James P Allison and Tasuku Honjo were awarded the 2018 Nobel Prize in Physiology or Medicine for the development of a revolution in cancer therapy: immune checkpoint blockade. This is a truly well-deserved honor for both Allison and Honjo. The immune system has multiple levels of brakes, known as immune checkpoints, to negatively downregulate activation and function of T cells and other immune cells. Immune checkpoints are important mechanisms for preventing the immune system from attacking the host's own cells.