Immune system responses NOT predictable???

[Guest guest]

I think this is an incredibly important article relating to vaccine

use. What if administering a vaccine to elicit Th1 cells results in

production of Th17 instead--the immune cells which increase

inflammation and autoimmune responses??? Note the last paragaraph...

 

http://www.newscientist.com/article/mg20126934.500-can-we-reprogram-

the-immune-system.html

 

Can we reprogram the immune system?

28 January 2009 by Linda Geddes

Magazine issue 2693. Subscribe and get 4 free issues.

THE immune system may be far more flexible than we thought. The cells

that coordinate the activities of the immune system appear to change

their identity in response to environmental cues. This discovery

might one day make it possible to reprogram the immune system to

prevent autoimmune diseases and stop the body rejecting a transplant.

 

For years immune cells called T-helper (Th) cells were assumed to

come in just two types - Th1 cells, which help evict viruses and

bacteria from their host cells, and Th2 cells, primed to fight

parasites and bacteria in blood and other body fluids as well as

taking on allergens. Then things got complicated with the discovery

of two new classes of Th cells: regulatory T-cells (T-regs), which

dampen the immune system, and Th17 cells, involved in triggering

inflammation and autoimmunity.

 

But when John O'Shea, Bill Paul and Keji Zhao of the National

Institutes of Health in Bethesda, Maryland, and colleagues studied

all four types of T-helper cells from mice, they found hints that

these cells could switch roles or phenotypes in response to

environmental cues.

 

To test this, they exposed mouse T-regs to signalling molecules

associated with a Th1 response and found that the T-regs did indeed

behave like Th1 cells (Immunity, DOI:

10.1016/j.immuni.2008.12.009). " They turned out to be more flexible

than was envisioned, " says O'Shea.

 

In another study, Casey Weaver and colleagues at the University of

Alabama in Birmingham showed that TH17 cells can also morph into Th1-

like cells if they are deprived of a signalling molecule called TGF-

beta (Immunity, DOI: 10.1016/j.immuni.2008.11.005).

 

If T-helper cells are just as flexible inside our bodies, it could

affect how diseases are treated. For instance, the right molecules

would turn off harmful immune responses, such as those that cause

autoimmune diseases like rheumatoid arthritis. " If we understood the

rules for changing the phenotypes of these cells in humans, that

might be very helpful, " says O'Shea.

 

The right molecules could turn off harmful immune responses, such as

those that cause arthritis

However, there may be serious implications for immunotherapy trials

in which T-regs are injected into people with autoimmune disease to

dampen their immune response. At Northwick Park Hospital in London in

March 2006, six men were left fighting for their lives after

injections with a drug designed to activate T-regs.

 

Preliminary evidence from a study in mice suggests that T-regs might

turn into Th17-like cells under certain conditions, which would

actually exacerbate the illness by ramping up the autoimmune

response. " It is at least reason for pause and consideration, " says

O'Shea.

 

The new discoveries make it imperative for doctors to keep a close

eye on patients undergoing such immunotherapy, in case the immune

cells swap identities and cause the immune system to work in

unexpected, even harmful ways.

 

If TH1 cells are equally flexible, vaccines may not work as they are

intended, says Christopher Wilson of the University of Washington in

Seattle. For instance, if a vaccine against a virus triggers a TH1

response but the TH1 cells then change their identity for some

reason, " the pathogen might yet subvert the protection induced by the

vaccine " , he says.

 

 

From issue 2693 of New Scientist magazine, page 10.