Clonal selection

Clonal selection
Clonal selection of lymphocytes: 1) A hematopoietic stem cell undergoes differentiation and genetic rearrangement to produce 2) immature lymphocytes with many different antigen receptors. Those that bind to 3) antigens from the body's own tissues are destroyed, while the rest mature into 4) inactive lymphocytes. Most of these will never encounter a matching 5) foreign antigen, but those that do are activated and produce 6) many clones of themselves.

The clonal selection hypothesis has become a widely accepted model for how the immune system responds to infection and how certain types of B and T lymphocytes are selected for destruction of specific antigens invading the body.


Four predictions of the clonal selection hypothesis

  • Each lymphocyte bears a single type of receptor with a unique specificity (by V(D)J recombination).
  • Receptor occupation is required for cell activation.
  • The differentiated effector cells derived from an activated lymphocyte will bear receptors of identical specificity as the parental cell.
  • Those lymphocytes bearing receptors for self molecules will be deleted at an early stage.

Early work

In 1954, immunologist Niels Jerne put forward a hypothesis which stated that there is already a vast array of lymphocytes in the body prior to any infection. The entrance of an antigen into the body results in the selection of only one type of lymphocyte to match it and produce a corresponding antibody to destroy the antigen.

This selection of only one type of lymphocyte results in it being cloned or reproduced by the body extensively to ensure there are enough antibodies produced to inhibit and prevent infection.

Further work

Australian immunologist Frank Macfarlane Burnet with input from David W. Talmage worked on this model, and was the first to name it "clonal selection theory." Burnet explained immunological memory as the cloning of two types of lymphocyte. One clone acts immediately to combat infection whilst the other is longer lasting, remaining in the immune system for a long time, which results in immunity to that antigen. In 1958, Sir Gustav Nossal and Joshua Lederberg showed that one B cell always produces only one antibody, which was the first evidence for clonal selection theory.[1]

Theories supported by clonal selection

Burnet and Peter Medawar worked together on understanding immunological tolerance, a phenomenon also explained by clonal selection. This is the organism’s ability to tolerate the introduction of cells without an immune response as long as this occurs early in the organism’s development. There are a vast number of lymphocytes occurring in the immune system ranging from cells which are tolerant of self tissue to cells which are not tolerant of self tissue. However, only cells that are tolerant to self tissue will survive the embryonic stage. If non-self tissue is introduced, the lymphocytes which develop will be the ones which included the non-self tissues as self tissue.

In 1949 Burnet proposed that under certain circumstances, tissues could be successfully transplanted into foreign recipients. This work has led to a much greater understanding of the immune system and also great advances in tissues transplantation. Burnet and Medawar shared the Nobel Prize for physiology and medicine in 1960.

In 1974 Niels Kai Jerne proposed that the immune system functions as a network, that is regulated via interactions between the variable parts of lymphocytes and their secreted molecules. Immune network theory is firmly based on the concept of clonal selection. Jerne won the Nobel Prize for medicine or physiology in 1984, largely for his contributions to immune network theory.

See also


  1. ^ Nossal, G. J. V. & Lederberg, J. 1958. Antibody production by single cells. Nature 181:1419-1420

External links

Animation of clonal selection from the Walter & Elisa Hall institute.

Wikimedia Foundation. 2010.

Игры ⚽ Нужен реферат?

Look at other dictionaries:

  • clonal selection — noun (biology) In a young mammal, the method of immunoglobulin production ensuring that there is a large lymphocyte population with a wide variety of antigen binding sites, so that when a foreign antigen binds to a lymphocyte it will stimulate… …   Useful english dictionary

  • clonal selection — The process whereby one or more clones, ie. cells expressing a particular gene sequence are selected by naturally occurring processes from a mixed population. Generally the clonal selection is for general expansion by mitosis, particularly with… …   Dictionary of molecular biology

  • clonal selection theory — clonal selection theory. См. клонально селекционная теория. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • Clonal Selection Algorithm — In Artificial immune systems, Clonal selection algorithms are a class of algorithms inspired by the clonal selection theory of acquired immunity that explains how B and T lymphocytes improve their response to antigens over time called affinity… …   Wikipedia

  • clonal selection theory — a modification of the natural selection theory (q.v.): there are in each adult several million clones of antibody producing cells, each programmed to make antibody of a single specificity and bearing cell surface receptors capable of reacting… …   Medical dictionary

  • clonal selection — The production of a population of plasma cells all producing the same antibody in response to the interaction between a B lymphocyte producing that specific antibody and the antigen bound by that antibody. See: primary immune response, secondary… …   Glossary of Biotechnology

  • Clonal — may refer to in Immunology Clonal deletion, a process by which B cells and T cells are deactivated before act significantly upon specific antigens Clonal selection theory, a model for how the immune system responds to infection Clonal anergy, a… …   Wikipedia

  • clonal deletion theory — a theory of immunologic tolerance to self antigens according to which “forbidden clones” of immunocytes, those reactive with self antigens, are eliminated on contact with antigen during fetal life. The terms “clonal abortion,” “clonal… …   Medical dictionary

  • clonal — ● clonal, clonale, clonaux adjectif Qui concerne le clone. clonal, ale, aux [klɔnal, o] adj. ÉTYM. 1961; de clone. → Clone. ❖ ♦ Biol. Relatif à un clone, aux clones, au clonage. || Sélection clo …   Encyclopédie Universelle

  • Selección clonal — Teoría de Selección Clonal Esta teoría postula que cada antígeno estimulará a aquel linfocito o grupo de linfocitos que poseen en su membrana receptores capaces de reconocer y unirse específicamente a él y que como consecuencia se producía su… …   Wikipedia Español

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”