Monoclonal antibodies directed against tumor antigens have proven effective for treating some forms of cancer. Despite the increasing use of monoclonal antibody therapy, it is not clear how these antibodies drive tumor removal.

In this issue of the Journal of Clinical Investigation, Marjolein van Egmond and colleagues at the VU University Medical Center found that macrophage populations mediate tumor cell removal following monoclonal antibody treatment by actively phagocytosing tumor cells. Macrophage-dependent tumor cell removal required both the high affinity and low affinity Fc receptors.

This study suggests that monoclonal antibody therapies that are optimized to enhance macrophage recruitment and activity may enhance removal of circulating tumor cells in cancer patients.