Your Gut & the Immune System

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http://www.pickthebrain.com/blog/your-gut-5-things-you-didnt-know/

Your Gut: 5 Things You Didn’t Know

Written by Anita Chaperon - 12 Comments

2. It Controls Your Immune System

Over 60% of your immune system is contained in your gut. Remember

those ads about topping up your ‘good bacteria’ – well they have the

right idea.

http://www.psychologytoday.com/blog/health-matters/201104/mood-gut-bacteria-and-the-immune-system

Mood, Gut Bacteria, and the Immune System

Does the gut, immune system and stress interact?

Published on April 6, 2011 by

J. Hedaya, M.D., D.F.A.P.A in

Health

Matters

Many people would be surprised that the immune system, the

gastro-intestinal tract and

stress

interact, but that is what the most recent of a number of studies shows.

In this study on mice,

(Brain, Behavior,

and Immunity Volume 25, Issue 3, March 2011, Pages 397-407)

researchers demonstrated that psychological stress causes almost

immediate changes to the gut bacterial population, and that some of these

affected sub-populations strongly influence the effect that stress has on

immunity. In the study, the researchers exposed mice to social

disruption, which is known to cause increases in circulating cytokines

('hormones of the immune system), which themselves induce enhanced

reactivity in the immune system. The researchers found that social

disruption altered bacterial counts of some gut bacteria sub-populations,

particularly when the bacteria were assessed immediately after stress

exposure. Stress exposure increased the relative abundance of bacteria in

the genus Clostridium, which often causes prolonged and severe diarrhea

(generally after antibiotc use). The stressor also increased circulating

levels of IL-6 which was significantly correlated with stressor-induced

changes to certain other sub-populations. In a second experiment, these

researchers found that a combination of antbiotics prevented the stress

induced increase IL-6. This means that certain gut bacteria are necessary

for stressor-induced increases in circulating cytokines.So, not only does

stress affect the gut bacterial population, but these organisms are also

required for activation of the immune system.

This information becomes even more relevant for

psychiatric

disorders such as

OCD, and

depression, as activation of IL-6 has clearly been associated with

depression. In fact blockers of IL-6 (eg etanercept) have been shown to

reduce depression scores. Furthermore, we can now see, that stress, via

its effect on gut bacteria, and hence the immune system (IL-6) can change

brain

function. We know this because IL-6 activates a certain enzyme (IDO),

which actually 'steals' or syphons-off tryptophan from its normal

metabolic pathway ( ie conversion into serotonin and then melatonin) and

instead converts it into chemicals that increase activity of glutamate

(in depression) at an excitatory-and some times toxic- receptor (NMDA) in

the brain. The result of all of this is increased depression, anxiety,

and reduced

memory. In

mice this effect can take moths to reverse. The upshot of all of this, is

that stress, the gut, the brain and the immune system are really

intimately linked, and inseparable. While this might be news to most

psychiatrists, it is not news when one understands the Whole Psychiatry

model.

http://www.medpagetoday.com/InfectiousDisease/GeneralInfectiousDisease/11343

Gut Bacteria Play Key Role in Immune System

Download Complimentary Source PDF

By , North American Correspondent, MedPage Today

Published: October 16, 2008

Reviewed by

Dori F.

Zaleznik, MD; Associate Clinical Professor of Medicine, Harvard

Medical School, Boston.

Dan Littman, M.D., Ph.D.

Professor of Molecular Immunology NYU School of Medicine

NEW YORK, Oct. 16 -- The development of key immune cells is triggered by

specific types of bacteria in the gut, a finding that could lead to new

therapies for diseases of inflammation, researchers here said.

In the absence of bacteria from the cytophaga-flavobacter-bacteroidetes

phylum -- or CFB, for short -- the immune cells are also not present, at

least in mice, according to Dan Littman, M.D., Ph.D., of New York

University, and colleagues.

On the other hand, when bacteria from that phylum are introduced into

animals lacking them, the result is a restoration of Th17 immune cells,

Dr. Littman and colleagues said in the Oct. 16 issue of Cell Host

& Microbe.

Th17 cells -- CD4-positive cells that have a potent pro-inflammatory

effect-- are normally in a balance with another population of

CD4-positive cells, dubbed Foxp3-positive cells, which play a regulatory

role in the immune system.

The finding that different populations of gut bacteria influence the

development of the Th17 cells could open the door to new treatments for

inflammatory bowel disease and other illnesses of the immune system, Dr.

Littman said.

" The number of inflammatory diseases known to involve T helper 17

cells seems to be growing every week, " Dr. Littman said. For that

reason, he and colleagues have been studying the development of the

cells.

In a series of experiments in mice, he and colleagues showed that a

complete absence of so-called commensal bacteria in the small intestine

leads to a lack of Th17 cells. Commensal bacteria are the useful

organisms that help in digestion and aid in protecting against pathogens.

In commercially available germ-free mice -- which have a complete lack of

bacteria and fungi -- Th17 cells were not detectable and the presence of

interleukin-17 secreted by the cells was at the limit of detectability.

On the other hand, Foxp3-positive cells were increased, even though the

total number of CD4-positive cells was two- to three-fold lower than

normal.

When the researchers used a cocktail of antibiotics to destroy the

commensal bacteria, they found that the proportion of Th17 cells fell by

half after four weeks of treatment. In mice given the cocktail from

birth, the proportion of Th17 cells was 80% lower than in control animals

by six to eight weeks of age.

Dr. Littman and colleagues then broke out individual antibiotics to see

if they influenced the number of Th17 cells. Vancomycin (Vancocin) --

which mainly attacks Gram-positive bacteria -- had a similar effect to

the whole cocktail.

On the other hand, antibiotics that attack anaerobic and Gram-negative

bacteria had little effect.

More than 90% of the commensal intestinal bacteria -- in both mice and

humans -- are either members of the Gram-negative CFB phylum or the

Gram-positive Firmicutes phylum, the researchers noted.

A series of experiments showed that members of the CFB phylum are not

present in animals that lack Th17 cells, Dr. Littman and colleagues said,

although those from the Firmicutes phylum remain.

The researchers found that some strains of experimental mice have

intestinal bacteria but no Th17 cells. Comparing those animals with other

strains, Dr. Littman and colleagues discovered that CFB bacteria were

associated with the creation of Th17 cells.

Exactly which members of the CFB phylum induce the cells is currently

under study, the researchers said.

" It's not the amount of microbial flora but the kind of microbial

flora that seems to count, " Dr. Littman said.

The findings point to ways of manipulating the immune system, commented

Yasmine Belkaid, Ph.D., of the National Institutes of Health, one of the

sponsors of the study.

" There is more and more evidence that gut flora have a tremendously

important influence on human health, " Dr. Belkaid said in a

statement. " This new study is the first report that has associated a

defined set of gut flora with the induction of specific immune

cells. "

The study was supported by the Medical Institute, the Helen

and Kimmel Center for Biology and Medicine, the Sandler Program

for Asthma Research, the National Gnotobiotic Rodent Resource Center, the

NIH, the Foundation, and the Canadian Institutes of Health

Research. The researchers did not report any conflicts.

GOOGLE on gut immune system for more info

Sheri Nakken, former R.N., MA, Hahnemannian

Homeopath

Vaccination Information & Choice Network, Washington State, USA

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