Synthesis of 99mTc-anti-CD56 Monoclonal Antibody for Molecular Imaging of NK Cells: in Vitro and in Vivo Studies

Introduction: Natural killer (NK) cells, which account for up to 15% of peripheral blood lymphocytes, are important effectors of the innate immune system particularly involved in cancer cell removal. Imaging NK cell trafficking in vivo may be relevant to follow-up the efficacy of new therapeutic approaches aiming at increasing NK cell infiltration in tumors. Several attempts to image NK cells have been done in the past years by several groups using a direct labeling approach that involves cell purification from peripheral blood, radiolabelling and re-administration in patients. This approach has several limitations such as cell manipulation in culture and toxicity to radiation. We investigated a novel approach by indirect cell labeling using a humanized anti-CD56 monoclonal antibody (mAb) that binds NK cells in vivo. Specific aims of present study were (1) to efficiently radiolabel this mAb with 99mTechnetium and (2) to validate the binding activity of this radiolabelled antibody in a