Purification and properties of immunotoxins containing one vs. two deglycosylated ricin A chains

A method for the preparation of immunotoxins (ITs) containing one and two molecules of deglycosylated ricin A chain (dgA) bound to each molecule of anti-human CD22 mouse IgG1 monoclonal antibody is described. The cross-linking of antibody and dgA molecules was accomplished with N-succinimidyl-oxycarbonyl-alpha-methyl-(2-pyridyldithio) toluene. The two ITs were purified by successive chromatographies on Blue-Sepharose, Sephacryl S-200, Blue-Sepharose with NaCl gradient and Sephacryl S-300. The IT with two dgAs was seven-fold more cytotoxic to CD22+ Daudi cells than that containing one molecule of dgA.