Clonal Selection Theory

Clonal selection theory, also known as Burnet's theory, is a theory of immunity proposed by Australian immunologist Frank Macfarlane Burnet in 1959.

According to this theory, the immune system consists of many lymphocytes, each of which carries a unique antigen recognition receptor on its surface. These receptors are generated randomly through somatic mutations in the genes encoding the receptor components.

When a lymphocyte collides with a foreign antigen, clonal proliferation and differentiation occurs of those few cells whose receptors specifically bind to this antigen. This process is called clonal selection. Thus, the immune system selects the few lymphocytes that can recognize a particular antigen and multiplies them to fight the infection.

Clonal selection theory explained the mechanism of specificity of the immune response and significantly advanced the understanding of the functioning of the immune system. It remains a fundamental concept in immunology.