Illustration showing an engineered receptor (light blue) on the surface of a T-lymphocyte binding specifically to CD19-antigen molecules (red) on a leukaemia cell. This activates a signal cascade in the T-cell leading to the segregation of vesicles that contain perforin and granzyme. The perforins build channels for the granzymes which enter the leukemia cell and activate finally the apoptosis (cell death) of the cancer cell.