Segmented filamentous bacteria or Candidatus Savagella are members of the gut microbiota of rodents, fish and chickens, and have been shown to potently induce immune responses in mice.

In mice, these bacteria grow primarily in the terminal ileum in close proximity to the intestinal epithelium where they are thought to help induce T helper 17 cell responses.

[4] Intriguingly, Segmented Filamentous Bacteria were found to expand in AID-deficient mice, which lack the ability to mount an appropriate humoral immune response because of impaired somatic hypermutation; parabiotic experiments revealed the importance of IgA in eliminating Segmented Filamentous Bacteria.

[5] This goes hand in hand with an earlier study demonstrating the ability of monocolonization with Segmented Filamentous Bacteria to dramatically increase mucosal IgA levels.

[6] Segmented Filamentous Bacteria are species specific, and may be important to immune development.