The Natural Killer white blood cell in red is drawn to the cancerous B cell which has been treated with rituximab. It latches on to the side of the cell where the protein CD20 (which is shown in green) has collected. The cell is then destroyed. The Natural Killer then moves on to destroy another B cell. By latching on to the side where the CD20 is gathered the NK cell has an 80% success rate in destroying the cancerous B cell.