Molecular Mimicry, the Hygiene Hypothesis, Stealth Infections and Other Examples of Disconnect between
Medical Research and the Practice of Clinical Medicine in Autoimmune Disease
http://drdavidbrady.com/media/drbrady/M ... 202013.pdf
Researchers have now gone beyond establishing mere
associations between the presence of various microbes
and autoimmune disorders. Some have actually experi-
mentally induced autoimmune disease by infecting ani-
mals with specific pathogens. Mazmanian et al. inocu-
lated a wild-type mouse with the bacterium Helicobacter
hepaticus to create an experimental mouse version of the
autoimmune disorder inflammatory bowel disease (IBD)
[10]. H. hepaticus activates Th17 cells which release
cytokines associated with inflammation, such as IL-17,
which cause symptoms of the disease. They then intro-
duced Bacteroides fragilis expressing the polysaccharide
A (PSA) to the gut of the animals where the PSA mole-
cule was taken up by dentritic cells and presented on
their surface, activating CD4 T cells and regulatory T
cells (Tregs). The Tregs release IL-10 which suppresses
the inflammatory action of IL-17, alleviating the IBD in
mice. In summary, the researches induced autoimmune
disease by introducing specific bacteria to the gut, and
resolved it by introducing another, making a compelling
argument for a causal relationship between the GI micro-
biota and autoimmune activity.