Panallergens and their impact on the allergic patient

So far, from more than 200,000 known plant species, about 50 are registered in the official allergen list of the International Union of Immunological Societies (IUIS) Allergen Nomenclature Subcommittee http://www.allergen.org webcite as capable of inducing pollen allergy in susceptible individuals [1]. Pollinosis-associated plants are characterized by production of high amounts of mostly anemophilous pollen and can be grouped as (i) trees (Fagales, Pinales, Rosales, Arecales, Scrophulariales, Junglandales, Salicales, and Myrtales), (ii) grasses (Bambusioideae, Arundinoideae, Chloridoideae, Panicoideae, and Poideae), and (iii) weeds (Asteraceae and Chenopodiaceae, and Urticaceae). The flowering seasons of allergenic plants spans the whole year, starting from early spring (trees), going over summer (grasses) and to late autumn (weeds). Allergenic pollen is a complex mixture of several molecules including major and minor allergens. Major allergens represent components to which the majority of patients (by definition >50%) reacting to a given allergen source is sensitized, whereas minor allergens are recognized by a limited number of patients. In many cases major allergens serve as marker allergens for sensitization to certain kinds of plants, e.g. Bet v 1 for birch, Cry j 1 and Cry j 2 for Coniferales allergies, Ole e 1 for Oleaceae [1], etc.The number of allergic individuals that appears to be mono-sensitized to a single allergenic plant is very limited. In fact, the majority of patients seems to display adverse reactions upon contact to multiple allergen sources. According to the botanical classification, this might be simply attributed to poly-sensitization to different allergenic plants [2]. Another explanation for this phenomenon is the concept of IgE cross-reactivity in which IgE antibodies originally raised against a given allergen can bind homologous molecules originating from a different allergen source. For example, homologous molecules of the birch pollen ma