Northern Colorado Asthma and Allergy Clinic

Complement-ary peanuts: Peanuts can contribute to anaphylactic shock by activating complement

Marat Khodoun, PhD, Richard Strait, MD, Tatyana Orekov, MS, Simon Hogan, PhD, Hajime Karasuyama, PhD, De’Broski R. Herbert, PhD, Jörg Köhl, MD, and Fred D. Finkelman, MD

Peanut allergy is among the most serious and lethal of food allergies, and recent studies show increasing frequency, mostly among children. Attempts to manage peanut allergy by strict avoidance are not always effective and can have grave consequences. Compared to other food allergens, there seems to be something different about peanuts.

In a study in the February 2009 issue of The Journal of Allergy and Clinical Immunology, Khodoun, et al. looked to see what it is about peanuts that make them such a unique threat. They investigated whether certain peanut molecules might also cause peanut-induced shock through a different mechanism of the immune system.

The authors found that shock could be caused by injecting mice with a peanut extract, even though the mice had never been immunized to peanuts. The authors additionally discovered that peanut extract caused shock by turning on the mouse complement system. The complement system is a series of chemicals that react to help clear harmful stuff from our body and is a component of the larger immune system that is not adjustable and does not change over the course of a person's lifetime, as inmunity can with allergies.

The authors suggest that the high frequency, persistence and severity of peanut allergy might result from a combination of properties that make it the perfect allergen: poorly digestible proteins that are easily detected by our immune system; the ability of at least one of these proteins to turn on allergic sensitization; and the ability of peanut molecules to rapidly activate complement and make large amounts of C3a, the anaphylatoxin capable of causing a shock-like syndrome similar to that of an allergic reaction. Anaphylatoxins can trigger release of the contents of mast cells and basophils, such as histamine, which produce a local inflammatory response. If the release is too strong, it can cause shock.

The researchers also observed that tree nuts produce a similar effect, while skim milk and egg white do not. They conclude that peanut may be particularly allergenic because of its unique molecular properties. The peanut continues to reveal itself.

2009-04-13