Improper or inadequate glycosylation of a monoclonal antibody produced in mammalian cell culture often results in poor effector function and disappointing clinical efficacy. Bailey and colleagues have addressed this problem by introducing into Chinese hamster ovary (CHO) cells a tetracycline–regulated glycosyltransferase capable of incorporating appropriate oligosaccharides into an antineuroblastoma monoclonal antibody. When the antibody was expressed in these engineered CHO cells, antibody–dependent cellular cytotoxicity could be optimized according to the level of glycosyltransferase induction (p. 176 ).