Microbiology and Immunology

WORLD OF MICROBIOLOGY AND IMMUNOLOGY Jerne, Niels K.

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Physicians in London, insisting that he first pass a test on the

theories of Hippocrates and Galen. Jenner refused to bow to

their demands, saying his accomplishments in conquering

smallpox should have qualified him for election. He was never

elected to the college. Jenner continued his medical practice,

as well as collecting fossils and propagating hybrid plants in

his garden, until his death from a stroke at the age of 73.

Nearly two centuries after Jenner’s experimental vacci-

nation of young James, the World Health Organization

declared endemic smallpox to be eradicated.

See alsoAntibody and antigen; Antibody formation and kinet-

ics; Immunity, active, passive and delayed; Immunity, cell

mediated; Immunity, humoral regulation

JJerne, Niels K.ERNE, NIELSK.(1911-1994)

Danish immunologist

Often considered the founder of modern cellular immunology,

Niels K. Jerne shared the 1984 Nobel Prize for medicine or

physiology with César Milsteinand Georges J. F. Köhler for

his body of work that explained the function of the immune

system, the body’s defense mechanism against disease and

infection. He is best known for three theories showing how

antibodies—the substances which protect the body from for-

eign substances such as virusesand poisons—are produced,

formed, and regulated by the immune system. His theories

were initially met with skepticism, but they later became the

cornerstones of immunological knowledge. By 1984, when

Jerne received the prize, colleagues agreed that he should have

been recognized for his important contributions to the field

much earlier than he was. Jerne’s theories became the starting

point from which other scientists, notably 1960 Nobel Prize

winner Frank MacFarlane Burnett, furthered understanding of

how the body protects itself against disease.

Niels Kaj (sometimes translated Kai) Jerne was born 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 forty. 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 fel-

low 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 antibody formation. At this time,

scientists accepted that specific antibodies do not exist until an

antigen—any substance originating outside the body (e.g., a

virus, snake venom, transplanted organs, etc.)—is introduced,

and acts as a template from which cells in the immune system

create the appropriate antibodyto eliminate it. Antigens and

antibodies have surface patches, called combining sites, with

distinct patterns. When an antibody and antigenwith comple-

mentary combining sites meet, they become attached, fitting

together like a lock and key. 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.

Not until some months after developing his theory did

Jerne shared it with Delbrück, who sent it to the Proceedings

of the National Academy of Sciencesfor publication. Jerne

later noted that his theory probably would have been forgot-

ten, except that it caught the attention of Burnett, leading him

to the development in 1959 of his clonal selectiontheory,

which built on Jerne’s hypothesis to show how specific anti-

body-producing cells multiply to produce necessary quantities

of an antigen’s antibody. The following year, Jerne left his

research in immunology to become chief medical officer with

the World Health Organizationin 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 microbiol-

ogy at the University of Pittsburgh in Pennsylvania. During

this period, he developed a method, now known as the Jerne

plaqueassay, to count antibody-producing cells by first mix-

ing 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, leav-

ing a substance called plaque surrounding the original anti-

body-producing cells, which can then be counted. Jerne

became director of the Paul EhrlichInstitute, in Frankfurt,

Germany, in 1966, and, in 1969, established the Basel Institute

for Immunology in Switzerland, where he remained until tak-

ing 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 mol-

ecules (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,

mutationsamong 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 regulat-

ing the B cells either by suppressing or stimulating their anti-

body producing activity. Further, antibody molecules

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