CAR T cell cancer immunotherapy. Illustration of a chimeric antigen receptor (CAR) T cell (top right) recognising cancerous cells (centre). CAR T cells are white blood cells from the body's immune system that have been modified to fight cancer. A blood sample is taken from a cancer patient, and the T-cells extracted from it. The T-cells are then genetically engineered to produce chimeric antigen receptors (CARs, protrusions) on their surfaces that recognise targets (brown) on the patient's cancerous cells. The patient receives an infusion of the CAR T-cells, which attack any cancerous cells and destroy them.