The production of immunoglobulins E (IgE), i.e. the antibodies responsible for allergic reactions, is generally considered as noxious and as the result of a dysfunction in the immune system. A study led by Thomas Marichal, a postdoctoral researcher in the laboratory of Professor Steve Galli at Stanford University, showed that these antibodies can have a protective effect against the toxicity of honeybee and snake venoms.
It could therefore be possible that allergic immunity to different venoms and toxins has been maintained over the course of evolution as a major defence mechanism of the host. It might therefore be conceivable that, for a proportion of the population, an initial exposure to the venom and associated IgE may have a beneficial effect against the same venom upon subsequent exposure. Now, scientists would like to identify which factors determine whether the IgE antibodies are more likely to induce a noxious or a protective response.

In developed countries, almost one out of three people suffer from an allergic disorder. And this rate could well increase to one out of two people in coming years according to World Health Organisation (WHO) estimations. In fact, the WHO ranks allergies fourth in the list of chronic global diseases. The exact causes of increases in the number of allergies haven’t been identified, although different reasons have been suggested to explain this development. On the one hand, the growing vigilance of health professionals has generated increased screening in the past few years. On the other hand, our food and our environment have changed. As regards to food, there is a correlation between easier access to exotic products and the increase in food allergies. Furthermore, industrial products can contain “hidden” allergens or more allergenic products as a result of the manufacturing process. As regards to babies, certain allergies can develop as a result of food diversification introduced too early into their diet.

In terms of the environment, two main guilty parties have been pinpointed as a source of the growing number of allergies: pollution and the increasing aseptic environment in which people live. 

A dysfunction preserved over the course of evolution

An allergic reaction is considered as a dysfunction of the immune system. It is an exaggerated and unwanted reaction of the latter to foreign substances in the body, the majority of which are inoffensive. “In some people, contact with a particular allergen (for instance pollen, dust mite faeces, or peanut extracts) triggers a type 2 or Th2 response, i.e. a response involving immune cells capable of orchestrating the allergic reactions”, explains Thomas Marichal, researcher at the University of Liège, and currently performing a postdoctoral training at Stanford University in California (USA) as a Marie Curie IOF fellow from the European Commission. “Th2 lymphocytes produce cytokines that promote the synthesis of immunoglobulin E antibodies, underlying the allergic reaction. This Th2 response can be induced by many different allergens but the antibodies that are produced are specific to the allergen that triggered this response”, specifies Thomas Marichal. When they are produced, immunoglobulin E (IgE) antibodies circulate in the blood and the majority of them will bind to the surface of mast cells.