Structural features of allergenic molecules.

In this paper the relation between protein allergenicity (the capacity to induce IgE antibody production or the capacity to activate mast cells sensitized with IgE antibodies induced by a cross-reactive allergen) and protein structure is discussed. While cross-reactivity is to a large degree predictable from primary sequence comparisons, the IgE-inducing capacity is mostly determined by factors other than the primary sequence. Two routes to IgE are discussed: (1) the atopic route (used by allergens from pollen and mites) in which a direct switch from mu to epsilon is common and (2) the 'modified Th2' route (used by allergens from pets) in which the class switch to IgE is often preceded by a switch to IgG4. According to this working hypothesis, the choice between these two routes is determined at the level of the germinal center activity.