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Clonal selection is the process by which the immune system produces B and T lymphocytes to fight off harmful antigens. Niels Jerne proposed that humans are born with templates for all necessary antibodies. When an antigen invades the body, the lymphocyte with the correct antibody pattern is activated and multiplies, creating effector and memory cells. Memory cells play an important role in the secondary immune response.
Clonal selection is an important immunological process that determines which B and T lymphocytes, types of white blood cells, will be produced in large quantities. It is through this process that our body fights off antigens – substances that it considers harmful to it. Niels Jerne, a Danish immunologist, provided the basis for the theory of clonal selection in 1955. Prior to Jerne’s theory, it was a common belief that our bodies are stimulated to produce a specific antibody when a foreign substance enters them.
Jerne proposed that humans are born with the necessary templates for all the antibodies the immune system would ever need to produce. Each person’s entire immunological repertoire of antibodies is developed in utero. David Talmage and F. McFarlane Burnet independently outlined the process of clonal selection in 1957.
Each lymphocyte has a unique antibody on its surface. Antibodies are proteins that bind to harmful antigens to neutralize them. If the immature cells have antigen receptors that match any of the tissues in the body, then those particular cells are destroyed.
Clonal selection is part of the primary immune response. A primary immune response is elicited when a new antigen invades the body. Traveling through the circulatory system, the antigen will inevitably encounter the lymphocyte that has the correct antibody pattern.
When the lymphocyte and the antigen connect, a chemical change is triggered. The lymphocyte is activated, causing it to multiply rapidly and create many clones of itself. This is how the process was called clonal selection. The body will continue to produce prolific quantities of the selected lymphocyte cells in an attempt to inhibit and prevent infection.
During multiplication, the lymphocyte creates two main types of cells: effector cells and memory cells. Effector cells, or B and T lymphocytes, are short-lived cells created for immediate immunological defense. Memory cells are not active during the primary immune response, but will play an important role during a secondary immune response.
Effector cells are cells produced to perform a specific function in response to a particular stimulus. In this case, the cells are produced in response to a specific antigen. Effector B cells are responsible for the production of antibodies.
T cells are divided into helper T cells and cytotoxic cells. Helper cells produce cytokines. Cytokines are protein molecules that are produced when an antigen is detected to aid in cell-to-cell communication and immune response. Cytotoxic T cells destroy cells that have been infected with the antigen in question.
Some of the B and T cells created will become memory cells. The second time an antigen enters the body it triggers a secondary immune response. Memory cells created during clonal selection reactivate and mount a response. Each time an immune system is exposed to an antigen, the number of memory cells created becomes more and more, thus reducing the effects of an antigen.
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