[img]2012q1/ct_etoefm_etoeflistz_0307_20121[/img] [br] What is the lecture mainl

M: One type of immune response has to do with bees- actually any insect of that class, including hornets and fire ants. If you’ve ever been stung or bitten, you know how painful it is. But stings and bites usually aren’t dangerous, unless you have lots of them at the same time, or unless you have an allergic reaction to the venom. A massive allergic reaction to a sting is known as anaphylaxis. The term anaphylaxis is Greek for "a lack of protection." But the name is sort of inaccurate. Anaphylaxis is actually a disease, a severe form of allergic, um, over-response by the immune system when it’s suddenly faced with a foreign substance. That foreign substance is the bee’s venom, or in some cases it’s certain foods, like nuts, eggs, and shellfish ... or drugs, especially antibiotics like penicillin. Anaphylaxis-or anaphylactic shock-is one of those true emergencies where minutes can make the difference between life and death. It can start within seconds, although sometimes it has a delay of thirty minutes or more.
W: Excuse me, Professor Watson, but how do you recognize it? I mean, there’s a difference between a few seconds and thirty minutes. So how do you ... like, how do you know when a person’s in anaphylactic shock?
M: Sometimes it’s hard to identify the real reason why someone is in trouble. Unfortunately, that’s what happened last year to a little girl who ate a peanut cookie at a birthday party. No one who was with her at the time knew she was allergic to peanuts, so they didn’t know why she suddenly went into respiratory distress. The reason, of course, was anaphylaxis. But by the time the medics got there, it was too late, and the girl died.
   So, how do we identify anaphylactic shock? The first sign is the victim becomes very weak and feels sick. There may be an itchy rash near the site of the sting, if it’s a bee sting, or a tingling in the mouth, if it’s a food allergy. The tissues of the face and throat may swell up. The chest feels tight, and the person has trouble breathing-this is when every minute, every second matters. The blood pressure drops dangerously low. Finally, the person may lose consciousness and stop breathing. When this happens, the person’s life is in danger. Anaphylactic shock, as you can see, can be life threatening in some cases.
   What happens to the immune system? First, it has to be exposed previously to the offending substance-the bee venom, the peanuts, or whatever. People don’t get anaphylaxis from their first bee sting. The immune cells that produce antibodies ... they ... uh ... they have to be sensitized to the offending substance at least once before they overreact to it the second or third time. We don’t understand why some unlucky immune systems go crazy the next time the}’ encounter the same substance. But some immune systems do sort of go crazy. The cells pour out far more antibody than they need. This sets off a whole series of reactions involving the release of histamine into the bloodstream. Histamine makes the blood vessels dilate and get "leaky," and the liquid part of the blood leaks out into the tissues. This is what causes the skin rash, the potentially fatal swelling, the narrowing of the airways, and the drop in blood pressure. The worst part is all of this happens within minutes.
W: Because this can happen so fast-I mean, going into shock-how do we prevent-I mean, is there a way we can stop somebody from dying of this?
M: With anaphylaxis, a few minutes can make the difference between life and death, so the keys to survival are being prepared and acting quickly. The most important tool to have is called an epi-pen- basically an automatic syringe that lets you self-administer the drug epinephrine into your body, a drug that helps combat the effects of anaphylaxis.