Ig somatic hypermutation (IgSHM) refers to a biological process that occurs within the immune system, specifically in the maturation of B lymphocytes or B cells. B cells are a type of white blood cell responsible for producing antibodies that recognize and neutralize foreign substances in the body. During the process of IgSHM, the DNA sequences that code for the antibodies on the surface of B cells undergo random mutations.
These mutations enable the diversification of antibody specificity, enhancing the immune response to a wider range of antigens. IgSHM mainly occurs in the variable region of the immunoglobulin genes, where the coding sequence of antibodies differs between different B cells.
The mechanism of IgSHM involves the activation-induced cytidine deaminase (AID) enzyme, which initiates the unwinding and deamination of cytosine bases within the DNA sequence. This deamination leads to the conversion of cytosine to uracil, triggering a strand break in the DNA.
The repair process of these strand breaks is error-prone, leading to the introduction of random nucleotide changes during the repair. This subsequently alters the amino acid sequence of the antibody, resulting in a diverse repertoire of B cells that produce antibodies with varying affinities and specificities.
IgSHM plays a crucial role in the adaptive immune response, allowing B cells to generate antibodies that can recognize and bind to a multitude of foreign antigens. This process is particularly important in the generation of high-affinity antibodies during viral infections, vaccines, and immune responses against cancer cells.
