Illustration of the US immunologist James P. Allison (born 1948). Allison is best known for his work on T cells (a white blood cell of the immune system) and immune system tumour recognition. In the early 1980s he discovered the T cell antigen receptor, the protein the cells use to recognise foreign substances and cancerous cells. Further work showed that the molecule CD28 was required for T cell activation and that CD28 was regulated by an immune checkpoint molecule (CTLA-4) to prevent it attacking healthy cells. Some cancer cells take advantage of CTLA-4 to avoid detection by T cells. Allison showed that blocking CTLA-4 enhanced T cell response to cancers and lead to tumour shrinkage and developed the first immune checkpoint blockade therapy to treat cancer. Allison was awarded a share of the 2018 Nobel Prize in Physiology or Medicine for this work along with Tasuku Honjo.