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Induced overexpression of AID in CH12F3-2 B lymphoma cells augmented class switching from IgM to IgA without cytokine stimulation. AID deficiency caused a complete defect in class switching and showed a hyper-IgM phenotype with enlarged germinal centers containing strongly activated B cells before or after immunization. AID-/- spleen cells stimulated in(More)
The activation-induced cytidine deaminase (AID) gene, specifically expressed in germinal center B cells in mice, is a member of the cytidine deaminase family. We herein report mutations in the human counterpart of AID in patients with the autosomal recessive form of hyper-IgM syndrome (HIGM2). Three major abnormalities characterize AID deficiency: (1) the(More)
Activation-induced cytidine deaminase (AID), a putative RNA-editing enzyme, is indispensable for somatic hypermutation (SHM), class switch recombination, and gene conversion of immunoglobulin genes, which indicates a common molecular mechanism for these phenomena. Here we show that ectopic expression of AID alone can induce hypermutation in an artificial(More)
Infection with Helicobacter pylori (H. pylori) is a risk factor for the development of gastric cancer. Here we show that infection of gastric epithelial cells with 'cag' pathogenicity island (cagPAI)-positive H. pylori induced aberrant expression of activation-induced cytidine deaminase (AID), a member of the cytidine-deaminase family that acts as a DNA-(More)
The switch of the immunoglobulin isotype from IgM to IgG, IgE or IgA is mediated by class switch recombination (CSR). CSR changes the immunoglobulin heavy chain constant region (CH) gene from Cmu to one of the other CH genes. Somatic hypermutation introduces massive numbers of point mutations in the immunoglobulin variable (V) region gene, giving rise to(More)
Activation-induced cytidine deaminase (AID) is required for the DNA cleavage step in immunoglobulin class switch recombination (CSR). AID is proposed to deaminate cytosine to generate uracil (U) in either mRNA or DNA. In the second instance, DNA cleavage depends on uracil DNA glycosylase (UNG) for removal of U. Using phosphorylated histone gamma-H2AX focus(More)
Genome stability is regulated by the balance between efficiencies of the repair machinery and genetic alterations such as mutations and chromosomal rearrangements. It has been postulated that deregulation of class switch recombination (CSR) and somatic hypermutation (SHM), which modify the immunoglobulin (Ig) genes in activated B cells, may be responsible(More)
Somatic hypermutation (SHM) and class switch recombination (CSR) cause distinct genetic alterations at different regions of immunoglobulin genes in B lymphocytes: point mutations in variable regions and large deletions in S regions, respectively. Yet both depend on activation-induced deaminase (AID), the function of which in the two reactions has been an(More)
One of the front lines of the immune defence is the gut mucosa, where immunoglobulin- (IgA) is continuously produced to react with commensal bacteria and dietary antigens. It is generally accepted that, after antigenic stimulation in the Peyer's patches, IgA+ lymphoblasts (B220+IgA+) migrate through the lymph and blood circulation, and eventually home to(More)
The immune system has adopted somatic DNA alterations to overcome the limitations of the genomic information. Activation induced cytidine deaminase (AID) is an essential enzyme to regulate class switch recombination (CSR), somatic hypermutation (SHM) and gene conversion (GC) of the immunoglobulin gene. AID is known to be required for DNA cleavage of S(More)