T cells guard their territory, the body. They are peaceful, until they find signs of an intruder. These intruders are usually viruses or other pathogens, which are rigorously eliminated. In case of tumors, fighting off the invader is more difficult because cancerous cells are very similar to healthy tissue. The defense against tumors is therefore often linked to heavy collateral damage. For this purpose a special task force is necessary: CARTELTM cells. Activated by changes to their territory - the tumor microenvironment - they can be sure not to harm any healthy cells - and work hard to eliminate all intruders - the tumor cells. They are trained to infiltrate the tumor and only attack aberrant tissue, which is recognized by special traits: First via the tumor microenvironment, sensed via specialized AND gate equipment and second via tumor antigens that activate the chimeric antigen receptor. Thus, the CARTELTM ensures not to harm any of the healthy cells they are sworn to protect.