Niels K. Jerne | Biography

Niels Kaj (sometimes transliterated Kai) Jerne was born on 23 December 1911, in London, England, to Danish parents Else Marie Lindberg and Hans Jessen Jerne. The family moved to the Netherlands at the beginning of World War I. Jerne earned his baccalaureate in Rotterdam in 1928 and studied physics for two years at the University of Leiden. Twelve years later, he entered the University of Copenhagen to study medicine, receiving his doctorate in 1951 at the age of 40. From 1943 until 1956 he worked at the Danish State Serum Institute, conducting research in immunology.

In 1955, Jerne traveled to the United States with noted molecular biologist Max Delbrück to become a research fellow at the California Institute of Technology at Pasadena. The two worked closely together, and it was not until his final two weeks at the Institute that Jerne completed work on his first major theory--on selective Max Delbrück formation. At this time, scientists believed that specific antibodies (molecules that defend the body from infection) do not exist until an antigen (any substance originating outside the body such as a virus) is introduced and acts as a template from which cells in the immune system create the appropriate antibody to eliminate it. Jerne's theory postulated instead that the immune system inherently contains all the specific antibodies it needs to fight specific antigens; the appropriate antibody, one of millions that are already present in the body, attaches to the antigen, thus neutralizing or destroying the antigen and its threat to the body.

In 1960, Jerne left his research in immunology to became chief medical officer with the World Health Organization in Geneva, Switzerland, where he oversaw the departments of biological standards and immunology. From 1960 to 1962, he served on the faculty at the University of Geneva's biophysics department.

From 1962 to 1966, Jerne was professor of microbiology at the University of Pittsburgh in Pennsylvania. During this period he developed a method, now known as the Jerne plaque assay, to count antibody-producing cells by first mixing them with other cells containing antigen material, causing the cells to produce an antibody that combines with red blood cells. Once combined, the blood cells are then destroyed, leaving a substance called plaque surrounding the original antibody-producing cells, which can then be counted. Jerne became director of the Paul Ehrlich Institute, in Frankfurt, Germany, in 1966, and, in 1969, established the Basel Institute for Immunology in Switzerland, where he remained until taking emeritus status in 1980.

In 1971, Jerne unveiled his second major theory, which deals with how the immune system identifies and differentiates between self molecules (belonging to its host) and nonself molecules (invaders). Noting that the immune system is specific to each individual, immunologists had concluded that the body's self-tolerance cannot be inherited and is therefore learned. Jerne postulated that such immune system "learning" occurs in the thymus, an organ in the upper chest cavity where the cells that recognize and attack antigens multiply, while those that could attack the body's own cells are suppressed. Over time, mutations among cells that recognize antigens increase the number of different antibodies the body has at hand, thereby increasing the immune system's arsenal against disease.

Jerne introduced what is considered his most significant work in 1974--the network theory, wherein he proposed that the immune system is a dynamic self-regulating network that activates itself when necessary and shuts down when not needed. At that time, scientists knew that the immune system contains two types of immune system cells, or lymphocytes: B cells, which produce antibodies, and T cells, which function as "helpers" to the B cells by killing foreign cells, or by regulating the B cells either by suppressing or stimulating their antibody producing activity. Further, antibody molecules produced by the B cells also contain antigen-like components (idiotypes ) which can attract another antibody (anti-idiotype), allowing one antibody to recognize another antibody as well as an antigen. Jerne's theory expanded on this knowledge, speculating that a delicate balance of lymphocytes and antibodies and their idiotypes and anti-idiotypes exists in the immune system until an antigen is introduced. The antigen, he believed, replaces the anti-idiotype attached to the antibody. The immune system then senses the displacement and, in an attempt to find the anti-idiotype a "mate," produces more of the original antibody. This chain-reaction strengthens the body's immunity to the invading antigen.

Jerne shared the 1984 Nobel Prize for medicine or physiology with Cesar Milstein and Georges J. F. Köhler for his body of work that explained the function of the immune system

Jerne retired to southern France with his wife, Ursula Alexandra Kohl, whom he married in 1964; the couple had two sons. A citizen of both Denmark and Great Britain, Jerne received honorary degrees from American and European universities, was a foreign honorary member of the American Academy of Arts and Sciences, a member of the Royal Danish Academy of Sciences, and won, among other honors, the Marcel Benorst Prize in 1979 and the Paul Ehrlich Prize in 1982. Jerne died on 7 October 1994 at his home in Pont du Gard, southern France.