(Update: Rockefeller University in New York says Ralph Steinman, co-winner of this year's Nobel Prize in medicine, was diagnosed with pancreatic cancer four years ago and died on Sept. 30, three days before Monday’s announcement. Nobel Prizes are typically not given out posthumously. Nobel committee member Goran Hansson said the Nobel committee didn't know Steinman was dead when it chose him as a winner and was looking through its regulations.)
STOCKHOLM (AP) — Three scientists whose discoveries on the immune system opened up new avenues for prevention and treatment of infections, cancer and inflammations won the Nobel Prize in medicine on Monday.
American Bruce Beutler and French scientist Jules Hoffmann shared the 10 million-kronor ($1.5 million) award with Canadian-born Ralph Steinman, the Nobel committee at Stockholm Karolinska institute said.
Beutler and Hoffmann were cited "for their discoveries concerning the activation of innate immunity."
Steinman, 70, was honored for "his discovery of the dendritic cell and its role in adaptive immunity."
"Their work has opened up new avenues for the development of prevention and therapy against infections, cancer and inflammatory disease," the citation said.
Beutler and Hoffman discovered receptor proteins that can recognize bacteria and other microorganisms as they enter the body, and activate the first line of defense in the immune system.
Steinman discovered dendritic cells in the immune system, which help regulate the next stage of the immune system's response, when the invading microorganisms are purged from the body.
The trio's discoveries have enabled the development of new methods for treating and preventing diseases, including improved vaccines and in attempts to help the immune system to attack tumors, the committee said.
The medicine award kicked off a week of Nobel Prize announcements, and will be followed by the physics prize on Tuesday, chemistry on Wednesday, literature on Thursday and the Nobel Peace Prize on Friday. The winners of the economics award will be announced on Oct. 10.
The coveted prizes were established by wealthy Swedish industrialist Alfred Nobel -- the inventor of dynamite -- except for the economics award, which was created by Sweden's central bank in 1968 in Nobel's memory. The prizes are always handed out on Dec. 10, on the anniversary of Nobel's death in 1896.
Last year's medicine award went to British professor Robert Edwards for fertility research that led to the first test tube baby.