NOBEL 2011/ Medicine: how our body fights off invaders

Dying three days before winning the Nobel Prize: this is what happened, because of some mysterious plan, to Ralph M. Steinman, the sixty-eight year old biochemist who, by that same plan, was able to prolong his existence on earth despite suffering from pancreatic cancer by using his own discovery. In 1973, he discovered a new type of cell, dendritic cells, and hypothesized about their role in the adaptive immune system. He has now received the highest accolade for this discovery, but will be unable to receive the reward in person in December in Stockholm.

The other two winners of the Nobel Prize for medicine and physiology will be there, however. Both the Luxembourg Jules Hoffmann and the American Bruce Beutler will be honored "for their discoveries concerning the mechanisms of activation of innate immunity". The first studied the defense mechanisms in fruit flies and understood that certain mutants died because they were not able to develop an adequate immune defense. The second showed that fruit flies and mammals use similar molecules to activate the innate immune system.

These were three key steps in the path to knowledge about our immune system, that collection of sophisticated mechanisms that defends the body from attack by potentially hostile "foreign invaders”, such as viruses, bacteria or other harmful substances that may damage the organism, sometimes permanently.

Ilsussidiario.net spoke with Maria Grazia Sabbadini, Professor of Internal Medicine at the University Vita-Salute San Raffaele and the Head of the General Practice Unit of Immunology, Rheumatology and Allergology at the Scientific Institute of the San Raffaele Hospital in Milan.

First of all, can you explain what innate immunity is?
Innate immunity is the most ancient in evolutionary history and consists in a series of cells such as monocytes, macrophages and also dendritic cells, which are equipped with receptors that recognize certain groups of molecules present in pathogens but not in the interior of the body. Therefore, they make up the first group of barriers that recognize the presence of foreign cells and thus give the body a warning signal of danger, which activates a variety of immune defenses.

Their characteristic is that they are immediate, and they do not confuse external and internal molecules. However, they lack the ability to replicate themselves rapidly in order to maintain their abilities over time, while bacteria multiply extremely quickly.

And the adaptive immune system?
The innate immune system reconnects to the adaptive, where dendritic cells collect pathogens dendritic cells, dismantle them and direct them towards the lymphatic stations where there is a continuous passage of lymphocytes, each with a different receptor with the ability to read a large number of different molecules and to recognize the antigen in question.