 The Fab, or fragment antigen binding region of the antibody, binds to the antigen on the EGFr expressing tumor cells.Through an immunological response, the body’s natural killer (NK) cells, which are a type of lymphocyte, recognize and bind to the Fc portion on the antibody through an Fc receptor, CD16.The NK cell is then activated through the cross linking of the Fc receptors which sends a signal to induce apoptosis and cell death.