Clonal selection

In immunology, clonal selection theory explains the functions of cells of the immune system (lymphocytes) in response to specific antigens invading the body. The concept was introduced by Australian doctor Frank Macfarlane Burnet in 1957, in an attempt to explain the great diversity of antibodies formed during initiation of the immune response.^[1][2] The theory has become the widely accepted model for how the human immune system responds to infection and how certain types of B and T lymphocytes are selected for destruction of specific antigens.^[3]

The theory states that in a pre-existing group of lymphocytes (both B and T cells), a specific antigen activates (i.e. selects) only its counter-specific cell, which then induces that particular cell to multiply, producing identical clones for antibody production. This activation occurs in secondary lymphoid organs such as the spleen and the lymph nodes.^[4] In short, the theory is an explanation of the mechanism for the generation of diversity of antibody specificity.^[5] The first experimental evidence came in 1958, when Gustav Nossal and Joshua Lederberg showed that one B cell always produces only one antibody.^[6] The idea turned out to be the foundation of molecular immunology, especially in adaptive immunity.^[7]