In vivo studies using therapeutic mAb gene transfer after CCR4+ tumor cell implantation demonstrated the potent antitumor activity of the mAb h1567. In addition, the in vivo effector cells that mediate tumor cell killing through h1567 Fc binding to Fcc receptors, namely FccRIIIa (CD16A), were delineated. These studies suggest that mAb 1567 can serve as an effective antibodydirected therapy for immunodepleting malignant CTCL cells and may minimize collateral damage to the already compromised immune system. Furthermore, in the context of anti-cancer mAb therapies that require frequent and repeated administration, this AAV-based therapeutic antibody gene transfer strategy might serve as an alternative platform for their delivery.