CAR T cell cancer immunotherapy, illustration. Chimeric antigen receptor (light blue, upper left) binding to CD19 molecules (pink, centre left and centre) on a leukaemia (blood cancer) cell. The CAR receptors are genetically engineered and embedded in a T-lymphocyte cell membrane to bind specifically to the CD19-antigen molecules. This activates a signal cascade in the T-cell leading to the segregation of vesicles that contain perforin and granzyme molecules. The perforins build channels for the granzymes which enter the leukaemia cell and activate the apoptosis (cell death) of the cancer cell.