The ability to fine-tune antibodies against resident bacteria in the gut is necessary to maintain normal gut immune function according to a report published in Nature Immunology.
A certain type of antibody, called IgA, occurs abundantly in secretions of mucosal tissues such as the gut. The enzyme AID is responsible for directing diversification of antibody genes, a process known as somatic hypermutation (SHM), which is crucial to ensure that the gut is well protected against the various different pathogens that may attack.
Tasuku Honjo and colleagues found that mice unable to perform SHM, due to expression of a mutant AID protein, display aberrant bacterial overgrowth and excessive gut immune cell activation. These mutant mice likewise have skewed microbial populations in their gut and are less-well equipped to handle disease-causing bacteria in the intestine and are more sensitive to gut tissue damage evoked by cholera toxin.