Illustration of CAR (chimeric antigen receptor) T cell immunotherapy, a process that is being developed to treat cancer. T cells (shown in cross-section), part of the bodyIllustrations immune system, are taken from the patient and have their DNA (deoxyribonucleic acid) modified by viruses (round) so that they produce chimeric antigen receptor (CAR) proteins (red). These proteins will be specific to the patientIllustrations cancer. They have an extracellular receptor component and an internal signalling and co-stimulatory domain. The modified T cells are then multiplied in the laboratory before being reintroduced to the patient.