New Defense Against Snake Bites Identified

Snakebite! When it's a copperhead or a rattler, that means venom. Conventional wisdom says that a body's immune system can make the bite worse when it raises immune defenses, sometimes throwing victims into shock. But a new study suggests that one kind of defensive cell, the mast cell, actually does fight off venom.

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DON GONYEA, host:

Snake venom is nasty stuff. A single bite from a king cobra injects enough to kill a dozen people. But scientists have now discovered something in the body that seems to disarm the venom. It's an unlikely bunch of cells from the immune system with a bad reputation for causing the ill effects of asthma and allergies.

NPR's Christopher Joyce has more.

CHRISTOPHER JOYCE reporting:

When he was a young boy, Steven Galley(ph) brought home a snake. He remembers his mother screamed. Now Galley is Chief of Pathology at Stanford University's Medical School. He still likes snakes, but studies asthma and allergies and mast cells in the immune system.

Dr. STEVEN GALLEY (Chief of Pathology, Stanford Medical School): In medical school, one learns that mast cells are bad actors. They contribute to disease, such as asthma, or to these very dramatic immune responses called anaphylaxis, and also to hay fever and runny eyes in the allergy season. And it's true that they do have these effects.

JOYCE: Mast cells overreact sometimes to allergens that invade the body. It's assumed they'd do the same when someone gets envenomated, as the experts like to say. In fact, mast cells can cause more damage than the bite itself.

Now, here's where Galley's affection for snakes comes in. A colleague of his at Stanford, also a snake fan, stumbled on a weird fact. Mast cells sometimes attack a compound in the human body that chemically looks just like the venom of the Israeli mole viper. So the two scientists did some experiments to see if maybe mast cells might neutralize snake venom.

They got special mice that had no mast cells and some that did. The ones with mast cells resisted a dose of snake venom much better than the ones without mast cells, sometimes ten times better. And it worked for venom from the Western diamondback rattlesnake, from copperheads, and also honeybees.

So Galley suggests in the current issue of the journal Science that maybe mast cells do serve some useful purpose.

Dr. GALLEY: There have been some studies which indicate that for some types of bacterial infection and some types of parasite infection, mast cells helped protect the host. Perhaps snakebite is another example, or honeybee stings, and there may be others yet to be discovered.

JOYCE: Galley is now testing human mast cells against snake venom and hopes they may lead to new treatments for snakebite. In the meantime, don't jump to any rash conclusions about mast cells in your body.

Dr. GALLEY: Did I mention that people should not assume that because mast cells offer some protection it's okay to be bitten by a snake?

JOYCE: That's true. But I don't think people are going to be running out, you know, fondling rattlesnakes.

Dr. GALLEY: Yeah. One would hope that they would not do that.

JOYCE: Exactly.

Christopher Joyce, NPR News.

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