Three scientists who uncovered key secrets of how the body's immune system works have won the 2011 Nobel prize for medicine or physiology.
Sweden's Karolinska Institute said in a statement that the prize went to US scientist Bruce Beutler, Luxembourg-born Jules Hoffmann, based in France, and Canadian-born Ralph Steinman, based in the United States.
Dr Steinman (68), died on Friday, before the prize was announced.
"This year's Nobel Laureates have revolutionised our understanding of the immune system by discovering key principles for its activation," the institute said.
Dr Beutler and Dr Hoffmann shared one half of the prize of 10 million Swedish crowns (€1.08 million) and Dr Steinman was awarded the other half.
Rockefeller University, where Dr Steinman was based, said in a statement that he died of cancer last week. "He was diagnosed with pancreatic cancer four years ago, and his life was extended using a dendritic-cell based immunotherapy of his own design," the New York-based university said in a statement posted on its website.
The work of the three scientists has been pivotal to the development of improved types of vaccines against infectious diseases and novel approaches to fighting cancer. The research has helped lay the foundations for a new wave of so-called "therapeutic vaccines" that stimulate the immune system to attack tumours.
They discovered receptor proteins that can recognise microorganisms attacking the body and which activate "innate immunity", the first step in the body's immune response, the institute said.
"Ralph Steinman discovered the dendritic cells of the immune system and their unique capacity to activate and regulate adaptive immunity, the later stage of the immune response during which microorganisms are cleared from the body," it added.
The award citation said scientists had long been researching the immune response by which man and other animals defend themselves against attack by bacteria and other microorganisms.
Better understanding of the complexities of the body's immune system has also provided clues for treating inflammatory diseases, such as rheumatoid arthritis, where the components of the self-defence system end up attacking the body's own tissues.
Medicine is traditionally the first of the Nobel prizes awarded each year. Prizes for achievements in science, literature and peace were first awarded in 1901 accordance with the will of dynamite inventor and businessman Alfred Nobel.
Last year’s medicine award went to British professor Robert Edwards for fertility research that led to the first test tube baby.
Today's announcement will be followed in the coming days by announcements for prizes in chemistry, physics, literature, peace and economics.
Agencies