RESUMO
Food allergy is an adverse food reaction as a result of immune mechanisms. In a sensitized individual, food allergens activate mast cells and basophils by binding with IgE present on the cell surface, resulting in the release of chemical mediators and various cytokines to cause various clinical symptoms of food allergy. Sensitization to food allergens can occur in the gastrointestinal tract (class 1 food allergy) or as a consequence of cross reactivity to structurally homologous inhalant allergens (class 2 food allergy). The class 1 food allergens are water-soluble glycoproteins with 10-70 kD size that are resistant to heat, acid and enzymes. On the other hand, the class 2 food allergens are highly unstable and degraded by heat or enzymatic digestion. Much progress has been made in identifying and isolating food allergen. Recently cDNAs for many proteins have been isolated and recombinant proteins have been generated. These techniques make it easier to characterize each responsible food allergens. Plant food allergens are classified into families and superfamilies by their structural and functional properties. The most of plant food allergens are the cupin and prolamin superfamilies and the protein families of the plant defense system. The cupin superfamily includes allergenic seed storage proteins of 7s globulin (vicilin) and 11s globulin (legumin). 2s albumin seed storage proteins, the nonspecific lipid transfer proteins, and the cereal alpha-amylase and protease inhibitors belong to the prolamin superfamily. Profilins, heveins, and nonspecific lipid transfer proteins are present in a variety of pollens, nuts, seeds, fruits, and vegetables. These are considered as panallergens, causing a significant degree of IgE-mediated cross-reactivity. Detailed informations about the character of food allergens can be used to develop more sophisticated diagnostic methods and treatment modalities in the near future. Further knowledge of food allergens is also useful to assess the allergenicity of novel protein of genetically mo.