Question

Briefly describe Somatic Hypermutation and Affinity Maturation processes. Include in your answer:

a) what each of these processes is,

b) what cells and genes are directly affected by these processes,

c) where these processes occur in the body

d) what is the significance of these processes to the immune response?

Answer 1

Somatic hypermutation

Somatic hypermutation (or SHM) is a cellular mechanism by which the immune system adapts to the new foreign elements that confront it (e.g. microbes), as seen during class switching. It allows B cells to mutate the genes that they use to produce antibodies. This enables the B cells to produce antibodies that are better able to bind to bacteria, viruses and other infections. It occurs in the periphery in germinal center follicles of secondary lymphoid organs. Antibodies created by this process can have markedly increased affinities for self-antigens.

Affinity maturation

B cells mutate and are presented to the antigen, only those that recognize the antigen with high affinity will survive while B cells producing antibodies with low affinity will be eliminated. This process is known as affinity maturation.Affinity maturation is the process by which TFH cell-activated B cells produce antibodies with increased affinity for antigen during the course of an immune response. With repeated exposures to the same antigen, a host will produce antibodies of successively greater affinities.Affinity maturation primarily occurs on surface immunoglobulin of germinal center B cells and as a direct result of somatic hypermutation (SHM) and selection by TFH cells.