The Puzzle of the Human Appendix, Solved! - It defends the gut's
beneficial bacteria

Stefan Anitei, Science Editor

For long, the appendix has been regarded as a trouble causing
evolutionary ballast. But a new research suggests that the appendix
could have in fact an active beneficial role, being a "safe house" for
the good gut bacteria.

Based on observations and experiments, the team at the Duke University
Medical Center said that the beneficial bacteria located in the
appendix can determine a gut to repopulate with its flora, following a
bout of diarrhea that cleanses it completely.
"While there is no smoking gun, the abundance of circumstantial
evidence makes a strong case for the role of the appendix as a place
where the good bacteria can live safe and undisturbed until they are
needed," said lead researcher Dr. William Parker, assistant professor
of experimental surgery.

The appendix is a thin 2-4 in (5-10 cm) long pouch situated at the
joint of the large and small intestines. Its function has been a
puzzle for the researchers for long, and the only sure thing is that
it contains an immune system.

Some microbes from the gut digest food that the human digestive juices
cannot, providing some useful nutrients for the body (like vitamin K).
The Duke team points that the immune system cells encountered in the
appendix have a role of defending, rather than killing the beneficial
bacteria.

For ten years, Parker has been investigating the dynamics of the gut
bacteria in biofilms, thin layers located atop the intestines
consisting of a mix of microbes, mucous and immune system molecules.

"Our studies have indicated that the immune system protects and
nourishes the colonies of microbes living in the biofilm. By
protecting these good microbes, the harmful microbes have no place to
locate. We have also shown that biofilms are most pronounced in the
appendix and their prevalence decreases moving away from it." said
Parker.

"This new function of the appendix might be envisioned if conditions
in the absence of modern health care and sanitation are considered.
Diseases causing severe diarrhea are endemic in countries without
modern health and sanitation practices, which often results in the
entire contents of the bowels, including the biofilms, being flushed
from the body," he explained.

"The appendix's location and position is such that it is expected to
be relatively difficult for anything to enter it as the contents of
the bowels are emptied. Once the bowel contents have left the body,
the good bacteria hidden away in the appendix can emerge and
repopulate the lining of the intestine before more harmful bacteria
can take up residence. In industrialized societies with modern medical
care and sanitation practices, the maintenance of a reserve of
beneficial bacteria may not be necessary. This is consistent with the
observation that removing the appendix in modern societies has no
discernable negative effects." continued Parker.

For several decades, the "hygiene hypothesis" has been the explanation
for the high incidence of appendicitis in developed countries. The
obsession for "hygiene" in these countries could boost allergy and
even autoimmune disease because people's immune systems are not
challenged on a daily base by the array of parasites or germs common
in the environment and when the immune systems are triggered, they
often overreact.

"This overreactive immune system may lead to the inflammation
associated with appendicitis and could lead to the obstruction of the
intestines that causes acute appendicitis. Thus, our modern health
care and sanitation practices may account not only for the lack of a
need for an appendix in our society, but also for much of the problems
caused by the appendix in our society." said Parker.

TAGS: bacteria gut appendix

9th of October 2007, 11:14 GMT | Copyright (c) 2007 Softpedia |

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