Re: News: Rat study shows dirty better than clean.


John Wilkins wrote:
Ron O <rokimoto@xxxxxxx> wrote:

Harlequin wrote:
Ye Old One <usenet@xxxxxxxxx> wrote in
news:1ct89213dmjkmve091jit6hoce76ksjchn@xxxxxxx:

Rat study shows dirty better than clean

By SETH BORENSTEIN, AP Science Writer Fri Jun 16, 10:56 PM ET
http://news.yahoo.com/s/ap/20060617/ap_on_sc/dirty_rats_8

WASHINGTON - Gritty rats and mice living in sewers and farms seem to
have healthier immune systems than their squeaky clean cousins that
frolic in cushy antiseptic labs, two studies indicate. The lesson for
humans: Clean living may make us sick.

The studies give more weight to a 17-year-old theory that the
sanitized Western world may be partly to blame for soaring rates of
human allergy and asthma cases and some autoimmune diseases, such as
Type I diabetes and rheumatoid arthritis. The theory, called the
hygiene hypothesis, figures that people's immune systems aren't being
challenged by disease and dirt early in life, so the body's natural
defenses overreact to small irritants such as pollen.
[snip]

This idea has been around for a while.

If this hypothesis is true, maybe the solution is to find a safe
way to challenge the immune system in youth: some way besides
exposing children to things that are likely to kill them.

But all that being said: allergies are a small price to
pay for not dying as a child of some terrible infectious
disease (assuming the hypothesis is true). Likewise everything
else. I am quite sure that those about to die during a
cholera epidemic in previous centuries would have gladly
traded it in for having allergies and an increased risk of
developing stuff like diabetes and arthritis many years
down the line.

--
Anti-spam: replace "usenet" with "harlequin2"

Childhood vaccinations should challenge the immune system. Since this
obviously isn't enough you would have to institute more regular and
diverse challenges. They will have to do more research to determine if
they have to unnecessarily challenge children.


As I understand it, and I'm an immunologist the same way I'm a
paleontologist (i.e., not at all) vaccines don't "challenge" the immune
system, they *educate* it. That is, they present the surface molecules
that can have antigens formed against them in preparation for an
infection later on.

By "challenge" they mean stimulate. The immune response is pretty much
identical when you're injected with attenuated influenza virus, or
inhale the virions that make you sick as hell for a week. You're only
missing out on the "sick as hell" part. Attenuated (or killed) viruses
don't reproduce like the actual pathogens, so you might not get as many
plasma cells or cytotoxic T cells, but whenever you develop immunity to
something (and you don't develop immunity to all pathogens) you have
produced memory B & T cells in addition to the plasma cells (that make
antibodies) and cytotoxic T cells (that meander about and kill
pathogens). These memory cells remain quiescent (sometimes for years)
until you are once again exposed to that pathogen, or a reasonable
facsimile thereof.


I find this Nietzschean idea that we become stronger by overcoming
challenges, immunological or otherwise, absurd. What doesn't kill us can
leave us weak and susceptible to the next "challenge".

I don't think anyone seriously proposes that these minor pathogens are
making the immune system stronger in some way. They might be
distracting it. I have read (in Zimmer''s book, Parasite Rex) that
children in developing nations that have relatively high load of minor
parasites- i.e., ones that have almost evolved into commensals- are
still healthy, and have virtually no autoimmune disorders.

I believe an acquaintance of yours went through an experimental
treatment for a serious intestinal autoimmune disorder that made use of
this phenomenon, John.

Chris


--
John S. Wilkins, Postdoctoral Research Fellow, Biohumanities Project
University of Queensland - Blog: evolvethought.blogspot.com
"He used... sarcasm. He knew all the tricks, dramatic irony, metaphor,
bathos, puns, parody, litotes and... satire. He was vicious."

.

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