Nut Cracked? Desensitising yourself to allergies

Being allergic to any kind of food can be a real hassle. Having a nut allergy can be of particular annoyance because of all of those pesky “traces” that every other type of food you come across on the shelf seems to have.

Peanut allergy tops the list of offenders when it comes to severe and fatal allergic reactions to food and can really impact on the sufferer’s quality of life as they’re always trying to avoid any contaminated food as well as obviously trying to keep away from peanuts themselves! If proper measures aren’t taken, then they’re at real risk of anaphylaxis – the itchiness and swelling of the exposed area upon contact with the allergen, in this case: the peanut.

Not that Peanut!

Not that Peanut!

Oral Immunotherapy

A recent trial undertaken in Cambridge looked at the possibility of desensitising children’s allergic response to peanuts. This would mean that rather than the immune system seeing the peanut protein as a foreign agent, it would “get used” to it so that the body could build up tolerance over time.

The researchers did this by a process called oral immunotherapy (OIT), which means exactly what you think it does – modifying the immune system by administering something via the mouth, as opposed to injecting it for example.

The 99 children were split into two groups: half received the treatment and the other half were given a placebo. But because this was a crossover trial, the groups were switched after the first of two rounds of testing so that all participants received the treatment.

More, more, more!

Small amounts (2 mg to begin with – equivalent to one 70th of a peanut) of peanut protein in the form of powder, like a sort of flour, were mixed into the participants’ food. Over 26 weeks this amount was gradually increased every two to three weeks until it reached 800 mg, a level which was maintained until the end of the first round of testing.

They also underwent a double-blind placebo-controlled food challenge. This was to assess how the course of the individual’s allergy was progressing – i.e. how much of the allergen they could tolerate before allergic symptoms started to develop, and if it was actually peanuts that were causing the symptoms. This was obviously done under strict medical supervision just in case any severe reaction did take place.

The children were given peanut flour in increasing amounts

The children were given peanut flour in increasing amounts

By incrementally increasing the amount of peanut flour, the participants’ tolerance levels to peanuts saw a 25 fold increase compared to before testing.  After the first round of therapy, 62% of those who received OIT became desensitised, and up to 91% of the children who were originally allergic could continue to eat 800 mg of peanuts (around five whole peanuts) every day after six months.

Whilst this first study of its kind was a success, it has by no means given us an outright cure for food allergy. These sorts of experiments need to take place in hospitals for the most part, just in case something does go wrong. As with many clinical trials, it will be a long time until any clinically or commercially available option becomes viable.

One drawback of this study was that the team don’t know how long the results of desensitisation will last.

The Body’s Response

So what’s actually causing the body to give us an allergic reaction? After all, we don’t all react the same way to peanuts!

Well, peanut allergy is classified as a type one hypersensitivity reaction. This is when the body sees the food as foreign and harmful, and overreacts. This allergen is recognised by B cells which present the protein to T cells, particularly T Helper 2  cells. This process stimulates the production of antibodies, especially the IgE antibody, causing the immune response to kick in.

IgE then continues to bind to specialised cells in the blood like mast cells and basophils. With the antibody bound both to the mast cell and the protein, the mast cell begins to release chemicals such as histamine.

Histamine is known as a vasoactive mediator so it acts on the smooth muscle in the bronchi and causes blood vessels to dilate. This is often the beginning of an anaphylactic reaction.

The research group from Cambridge gained results that suggest that the mast cells and basophils in the blood were desensitised so that they could not trigger downstream events that lead to an allergic reaction.

So I hope this has been an enlightening read, especially if you are unfortunate enough to suffer from a peanut allergy. I hope you’ve learned a thing or two as well!

Alex

References

Anagnostou K, Islam S, King Y, Foley L, Pasea L, Bond S, Palmer C, Deighton J, Ewan P, & Clark A (2014). Assessing the efficacy of oral immunotherapy for the desensitisation of peanut allergy in children (STOP II): a phase 2 randomised controlled trial. Lancet PMID: 24485709

Images adapted from:

http://www.officialpsds.com/Delete–No-entry-sign-PSD39034.html

http://www.bubblews.com/news/1223632-jeff-dunham-and-peanut

http://outlawfarmer.wordpress.com/2011/05/17/senegalese-peanut-butter-tomato-sauce/

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