Hela cancer cell and T cells. Coloured scanning electron micrograph (SEM) CD4+ T-cells (small cells) are examining a Hela cancer cell. T-cells are immune cells that patrol our body, killing infected or cancerous cells. T-cells detect their targets with a receptor that protrudes from their surface and binds to a target protein, or a displayed fragment of a protein, on the outside of other cells. What this means is that if you add the right receptor to T-cells, you can make them target anything you want, including a cancer. In CAR-t cell therapy a persons own T-cells can be extracted and genetically modified to express a "chimeric antigen receptor". This artificial receptor is made up of three proteins, one that recognises the cancer cell target and two that boost the T-cells activity. Specimen courtesy of Greg Towers and Lydia Newton, UCL. Magnification: x10000 when printed 10cm wide.