Clonal Selection

The clonal selection theory explains how the adaptive immune system is able to respond to an almost infinite diversity of antigen. One potential option for achieving such diversity would have been for the cells of the adaptive immune system to bear an almost infinite number of different receptors, each capable of recognizing a different feature shared by pathogen. This would however have been limiting in terms of the level of diversity that could be achieved given the finite amount of space on the cell surface. Instead, each cell expresses a single specific receptor, generated by a process of somatic recombination. On binding antigen, the cell is activated and produces progeny, all with the same specificity. This generates a clone of cells and is the basis of the clonal selection theory.


The clonal selection mechanism allows each individual to expand clones specific for the antigens to which they have been exposed. Self reactive cells are removed during development by a process of clonal deletion.


The basic principles and processes involved in clonal selection are that each cell bears a single type of receptor with a unique specificity. That activation of that cell is triggered by receptor binding to antigen. That the activated cell proliferates, creating a clone with exactly the same receptor specificity and that these clonal cells are then able to undertake the effector function of that cell. In addition, self reactive cells are removed during development.


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