Dioxin Posting

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


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