Illustration showing chimeric antigen receptor (CAR) T cells (blue) being used to treat chronic myeloid leukaemia (CML) cells (dark purple). CML is a cancer that affects the myeloid tissue (bone marrow), specifically the white blood cell precursors (myeloblasts) that form a type of white blood cell known as granulocytes. CAR-T cells are a patients own T cells, a form of white blood cell, that have been genetically modified to recognise and destroy certain cancer or autoimmune cells that might otherwise be tolerated by the immune system. Healthy red blood cells (red discs) and white blood cells (translucent/light purple) are visible in the background.