ERBB2 and cancer: The trifunctional immunoglobulin ertumaxomab (Fresenius Biotech, Hamburg, Germany) is a bispecific antibody.151 It targets HER2 on cancer cells and triggers T-cell-specific CD3 antigens and accessory cells, like macrophages, dendritic cells, and natural killer cells, at the sites of tumor metastases.152,153 Whether its molecular structure affects the immunological mechanism or induces cellular immunity against ertumaxomab is still unknown.