<P> The theory states that in a pre-existing group of lymphocytes (specifically B cells), a specific antigen only activates (i.e. selection) its counter-specific cell so that particular cell is induced to multiply (producing its clones) for antibody production . This activation occurs in secondary lymphoid organs such as the spleen and the lymph nodes . In short the theory is an explanation of the mechanism for the generation of diversity of antibody specificity . The first experimental evidence came in 1958, when Gustav Nossal and Joshua Lederberg showed that one B cell always produces only one antibody . The idea turned out to be the foundation of molecular immunology, especially in adaptive immunity . </P> <P> The clonal selection theory can be summarised with the following four tenets: </P> <Ul> <Li> Each lymphocyte bears a single type of receptor with a unique specificity (by V (D) J recombination). </Li> <Li> Receptor occupation is required for cell activation . </Li> <Li> The differentiated effector cells derived from an activated lymphocyte will bear receptors of identical specificity as the parental cell . </Li> <Li> Those lymphocytes bearing receptors for self molecules will be destroyed at an early stage . </Li> </Ul> <Li> Each lymphocyte bears a single type of receptor with a unique specificity (by V (D) J recombination). </Li>

Describe the process of clonal selection. explain how effector cells and antibodies are produced