A method of making a dual specific antibody, or antigen-binding fragment thereof, comprising a variable heavy chain domain and a variable light chain domain, wherein the VH and VL of the dual specific antibody pair together to form an antigen-binding site that specifically binds to a first epitope and a second epitope, said method comprising the steps of: (a) providing an antibody that comprises a VH and VL, wherein the VH and VL pair together to form an antigen-binding site that binds to a first epitope but not the second epitope and wherein said antibody comprises at least one amino acid at position 32, 50, or 91 according to the Kabat numbering system of the VL that is electrostatic or hydrophobic, and further wherein the antibody of comprises: (i) a light chain variable region complementarity determining region CDRL1 comprising the amino acid sequence KASQSVINDAA (SEQ ID NO: 9), a CDRL2 comprising the amino acid sequence YTSHRYT (SEQ ID NO: 10), and a CDRL3 comprising the amino acid sequence QQDYTSPWTF (SEQ ID NO: 11); and (ii) a heavy chain variable region complementarity determining region CDRH1 comprising the amino acid sequence DYSMH (SEQ ID NO: 13), a CDRH2 comprising the amino acid sequence VWINTETGEPTYADDFK (SEQ ID NO: 17), and a CDRH3 comprising the amino acid sequence GGIFYGMDY (SEQ ID NO: 20); (b) altering the nucleic acid sequence encoding the VH of the antibody of step (a) in the absence of mutation to the VL, wherein one or more solvent accessible amino acid residues at an amino acid residue position selected from the group of consisting of positions 33, 34, 50-58, and 95-97 according to the Kabat numbering system of the VH are altered; (c) expressing VL and the altered VH of step (b); and (d) selecting a dual specific antibody, or antigen-binding fragment thereof, comprising the VL and the altered VH of step (c), wherein the VH and VL pair together to form an antigen binding site that specifically binds to the first epitope and the second epitope. (a) providing an antibody that comprises a VH and VL, wherein the VH and VL pair together to form an antigen-binding site that binds to a first epitope but not the second epitope and wherein said antibody comprises at least one amino acid at position 32, 50, or 91 according to the Kabat numbering system of the VL that is electrostatic or hydrophobic, and further wherein the antibody of comprises: (i) a light chain variable region complementarity determining region CDRL1 comprising the amino acid sequence KASQSVINDAA (SEQ ID NO: 9), a CDRL2 comprising the amino acid sequence YTSHRYT (SEQ ID NO: 10), and a CDRL3 comprising the amino acid sequence QQDYTSPWTF (SEQ ID NO: 11); and (ii) a heavy chain variable region complementarity determining region CDRH1 comprising the amino acid sequence DYSMH (SEQ ID NO: 13), a CDRH2 comprising the amino acid sequence VWINTETGEPTYADDFK (SEQ ID NO: 17), and a CDRH3 comprising the amino acid sequence GGIFYGMDY (SEQ ID NO: 20); (b) altering the nucleic acid sequence encoding the VH of the antibody of step (a) in the absence of mutation to the VL, wherein one or more solvent accessible amino acid residues at an amino acid residue position selected from the group of consisting of positions 33, 34, 50-58, and 95-97 according to the Kabat numbering system of the VH are altered; (c) expressing VL and the altered VH of step (b); and (d) selecting a dual specific antibody, or antigen-binding fragment thereof, comprising the VL and the altered VH of step (c), wherein the VH and VL pair together to form an antigen binding site that specifically binds to the first epitope and the second epitope.