Cellular Basis of Antibody Diversity: Clonal Selection

The specificity of humoral immune responses relies on the huge DIVERSITY of antigen combining sites present in antibodies, diversity which is generated in an antigenindependent fashion. The process by which antigen (during an immune response) stimulates the clonal expansion and differentiation of antibody-forming cells of predetermined specificity is known as CLONAL SELECTION. The basic principles of clonal selection are illustrated in this chapter by two classic experiments, and are applied to our understanding of some of the fundamental features of the adaptive immune response, namely TOLERANCE, MEMORY and AFFINITY MATURATION, as well as the presence of NATURAL ANTIBODIES.