Three scientists have been announced as winners of the 2011 Nobel Medicine Prize for work on the immune system, however the jury has since learned that one of the winners died just days ago.
The winners were Bruce Beutler of the US, Luxembourg-born Jules Hoffmann, who is a naturalised French citizen, and Ralph Steinman of Canada, who it was discovered had died on 30 September.
"This year's Nobel laureates have revolutionised our understanding of the immune system by discovering key principles for its activation," the jury said in a statement.
The three were lauded for their work on the body's complex defence system in which signalling molecules unleash antibodies and killer cells to respond to invading microbes.
Understanding this throws open the door to new drugs and also tackling immune disorders such as asthma, rheumatoid arthritis and Crohn's disease, in which the body mysteriously attacks itself.
"Their work has opened up new avenues for the development of prevention and therapy against infections, cancer and inflammatory diseases," the jury said.
Several hours after the announcement, as the Nobel jury was still struggling to reach the candidates, New York's Rockefeller University, where Mr Steinman headed the Centre of Immunology and Immune Diseases, said the laureate had died four days ago of pancreatic cancer, at the age of 68.
The Nobel Prize cannot be awarded posthumously, but Mr Steinman's death was not known until his university tried to contact him today about his win.
"The news is bittersweet, as we also learned this morning from Ralph's family that he passed a few days ago after a long battle with cancer," the university said in a statement.
It said the laureate had been diagnosed with pancreatic cancer four years ago and "his life was extended using a dendritic-cell based immunotherapy of his own design".
Committee secretary Goeran Hansson told journalists that no new winners would be named however he was unsure how the prize would now be awarded.
"How it will be done in practice to hand out the prize is what we will have to investigate," he said, adding "we are examining the rules."
Mr Beutler, 55, and Mr Hoffmann, 70, who just a few days ago received a joint Shaw prize in Hong Kong, were meanwhile set to share one half of the 10m Swedish kronor (€1.08m) Nobel prize.
They discovered receptor proteins that activate the first step in the body's immune system.
Known as the innate response, it acts like a blunt instrument, seeking to swiftly block an assault through inflammation.
Mr Steinman won the other half of the prize for work on the second, slower line of defence, known as the adaptive response.
In 1973, he discovered a new type of cell, the dendritic cell, and demonstrated its role in unleashing T cells - the "heavy artillery" of the immune system.
T cells are part of an immunological memory, enabling a faster and powerful mobilisation of defences the next time the same microorganism attacks.
Mr Steinman, who also won the 2007 Lasker Prize for his work, showed that the body's immune system was able to attack harmful microorganisms while staying clear of the body's own molecules.
