The immunoglobulin switch region, also known as the isotype switch region, is a segment of a gene that is responsible for regulating the class switching of immunoglobulin molecules. Class switching is an essential process in the immune system, whereby B lymphocytes change the type of antibody they produce, without altering their antigen specificity.
Located in the Immunoglobulin heavy chain (IgH) locus on chromosome 14 in humans, the switch region consists of repetitive DNA sequences that flank each constant region gene segment. These sequences are highly conserved and play a crucial role in the rearrangement and recombination events that occur during class switching.
During B cell development, the switch region undergoes DNA recombination events mediated by enzymes called activation-induced cytidine deaminases (AID). AID introduces mutations in the switch region, resulting in DNA double-strand breaks. These breaks facilitate the deletion of intervening DNA sequences and the recombination of variable region exons with a constant region exon of a different immunoglobulin isotype.
The switch region is crucial for diversifying the repertoire of antibodies present in the immune system. By undergoing class switching, B cells can produce different antibody isotypes, such as IgG, IgA, or IgE, each with distinct effector functions. This allows the immune system to mount appropriate immune responses against different types of pathogens and antigens.
In summary, the immunoglobulin switch region is a specialized DNA segment that serves as a control center for the class switching of immunoglobulins, contributing to the versatility and adaptability of the immune response.
