T-cell and a prostate cancer cell. Coloured scanning electron micrograph (SEM) of a T-cell (red) and a prostate cancer cell. T-cells are a component of the body's immune system. CAR T-cell therapy takes T-cells from a cancer patient's blood and modifies them to recognize a specific protein found on patient's tumour cells. When reintroduced to the patient the T-cells find and destroy the tumour cells. The newest form of CAR T-cell therapy, now in clinical trials, uses "memory" T-cells which remain in the body after attacking the cancer. The hope is that memory T-cells may provide an active reservoir of cancer-killing cells capable of stopping further tumours. Magnification: x4000 at 10cm wide.