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[jpalter@sunweb.web.net (Jay Palter)]

From: twebster@bu.edu (Tom Webster)
Subject: big dioxin biology news
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Status: RO

Dear friends,
   BIG news on dioxin biology (and it couldn't be better timed with the
review meeting next Monday).  According to Science News, May 6, p.277,
someone has built a genetic "knock-out" for the Ah receptor in mice, meaning
that the receptor is non-functional from conception on.  We've been
expecting this experiment for quite some time.  I was beginning to wonder if
it was a lethal mutation!  The mice do make it through embryogenisis, but
many die shortly after birth.  Those that survive have decreased numbers of
immune system cells (T and B cells).  The numbers of these cells recovers,
but then crashes at puberty!  Furthermore, the mice livers show signs of
possible toxic harm (fibrosis), possibly due to lack of ability to
metabolize certain nasty things.
    This indicates that the Ah receptor and its presumed "natural ligand" do
something pretty interesting, although we're not sure what, but it appears
to have something to do with the immune system (as well as metabolism of
foreign compounds).
    More when I see the actual paper, due out in Science in this weeks
issue, May 5.  Best, Tom.

  
Tom Webster                  Boston University School of Public Health
tel: (617)638-4641           Department of Environmental Health, Talbot 3C
fax: (617)638-4857           80 East Concord St., Boston, MA 02118-2394, USA