Over 100 years ago a hypothesis was formulated that the individual’s immune system had the capability of detecting and destroying cancerous cells. At the start of the 1970s, T cells (a special kind of defence cell) were discovered, as was their connection to specific immunological defence. Today, modern tumour immunology plays a decisive role in cancer therapy. In 2011 a breakthrough was achieved with the successful application of a medication (ipilimumab) that had a new mechanism for treating cancer, namely checkpoint inhibitors, used in the treatment of advanced melanoma (malignant). New approaches in terms of molecular mechanisms were also discovered. Today, certain cancers such a lung, head and neck, and bladder carcinoma are treated using similar immune therapy.