T lymphocytes and cancer cells. Coloured scanning electron micrograph (SEM) of T lymphocyte cells (smaller round cells) attached to cancer cells. 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 tumor 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: x600 at 10 centimetres wide