Honjo, a Japanese immunologist, discovered a protein on immune cells that also operates as a brake, but with a different mechanism of action.
Allison's work, much of it done at the University of California-Berkley, changed that by proving the immune system could identify tumor cells and act against them.
Their work centers on harnessing the immune system to arrest the development of cancer. "The immune system was neglected because there was no strong evidence it could be effective", said Nadia Guerra, head of a cancer laboratory at Imperial College London. A driving motivation for scientists is simply to push the frontiers of knowledge. And more recently, scientists have found that combining the two targets can be even more effective in cancer treatment, particularly in combating melanoma.
Last year, USA geneticists Jeffrey Hall, Michael Rosbash and Michael Young were awarded the medicine prize for their research on the role of genes in setting the "circadian clock" which regulates sleep and eating patterns, hormones and body temperature.
Awards in physics, chemistry, peace and economics will follow. The Nobel prize can only be awarded to individuals, but it is important to remember that others would have been involved in the discoveries.