Canada-born Ralph M. Steinman, of New York's Rockefeller University, who was honored with the Nobel Prize for Medicine for his groundbreaking work on the immune system, died of cancer just days before he could be told of the award.

After a four-year battle with pancreatic cancer, Steinman died Friday. The Nobel committee, though, was not aware of this. It is reported his life was prolonged with treatments based on his own research into the body's immune system.

The Nobel is not awarded posthumously, but there is also a rule that a laureate can keep the prize if he dies between the announcement and the award ceremony held some weeks later. The Nobel 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.

The prize has been divided, with one half going jointly to American Bruce A. Beutler and Frenchman Jules A. Hoffmann for their discoveries concerning the activation of innate immunity and the other half to Steinman for his discovery of the dendritic cell and its role in adaptive immunity, according to an earlier announcement by the committee.

Steinman 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.

Beutler, currently at the Scripps Research Institute in California, and Jules Hoffmann, a Luxembourg-born scientist who has 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.

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

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