Characteristics and Immunobiology of Grass Pollen Allergens

Abstract

Grass pollens are one of the most important airborne allergen sources worldwide. About 20 species from five subfamilies are considered to be the most frequent causes of grass pollen allergy, and the allergenic relationships among them closely follow their phylogenetic relationships. The allergic immune response to pollen of several grass species has been studied extensively over more than three decades. Eleven groups of allergens have been identified and described, in most cases from more than one species. The allergens range from 6 to 60 kD in apparent molecular weight and display a variety of physicochemical properties and structures. The most complete set of allergens has so far been isolated and cloned from Phleum pratense (timothy grass) pollen. Based on the prevalence of IgE antibody recognition among grass pollen-sensitized individuals, several allergens qualify as major, but members of two groups, groups 1 and 5, have been shown to dominate the immune response to grass pollen extract. Isoform variation has been detected in members of several of the allergen groups, which in some cases can be linked to observed genetic differences. N-linked glycosylation occurs in members of at least three groups. Carbohydrate- reactive IgE antibodies have been attributed to grass pollen sensitization and found to cross-react with glycan structures from other allergen sources, particularly vegetable foods. Another cause of extensive cross-reactivity are the group 12 allergens (profilins), which belong to a family of proteins highly conserved throughout the plant kingdom and present in all tissues. Members of eight allergen groups have been cloned and expressed as recombinant proteins capable of specific IgE binding. This development now allows diagnostic dissection of the immune response to grass pollen with potential benefits for specific immunotherapy.

Previously undescribed grass pollen antigens are the major inducers of T helper 2 cytokine-producing T cells in allergic individuals

“…Despite the importance of Th2 cells and their associated cytokines in the pathogenesis of allergic respiratory disease, studies of antigens considered as triggers of T-cell responses have so far been mostly limited to those known to bind IgE antibodies (7,8) and induce IgE-mediated immediate hypersensitivity reactions (9). However, several clues suggest that T-cell and IgE reactivity might not exclusively be linked to each other.…”

Pollen Loads and Allergic Rhinitis in Darwin, Australia: A Potential Health Outcome of the Grass-Fire Cycle

“…The majority of allergenic grass species characterized thus far belong to the Pooideae sub-family which has the C3 photosynthetic pathway, yet on a global scale, about one-half of all known grass species belong to a tropical functional group with the C4 photosynthetic pathway (Gaut, 2002). Significantly, many allergens from four C4 species that have been characterized to date have been shown to be distinct from those in the Pooideae sub-family (Andersson and Lidholm, 2003). These include important allergic species Sorghum halepense (Johnson grass) and Cynodon dactylon (Bermuda grass) that are now present on most continents.…”

Proteome analysis of maize pollen for allergy-relevant components

“…Grass pollen contains about 1000 different components, but only some are IgE reactive and can cause allergic reactions. Pollen allergens are classified according to their biochemical structure and immunological reactivity, leading to the identification of ten different allergen groups [4]. Table 1 presents an overview of timothy grass pollen allergens and their immunological and biochemical characteristics.…”