Stockholm: Three scientists on Monday shared the Nobel Medicine Prize for their ground-breaking work on the immune system which the jury said opened up new prospects for curing cancer and other diseases.

The laureates are Bruce Beutler of the United States, Jules Hoffmann of Luxembourg and Ralph Steinman of Canada.

"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 immunology – the body's complex defence system in which signalling molecules unleash antibodies and killer cells in response to invading germs and viruses.

Understanding this is a key to new drugs and also to easing immune disorders, such as asthma, rheumatoid arthritis and Crohn's disease.

"Their work has opened up new avenues for the development of prevention and therapy against infections, cancer and inflammatory diseases," the jury said.

Beutler and Hoffmann, who shared one half of the 10 million Swedish kronor (USD 1.48 million) prize, discovered receptor proteins that activate the first step in the body's immune response system.

Steinman, who won the other half, discovered the dendritic cells, allowing the immune system to identify and attack the harmful micro-organisms while staying clear of the body's own endogenous molecules.

They will receive their prize at a formal ceremony in Stockholm on December 10, the anniversary of prize founder Alfred Nobel's death in 1896.

2011 Nobel season commences

The 2011 Nobel season opens on Monday with the announcement in Stockholm of the Medicine Prize, to be followed over the course of a week by the awards for physics, chemistry, literature, economics and peace.

The Medicine Prize is scheduled to be announced at 1500 IST at the earliest.

The winner of the Nobel Peace Prize, perhaps the most watched of the prestigious awards, will be revealed Friday in Oslo, and the five-member Norwegian Nobel committee has a record 241 nominees to choose from, the list of which is kept a well-guarded secret.

Nobel watchers say however the nod could this year go to activists involved in the Arab Spring uprising, which led to the overthrow of autocratic regimes in Tunisia, Egypt and Libya and rattled the ones in Syria, Yemen and Bahrain.

If that were the case, among those mentioned as possible winners is Tunisian blogger Lina ben Mhenni, who chronicled her country's revolution on the Internet.

Another possibility is Israa Abdel Fattah of Egypt and the April 6th youth Movement that she co-founded with Ahmed Maher in 2008.

“The movement, which began on Facebook played a key role in maintaining the direction and non-violent character of the uprisings in Egypt,” said Kristian Berg Harpviken, the head of the Peace Research Institute of Oslo.

He also mentioned Google executive Wael Ghonim, "a principled non-violence activist" who was a central inspiration to the protests in Cairo's Tahrir Square.

Other names circulating are Afghan human rights activist Sima Samar, Russian human rights organization Memorial, Liberian activist Leymah Gbowee, Zimbabwean Prime Minister Morgan Tsvangirai, Germany's ex-chanceller Helmut Kohl and the European Union.

Last year the prize went to jailed Chinese dissident Liu Xiaobo.

For the other closely-watched prize, that for literature which last year went to Peruvian-Spanish author Mario Vargas Llosa, literary circles suggest the situation in the Middle East could also play a role in the Swedish Academy's choice, with Syrian poet Adonis tipped as a favourite.

In June, Adonis, whose real name is Ali Ahmed Said and who lives in France, published an open letter to Syrian President Bashar al-Assad in a Lebanese newspaper urging him to end the bloody repression.

Online betting site Ladbrokes tipped Adonis as the favourite on September 30, just ahead of Swedish poet Tomas Transtroemer.

Kenya's Ngugi wa Thiong'o, Somalia's Nuruddin Farah, Hungary's Peter Nadas, Korean poet Ko Un, Japan's Haruki Murakami, India's Vijaydan Detha and Australia's Les Murray also figure among the favourites for this year's Literature prize, which will most probably be announced on October 6 but could come any Thursday in October.