The 2011 Nobel Prize for Medicine has been awarded jointly to three researchers for their work related to the immune system.

The prize has been divided, with one half going jointly to Bruce A. Beutler and Jules A. Hoffmann for their discoveries concerning the activation of innate immunity and the other half to Ralph M. Steinman for his discovery of the dendritic cell and its role in adaptive immunity.

The three scientists together have “revolutionized our understanding of the immune system,” according to a statement from the Nobel Assembly at the Karolinska Institute in Stockholm, through research unlocking secrets about how people's bodies fight off diseases.

Beutler, an American currently at the Scripps Research Institute in California and Jules Hoffmann, a Luxembourg-born scientist who spent most of his career in France, discovered receptor proteins that can recognize such micro-organisms and activate innate immunity, the first step in the body's immune response.

Steinman, a Canadian affiliated with Rockefeller University in New York, discovered the dendritic cells of the immune system and their unique capacity to activate and regulate adaptive immunity, the later stage of the immune response during which micro-organisms are cleared from the body.

The discoveries provided novel insights into the activation and regulation of our immune system, according to the Nobel Committee.

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