Dr. Jean Dausset, Nobel laureate, 92

Dr. Dausset, who specialized in blood diseases, shared the Nobel for Physiology or Medicine with two researchers working in the United States, Baruj Benacerraf and George D. Snell, for work done over several decades. The Karolinska Institute in Sweden, which awards the prize, said their research showed why some people were better able to defend themselves against infection than others and why certain people were at risk for autoimmune diseases like rheumatoid arthritis or lupus.

Dr. Dausset’s findings transformed understanding of the immune system, Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases, said in a telephone interview Monday.

Dr. Dausset’s main achievement was demonstrating that molecules on the surface of cells, now called HLA antigens, determine an individual’s immune response. These antigens, which are genetically coded by a particular location on one chromosome, determine the body’s response to foreign tissue, for example. They set off production of disease-fighting antibodies and help the immune system distinguish between the body’s own cells and invaders.

The research made it possible for transplant surgeons to type cells to determine whether a body would accept or reject tissue from a donor. Since then, such tissue typing has been used widely for heart, liver and other transplants.

In addition to demonstrating the existence of these antigens in people, Dr. Dausset “elucidated the genetic factors regulating their formation,’’ the Karolinska Institute said.

Working with Dr. Felix T. Rapaport, Dr. Dausset carried out a series of experimental skin grafts that provided evidence that incompatibility of antigens worked against the graft’s survival.

Subsequently, to find out if the genetic factors were valid for all humans and not just particular groups, Dr. Dausset and his colleagues went to far-flung places to obtain blood samples from people of 54 racial and ethnic groups. They found that the genetic laws controlling the antigens were valid for all groups.

Jean Baptiste Gabriel Joachim Dausset was born in Toulouse, France, the son of a prominent physician. He earned a bachelor’s degree at the Lycee Michelet in Paris and enrolled in medical school at the University of Paris in the late 1930s. With World War II looming, he was drafted before he could complete his studies. After France fell to the German invasion in 1940, he went to North Africa and joined the Free French forces.

Before leaving, he gave his identity papers to a Jewish colleague at the Pasteur Institute, to help the man avoid persecution by the Nazis.

He participated in the liberation of France in 1944 and left the military in 1945.

Dr. Dausset held a number of teaching and research posts, including chief biologist for the Paris General Hospital System; chairman of the immunology department at the University of Paris, where he taught for many years; and professor at the College de France.