Crossreactions involving plant allergens.

Abstract

The allergen sources from plants may be classified as pollinic and nonpollinic. The more important sources are the pollens from grasses, weeds, and trees, which are all responsible for the greatest part of seasonal clinical allergic manifestations such as hay fever and birch and ragweed pollinoses. The nonpollinic plant allergen sources are mainly represented by foods such as fruits, vegetables, and spices, but there are also air-borne allergens such as the allergenic dust from Ficus benjamina, Hevea brasiliensis, or soja hulls. In this respect, allergies to plants are chiefly respiratory, but food and occupational allergies to plants also exist. In its broadest definition, crossreactions correspond to allergic symptoms provoked in a patient by various offending agents containing common allergenic structures at the molecular (allergen molecules) or submolecular (epitope) levels. It should be borne in mind that a crossreaction may be limited to the presence of crossreacting IgE antibodies in the serum without any clinical translation (1). The reason for such a dissociation will be discussed later in this review. Crossreacitivity of grass-sensitized patients toward a large number of related grass species has been recognized for a long time. This has produced practical applications both in diagnosis (i.e., through skin testing and detection of grass-specific IgE antibodies), and in the therapeutic management of these patients. On the other hand, crossreactivity against apparently botanically unrelated or distantly related allergenic plants is a well-established but more puzzling phenomenon. In these