(a) Toxin chain Monoclonal antibody Ricin Sbigella Diphtheria toxin toxin Immunotoxin (b) Immunotoxin Diphtheria toxin Tumor-specific antigen Endocytosis Endosome Release of toxin into cytosol Active EF-2- →Inactive EF.2 Active EF-2 →Inactive EF2 mRNA+aa十→Protein mRNA+aa→Protein