A scientist who won the Nobel prize for medicine on Monday used his own discoveries to treat himself for cancer, but died of the disease just days before he could be told of the award.

Calling it bittersweet news, colleagues of Canadian-born Ralph Steinman at New York's Rockefeller University said he had prolonged his own life with a new therapy based on his prize-winning research into the body's immune system.

The 68-year-old physician, who joked last week with his family about hanging on until the annual prize declaration, died on Friday after a four-year battle with pancreatic cancer -- a fact the Nobel committee was not told until hours after it announced the 2011 award was shared by Steinman and two others.

He never knew his life's work had been crowned with the highest accolade science can bestow, becoming the first person in half a century to win a posthumous Nobel prize -- after a day of consternation in Stockholm, where the Nobel rules have long insisted, in principle, on recognising only the living.

We wanted him to be here for this, said his daughter Alexis Steinman, 34. We were like 'OK Dad, I know things aren't going well but the Nobel, they are going to announce it next Monday'. And he's like: 'I know I have got to hold out for that. They don't give it to you if you have passed away.

'I got to hold out for that.'

The Nobel Committee spent the morning calling Steinman to offer the traditional congratulations only to discover they faced a unique situation. After anguished consultations on the fate of the prize, and money worth three quarters of a million dollars, they decided it would go to Steinman's heirs.

Two other pioneers whose work on the immune system has also driven ground-breaking possibilities for curbing infections and cancers, American Bruce Beutler and Jules Hoffman from France, shared the other half of the 10 million-crown prize.

Steinman, whose research contributed to the launch last year of the first approved vaccine to kill tumours, was working until his final days, colleagues said.

BITTERSWEET NEWS

Admitted to hospital last Sunday, he lost consciousness on Thursday and died surrounded by family the following day. But Rockefeller University president Marc Tessier-Lavigne said his staff only heard of his death from the family about half an hour after news of the Nobel prize came out from Sweden.

Nobel Committee secretary general Goran Hansson told Reuters: I am, of course, saddened that Dr Steinman could not receive this news and feel that happiness.

He was a great scientist.

After examining a rule which bars giving the prize to the dead, and a second which says a laureate nonetheless keeps the prize if they die between the announcement and the award ceremony held some weeks later, the committee said it found the latter rule to be more fitting to Steinman's case.

The Nobel Prize shall not deliberately be awarded posthumously. However, the decision to award the Nobel Prize to Ralph Steinman was made in good faith, based on the assumption that the Nobel laureate was alive, the committee said.

His university said: Steinman ... was diagnosed with pancreatic cancer four years ago, and his life was extended using a dendritic-cell based immunotherapy of his own design.

Those cells, which the Montreal-born Steinman discovered in the 1970s, are vital to the attack the body launches on tumours and infections if they breach its first line of immune defence.

The other prizewinners, Beutler and Hoffmann, studied the first stages of the body's immune responses in the 1990s.

Lars Klareskog, who chairs the prize panel, said: I am very excited about what these discoveries mean. In particular they may offer ways to tackle antibiotic-resistant microbes.

Beutler, 53, is based at the Scripps Research Institute in La Jolla, California. Luxembourg-born Hoffmann, 70, conducted much of his work in Strasbourg.

SELF-DEFENCE

The work of all three prizewinners 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 tumours.

Better understanding of the complexities of the immune system has also given clues to treating inflammatory diseases, such as rheumatoid arthritis, in which the body's defence system goes haywire and ends up attacking its own tissues.

Beutler told Reuters his work might lead to new treatments for inflammatory and auto-immune disease, and possibly new treatments for other kinds of diseases as well.

In the United States, the Leukemia and Lymphoma Society said the trio's work formed the foundation of immunotherapy which holds great promise for the cancer community.

Beutler and Hoffmann discovered in the 1990s that receptor proteins act as a first line of defence, innate immunity, by recognising bacteria and other microorganisms. Steinman's work, explained how, if required, dendritic cells in the next phase, adaptive immunity, kill off infections that break through.

The research ultimately led to the launch of the first therapeutic cancer vaccine last year, Dendreon's Provenge, which treats men with advanced prostate cancer.

It was unclear how Steinman had treated his own pancreatic cancer -- a notoriously deadly form of the disease. The development of treatments from research can take many years. Former student Michel Nussenzweig said Steinman's discovery was only now reaching that stage after a particular wait.

No one believed it for a really long time, Nussenzweig said of the work on cells. His dream was to use his discovery to develop vaccines and it's a dream that's pretty close.

Medicine is usually the first of the Nobel prizes awarded each year. They were first awarded in 1901 using a bequest from dynamite inventor Alfred Nobel.

The only previous posthumous awards were to Swedes: poet Erik Axel Karlfeldt, for literature, in 1931; and U.N. chief Dag Hammarskjold, given the 1961 peace prize weeks after dying in a plane crash while on a peacemaking mission in Africa.