Cause Of Harmful Allergies Identified

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Main Category: Allergy
Also Included In: Blood / Hematology;  Immune System / Vaccines;  Clinical Trials / Drug Trials
Article Date: 03 Jan 2008 - 15:00 PDT

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There is a chemical in the blood, which if controlled, may prevent harmful allergic reactions - anaphylaxis - to such foods as peanuts, medicines and insect venom, according to an article published in the New England Journal of Medicine (NEJM). A new study indicates it may have found out which chemical this is, and why levels of it are not controlled adequately in some people.

Approximately 1,000 Americans die each year as a result of anaphylaxis. About 30,000 people in the USA each year have an anaphylactic reaction, out of an estimated 12 million who suffer from some kind of food allergy. This study is the first to show there is a link between anaphylaxis and a chemical in the blood.

In this study the scientists wanted to monitor levels of PAF (platelet-activating factor) in 64 participants - 41 had suffered at least one episode of anaphylaxis (anaphylaxis participants), while the other 23 had not (healthy participants). PAF is a chemical released by cells. Animals with high PAF levels in their blood have been associated with anaphylaxis in previous studies. The researchers wanted to find out whether PAF levels in humans might also be linked to allergy. They also measured participants' PAF acetylhydrolase. PAF acetylhydrolase is an enzyme which breaks PAF down as soon as it is released into the body. In other words, PAF acetylhydrolase controls the levels of PAF.

The patients who had suffered an anaphylaxis incident were divided into groups, depending on the severity of their reactions.

The researchers report that 4% of their healthy participants (control group) had raised PAF levels, compared to 20% of the anaphylaxis participants who had experienced minor symptoms, and 100% of those who had experienced severe reactions.

The participants who had experienced the worst anaphylaxis reactions also had the lowest levels of PAF acetylhydrolase - in other words, they had the lowest levels of the enzyme which breaks PAF down, they were the least able to control PAF levels. The article reports that in a separate study, it was found that nine children who had died as a result of anaphylaxis to peanuts also had significantly low levels of the enzyme.

The researchers believe that this study may eventually lead the way to developing methods of predicting who are most at risk of experiencing mild to severe anaphylaxis, and also creating some kind of treatment, such as enzyme replacement therapy.

They also stressed that further studies on this are needed. There may well be other chemicals released by the body that play a role in anaphylaxis.

"Platelet-Activating Factor, PAF Acetylhydrolase, and Severe Anaphylaxis"
Peter Vadas, M.D., Ph.D., Milton Gold, M.D., Boris Perelman, Ph.D., Gary M. Liss, M.D., Gideon Lack, M.D., Thomas Blyth, M.D., F. Estelle R. Simons, M.D., Keith J. Simons, Ph.D., Dan Cass, M.D., and Jupiter Yeung, Ph.D.
NEJM Volume 358:28-35 January 3, 2008 Number 1
Click here to view abstract online

Written by - Christian Nordqvist
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