Somatic hypermutation

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The introduction of mutations into the antibody genes of a maturing B cell is called somatic hypermutation . It is an important step in the adaptive immune system . With the help of the enzyme Activation Induced Cytidine Deaminase (AID or AICDA), random changes in the DNA occur . AID deaminates cytosine to uridine in single-stranded DNA. The enzyme UNG removes uracil and creates an abasic site. A single strand break is generated there by APE1. In some cases this leads to an increased affinity of the antibodies for their antigen . By means of selection, those cells are chosen which best bind the antigen and can thus fight it most effectively. The remaining cells perish. This process, which in the germinal centers of secondary lymphoid organs ( spleen , lymph nodes takes place), it allows the body to produce a variety of different antibodies, and thus at the in the course of an immune evasion changing pathogens adapt well as the affinity of the antibodies for the Increase antigen.