What makes an Allergen an Allergen?

The IgE-mediated immune response to allergens affect approximately 25% of the population of industrialized nations. They are characterized by elevated levels of serum IgE and a Th2-biased immune response to proteins that are often abundant and harmless to most individuals. These proteins are referred to as allergens. Interestingly, only a small fraction of the proteins in plants and animals are classified as allergens. Certain characteristics have been attributed to allergens, such as abundance in a food or the environment, resistance to heat and digestion, IgE induction and Th2 skewing. Similarities in sequential and structural features of allergens have been shown to exist and shown to contribute to cross-reactivity among different foods and inhalants. However, despite the sequential or structural similarities among various protein families that contain allergens, most of the proteins within that family are not considered allergens. So, while many of the features of allergens have been described, it is still difficult to predict the potential allergenicity of novel proteins or to definitively describe what makes an allergen an allergen. This Research Topic will focus on defining, describing or predicting, by empirical or via computational means, protein allergens and what characteristics contribute to making them allergens.  The scope of the research topics of interest includes: 1) allergen molecule characteristics, such as structure, function, sequence, stability, digestibility, posttranslational modification, cross-reactivity and food processing, in the case of food allergens; 2) the immune systems recognition and response to allergens such as antibody and cell surface receptor binding, including the role of antibody epitopes, the biochemical and biophysical properties of the antigens influencing their uptake, processing, activation, and presentation by (APCs), and the drive towards TH2 immunity, which are important in understanding allergic inflammation and allergens.