at least one of said two or more target molecules; and optionally altering at least one amino acid in the domain; (c) selecting, from the one or more antibody antigen binding domains of (b), a domain whose antigen-binding activity changes according to the pH as described in (i) below, or calcium ion concentration as described in (ii) below; (i) the antigen-binding activity is lower in the range pH 5.8 to pH 6.0 than at pH 7.4, wherein the ratio of the KD value for antigen binding in the range pH 5.8 - pH 6.0 to the KD value for antigen binding at pH 7.4 (KD (pH 5.8 to pH 6.0) / KD (pH 7.4)) is 2 or more; or (ii) the antigen-binding activity is lower at a calcium ion concentration in the range 1 μM to 5 μM than in the range 0.5 mM to 2.5 mM, wherein the ratio of the KD value for antigen binding at a calcium concentration in the range 1 μM to 5 μM to the KD value for antigen binding at a calcium concentration in the range 0.5 mM to 2.5 mM (KD (1 μM to 5 μM Ca++) / KD (0.5 mM to 2.5 mM Ca++)) is 2 or more; (d) identifying at least one IgG Fc region, optionally altering at least one amino acid in the region, and selecting an IgG Fc region that has human FcRn-binding activity in the range pH 5.8 to pH 6.0 and wherein the binding activity of said IgG Fc region to human FcRn or a human Fcγ receptor that is human FcγRIa, FcγRIIa, FcγRIIb, or FcγRIIIa at pH 7.4 is higher than the binding activity of native human IgG to said human FcRn or said human Fcγ receptor; and (e) preparing an antigen-binding molecule comprising the one or more antibody antigen binding domains selected in step (c) and the IgG Fc region selected in step (d). (a) selecting an antigen having the property of binding two or more different target molecules; (b) identifying one or more antibody antigen binding domains that inhibit the activity of the antigen to bind one or more of said two or more target molecules by binding to the antigen while allowing the antigen to maintain the binding activity to at least one of said two or more target molecules; and optionally altering at least one amino acid in the domain; (c) selecting, from the one or more antibody antigen binding domains of (b), a domain whose antigen-binding activity changes according to the pH as described in (i) below, or calcium ion concentration as described in (ii) below; (i) the antigen-binding activity is lower in the range pH 5.8 to pH 6.0 than at pH 7.4, wherein the ratio of the KD value for antigen binding in the range pH 5.8 - pH 6.0 to the KD value for antigen binding at pH 7.4 (KD (pH 5.8 to pH 6.0) / KD (pH 7.4)) is 2 or more; or (ii) the antigen-binding activity is lower at a calcium ion concentration in the range 1 μM to 5 μM than in the range 0.5 mM to 2.5 mM, wherein the ratio of the KD value for antigen binding at a calcium concentration in the range 1 μM to 5 μM to the KD value for antigen binding at a calcium concentration in the range 0.5 mM to 2.5 mM (KD (1 μM to 5 μM Ca++) / KD (0.5 mM to 2.5 mM Ca++)) is 2 or more; (i) the antigen-binding activity is lower in the range pH 5.8 to pH 6.0 than at pH 7.4, wherein the ratio of the KD value for antigen binding in the range pH 5.8 - pH 6.0 to the KD value for antigen binding at pH 7.4 (KD (pH 5.8 to pH 6.0) / KD (pH 7.4)) is 2 or more; or (ii) the antigen-binding activity is lower at a calcium ion concentration in the range 1 μM to 5 μM than in the range 0.5 mM to 2.5 mM, wherein the ratio of the KD value for antigen binding at a calcium concentration in the range 1 μM to 5 μM to the KD value for antigen binding at a calcium concentration in the range 0.5 mM to 2.5 mM (KD (1 μM to 5 μM Ca++) / KD (0.5 mM to 2.5 mM Ca++)) is 2 or more; (d) identifying at least one IgG Fc region, optionally altering at least one amino acid in the region, and selecting an IgG Fc region that has human FcRn-binding activity in the range pH 5.8 to pH 6.0 and wherein the binding activity of said IgG Fc region to human FcRn or a human Fcγ receptor that is human FcγRIa, FcγRIIa, FcγRIIb, or FcγRIIIa at pH 7.4 is higher than the binding activity of native human IgG to said human FcRn or said human Fcγ receptor; and (e) preparing an antigen-binding molecule comprising the one or more antibody antigen binding domains selected in step (c) and the IgG Fc region selected in step (d).