Illustration of a chimeric antigen receptor (CAR) T cell (blue) attacking chronic myeloid leukaemia (CML, dark purple). This cancer affects the myeloid tissue (bone marrow), specifically the white blood cell precursors (myeloblasts) that form a type of white blood cell known as granulocytes. These immature cells fill up the bone marrow and spill into the bloodstream and circulate throughout the body. The cells do not work properly to fight infections and their increased production reduces the production of red blood cells leading to anaemia and fatigue. Chronic leukaemias progress slowly and may not be diagnosed for a number of years. CAR-T therapy is a type of immunotherapy that genetically modifies a patients own T cells, a form of white blood cell, to recognise and destroy cancer cells.