Schematic representation of DCH and variants. (A) cDNA domains encoding scFv HD70-IL-2 and scFv HD70-GM-CSF polypeptide chains. Structure of (B) the DCH fusion protein; (C) DCH-mu variant with amino acid mutations in the hypervariable regions of the V_L and V_H domains; and (D) SCH variant without an IL-2 fusion at the C kappa C-terminus. Abbreviations: HD70 V_L and V_H, light and heavy chain variable region domains derived from the human anti-Ep-CAM Ab HD70; GS linker, glycine-serine linker peptide (G₄S); IgG3 hinge, upper hinge region of human IgG3; C kappa, constant region domain of human Ig kappa light chain; CH1, first constant region domain of human IgG1 heavy chain; His6, hexahistidine tag.