Allergen anaphylaxis

Anaphylaxis most commonly starts with symptoms on the skin or the respiratory tract (table 2). The symptomatology is variable there is no obligatory involvement of all organ systems. A major characteristic of anaphylaxis is the rather rapid onset of symptoms after contact with the elicitor. The interval varies between a few seconds or minutes until 1 or 2 h, partly dependent upon the route of application (rapid onset after intravenous allergen exposure) and degree of sensitization. Experience in insect sting anaphylaxis in... 

Fig.1. Food allergens are the most frequent causes of anaphylaxis in children. Data from the anaphylaxis registry of German-speaking countries (ANA-Net), n = 70. 

The most frequent elicitators of food allergy in children are peanuts and tree nuts [ 17]. In France the prevalence of food allergy has been estimated to be 3.2% [18]. Furthermore, in this study, food was identified as the most common cause of anaphylaxis. Here the major identified food allergens besides peanuts and tree nuts were shellfish, wheat and lupine flour [18]. 

Our understanding of anaphylaxis has advanced substantially since the original description of this phenomenon in the scientific literature over 100 years ago. There is now little reasonable doubt that the IgE-dependent activation of mast cells and basophils is the key event underlying most examples of allergen-induced anaphylaxis in humans [3-5]. IgE binds to the high-affinity IgE receptor, FcsRI, expressed on the... 

It is generally accepted (based on clinical and in vitro studies) that mast cells (and basophils), IgE and FceRI are involved in most cases of allergen-induced anaphylaxis in humans. However, it is difficult to define the exact roles and relative importance of mast cells, basophils, and other potential effector cells (e.g monocytes/macrophages, dendritic cells) in either IgE-dependent or IgE-independent human anaphylaxis. Unlike in mice, we neither have access to mast cell- or basophil-deficient humans nor can we genetically manipulate human subjects to produce such phenotypes. 

The route of antigen administration can alter the speed of antigen access to the circulation and, thus, the systemic symptoms in anaphylaxis models. For example, allergen ingestion typically induces anaphylaxis that includes gastrointestinal symptoms, such as diarrhea [4]. These intestinal anaphylaxis models in mice are dependent on IgE-induced mast cell activation, and the release of PAF and serotonin (rather than histamine) [1,4]. 

Fig. 2. IgG-mediated systemic versus local anaphylaxis, a IgG-mediated systemic anaphylaxis. When allergen-IgG immune complexes are formed in the circulation, basophils immediately capture them through IgG receptors on their surface and are activated to release PAF, that in turn act on vascular endothelial cells, leading to increased vascular permeability, b Passive cutaneous anaphylaxis. When allergen-IgG immune complexes are formed in the skin, they stimulate tissue-resident mast cells to release chemical mediators such as histamine, leading to local inflammation. 

The application and development of new in vitro diagnostic techniques aims to enable physicians to reach an allergy diagnosis with no risk for the patient. This is particularly desirable in the case of serious reactions such as anaphylaxis, by confirming the existence of an anaphylactic reaction and differentiating between individuals which present with sensitization but no cUnical symptoms following exposure to the allergen from those that show a serious clinical reaction. 

Over the last decade, new perspectives have been opened up with the use of natural purified and/or recombinant allergens for the molecular diagnosis of allergy which will provide us with precise information for the diagnosis of cUnical reactions experienced by patients and which are particularly applicable to the diagnosis of anaphylaxis. 

Diagnostic Tools for the Identification of Anaphylaxis-Triggering Allergens... 

Ebo DG, Ahrazem O, Lopez-Torrejon G, Bridts CH, Salcedo G, Stevens WJ Anaphylaxis from mandarin (Citrus reticulata) identification of responsible allergens. Int Arch Allergy Appl Immunol 2007 144 39-43. Raap U, Schaefer T, Kapp A, Wedi B Exotic food allergy anaphylactic reaction to lychee. J Invest Allergol Clin Immunol 2007 17 199-201. 

While in anaphylaxis caused by other frequent elicitors like food and drugs, allergen-specific immunotherapy is not established, immimotherapy with Hymenoptera venoms has been shown to be effective in three prospective controlled trials (table 4) [38-40] and also in a number of studies where patients were submitted to a sting challenge with the responsible insect during venom immimotherapy (table 5) [44]. While over 90% of vespid venom-allergic patients are fully protected and do not develop any... 

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