secondary antibody diversification

In secondary antibody diversification, a secondary repertoire of antibody diversity is generated after antigen encounter.

The enzyme activation-induced (cytidine) deaminase (AID) is currently considered the master regulator of secondary antibody diversification because it is involved in the initiation of three distinct immunoglobulin diversification processes:
● somatic hypermutation (SHM),
● class-switch recombination (CSR), and
● gene-conversion (GC).

Conversely, repeated exposures to the same antigen provokes greater antibody ligating affinity (specificity) in the antibody secreted by successive generations of plasma cells. Affinity maturation is achieved through somatic hypermutation and clonal selection.

Antibody diversification processes are paramount in protection against pathogens. Both somatic hypermutation and gene conversion adjust the affinity of pathogen-specific antibodies by altering sequences within antibody variable genes. Class-switch recombination (CSR) alters effector function of antibodies by switching the constant regions of antibody genes.

Activation-induced cytidine deaminase (AID) initiates each of these three processes by deaminating cytosines in deoxycytidines within antibody genes. Subsequently, a host of other DNA transacting factors either create new mutations or repair the DNA lesions introduced during these processes.

Tables  Fc receptors  Immune Cytokines  Immunoglobulins