Professor Hans-Gustaf Ljunggren (R) of Karolinska Institute announces the 2011 Nobel Physiology or Medicine laureates during a news conference in Stockholm Oct 3, 2011. [Photo/Agencies]

STOCKHOLM - Three scientists who unlocked key elements of how the body's immune system works won the 2011 Nobel Prize in medicine on Monday.

US immunologist Bruce Beutler and French biologist Jules Hoffmann, for their discoveries concerning the activation of innate immunity, shared the award with Canadian-born Ralph Steinman, who died last week before the award was announced. He was honored for his discovery of the dendritic cell and its role in adaptive immunity.

"This year's Nobel laureates have revolutionized our understanding of the immune system by discovering key principles for its activation," the award panel at Sweden's Karolinska Institute said in a statement in Stockholm.

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 "therapeutic vaccines" that stimulate the immune system to attack tumors.

A better understanding of the complexities of the immune system has also given 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.

Lars Klareskog, who chairs the prize-giving Nobel Assembly, said: "I am very excited about what these discoveries mean. I think that we will have new, better vaccines against microbes and that is very much needed now with the increased resistance against antibiotics."

Annika Scheynius, a professor of clinical allergy research and a member of the panel, said these discoveries will "definitely improve the health of patients with cancer, inflammatory diseases, auto-immune diseases, and asthma."

Beutler, 53, who is based at the Scripps Research Institute in La Jolla, California, will share half the 10 million Swedish crowns ($1.46 million) of prize-money with Luxembourg-born Hoffmann, 70, who conducted much of his work in Strasbourg. The rest was to go to Steinman, 68, from Rockefeller University in New York.

Medicine, or physiology, is usually the first of the Nobel prizes awarded each year. The winners of the physics prize will be announced on Tuesday, to be followed by those for chemistry on Wednesday, literature on Thursday, peace on Friday and economics next Monday.

Reuters