Allergies are more common than ever and are generating more and more, often major, health problems. Knowledge about the molecular mechanisms that lead to disorders in the interplay of the immune system and the environment is a prerequisite for developing new therapies for the causal treatment of allergies.
The term allergy refers to hypersensitivity disorders of the immune system that react to normally harmless environmental substances. Common allergic reactions range from weak, local irritations to acute, life-threatening anaphylactic shock and chronic, life-long inflammation and organ function disorders.
Allergies are not only a medical problem as well as the subject of intensive research. They are also of huge social and economic importance, in particular for highly developed industrial nations, but also to a growing extent for other countries. It is estimated that around 300 million people worldwide suffer from asthma and around 180,000 people die every year from the consequences of this disease. According to the Federal Health Monitoring Information System (GBE), a person’s life expectancy is reduced by around one per cent due to allergies and their effects. These figures resemble those associated with diabetes mellitus. The burden of allergies on the national economy is enormous due to the high direct costs of drugs and treatment as well as the indirect costs arising from the loss of working days (short-term sick leave or permanent invalidity).
The "Allergy Research in Germany" atlas published by the German Society for Allergology and Clinical Immunology (DGAKI) in 2008 summarises the latest data on allergic diseases and their consequences for the German economy. The majority of costs, i.e. around 60 per cent, arise from bronchial asthma, followed by allergic skin inflammations. The costs of treatment of allergic skin inflammations are generated equally from allergic contact dermatitis and atopic eczema (better known as neurodermatitis, a name that is slightly misleading as it relates to neuropathies). With regard to healthcare costs, allergic rhinitis, or hay fever, is the third most frequent allergic disease in Germany. Allergic rhinitis is mainly caused by pollen as well as by the house dust mite Dermatophagoides pteronyssimus, which is invisible to the naked eye.
The number of people suffering from allergies has dramatically increased in Europe and North America over the last decades. A health survey carried out in Germany found that around 40 to 43 per cent of all Germans have developed an allergy at one time during their lives. In the 1990s, the number of hay fever sufferers increased by 70 per cent. The increase of bronchial asthma incidences in children is particularly alarming; the health survey found that the incidence of asthma in first-year school children increases every year by 0.6 per cent. Nowadays, around 18 per cent of all children and adolescents suffer from allergies. In addition to the aforementioned diseases, food allergies, which considerably impair a person's quality of life, have grown dramatically in number.
The majority of researchers believe that the (excessively) high hygiene standards in industrialised countries is the major cause of the steep increase in the incidence of allergic diseases. According to this “hygiene hypothesis”, the balanced maturation of the immune system required to differentiate between harmful and harmless antigens happens at the time of birth and during the first years of life. In order to effectively maturate, the growing infant needs to come into contact with a large number of microbial stimuli present in the natural environment of humans. However, the urban lifestyle in the western world is making it more and more difficult to come into contact with microbes and other harmful substances. A recently published epidemiological report has shown that genetic factors also play a role in people’s susceptibility to developing allergies. Intolerances to common, normally harmless food constituents such as wheat and cow’s milk proteins evolve during early childhood when the development of the immune system is closely linked with the development of the digestive system as it comes into contact with foreign antigens. Food allergies usually develop later in a person’s life; they might be the entry point of a general allergy career that could later lead to asthma and other respiratory tract diseases.
People suffering from genetic atopic syndrome characterised by the overproduction of IgE antibodies, are thought to develop allergies more easily than other people. Atopic hypersensitivity reactions include asthma and allergic rhinitis, as well as systemic anaphylaxy. These reactions are referred to as type I reactions; they occur as a result of the allergen-induced, IgE-mediated activation of mast cells in the mucous lining. Type II and III allergic reactions are mediated by IgG antibodies (complement system, phagocytes) and include incompatibility reactions to certain drugs (penicillin) and serum disease. Type IV reactions, to which contact dermatitis also belongs, are mediated by T-cells and lead to the activation of macrophages and cytotoxic T-cells. So-called TOLL-like receptors play a major role in the development of type IV allergic responses.
In all cases, allergies are the result of highly complex immune reactions involving numerous signalling chains whose interactions have recently been clarified in greater detail. As the articles of the dossier on allergic diseases show, scientists working at Baden-Württemberg universities are making a considerable contribution to improving our understanding and potential treatment of allergies.Growing knowledge of the molecular mechanisms underlying allergic diseases raises hopes that it may be possible to develop causal allergy treatments. Up until now, medical treatment focused on the alleviation of symptoms rather than on the curative treatment of the allergies. Exact knowledge of the molecular structure of allergens is an excellent starting point for developing therapies against life-threatening allergies. A group of Australian researchers has developed an effective and harmless allergy vaccine. Another group of researchers has developed a promising approach for the treatment of skin allergies, which involves the targeted stimulation of immune cells by probiotics based on bacteria and parasites. It is envisaged that the probiotic adaptation of the intestinal flora might promote the immunological balance in the digestive tract, thereby alleviating or even curing food allergies. EJ – 24.02.2011© BIOPRO Baden-Württemberg GmbH