g15 Cultivated wheat
Allergens within Grass Pollens
- Latin name: Triticum sativum
- Family: Poaceae (Gramineae)
- Subfamily: Pooideae
- Tribe: Triticeae
- Common names: Wheat, Bread Wheat, Common Wheat
- Source material: Pollen
Synonyms: T. vulgare, T. aestivum
In various countries, several species of Triticum are cultivated, among which is Triticum sativum (Triticum vulgare), the species most generally raised in the US and Europe. It has two varieties, Triticum aestivum, or Spring Wheat, and Triticum hybernum, or Winter Wheat.
A grass species producing pollen, which often induces hayfever, asthma and conjunctivitis in sensitised individuals.
Allergen Exposure
Geographical distribution
Cultivated Wheat is of uncertain origin, perhaps coming from the Middle East. It is known only under cultivation. This cereal is widely cultivated in temperate countries and in cooler parts of tropical countries. Next to Rice, it is the world's most widely used grain. Wheat covers about 50% of the total area sown with grain crops in Europe. Important areas of cultivation include Argentina, Belgium, Britain, Canada, China, India, Japan, Peru, Spain, Turkey, the US, southern USSR and southwestern Australia.
Cultivated Wheat is an annual grass. The root is fibrous. The stem is simple, round, smooth, erect, hollow or pithy, and up to 1.5 m tall. The leaves are flat, narrow, veined, roughish above, 20 to 38 cm long, and about 1.3 cm broad. The flowers are borne on a 4-cornered terminal spike, 5 to 7.5 cm in length, with a tough rachis. The spikelets are broad-ovate, 2- to 5-flowered, slightly overlapping, and pressed close to the rachis. The grains are loose.
Cultivated winter Wheat flowers from June to July (in the Northern Hemisphere), and Spring Wheat flowers in late summer. The flowers are hermaphrodite (have both male and female organs) and are pollinated by wind.
Environment
Wheat is grown in cultivated beds, usually as a crop but sometimes for pasturage. It is not known in the wild.
The seed can be cooked as a whole grain but it is more usually ground into a powder and used as a flour for making bread, fermented foods, pasta, cakes, biscuits, etc. The grain also is the source of alcoholic beverages. Bran from the flour milling is also an important livestock feed; the germ is a valuable addition to feed concentrate. Some Wheat is cut for hay.
Wheat is used as a shampoo and is a folk remedy.
Unexpected exposure
The straw has many uses: e.g., as a biomass, for fuel, thatching, mulch. mats, carpets, baskets, packing material, cattle bedding, and paper manufacturing.
Allergens
Cultivated Wheat pollen contains a 1,3-beta-glucanase allergen (1).
No other allergens from this pollen have yet been characterised, although many have been characterised from the seed.
Potential Cross-Reactivity
The pantemperate tribe Triticeae is notable for its cereal genera: Wheat, Barley and Rye. The close relation speaks in favour of cross-reactivity between Wild Rye grass g70, Cultivated Wheat g15, Cultivated Rye g12, Barley g201, and Couch grass (Agropyron repens) as well as Lymegrass (Elymus arenarius). An extensive cross-reactivity among the different individual species of the genus could be expected. There should be cross-reactivity with other members of the family Poaceae, particularly in the subfamily Pooideae (Rye grass (g5), Canary grass (g71), Meadow grass (g8), Timothy (g6), Cocksfoot (g3), Meadow Fescue (g4), Velvet (g13), Redtop (g9), Meadow Foxtail (g16), Wild Rye grass (g70)) (2-3).
Many varieties of Wheat are cultivated, such as Durum and Polish Wheat. All are closely related, and therefore have a high cross-reactivity to each other. Triticum and species of Secale have a tendency to hybridise, making it difficult to identify the genera.
Natural pollen extracts from Anthoxanthum odoratum (Sweet Vernal grass), Avena sativa (Cultivated Oat), Cynodon dactylon (Bermuda grass), Lolium perenne (Rye grass), Phragmites australis (Common Reed), Poa pratensis (Meadow grass), Secale cereale (Cultivated Rye grass), Triticum sativum (Cultivated Wheat), and Zea mays (Maize/Corn) were characterized regarding their allergen contents by means of specific antibodies and by IgE immunoblot inhibition with recombinant allergens from Phl p 1, Phl p 2, Phl p 5, and Bet v 2 using sera 193 European, American, and Asian subjects. Immunologically detectable Group 5 and Group 2 allergens were found in all these species except for C. dactylon and Z. mays (4).
Ole e 9, the major Olive tree pollen, is a 1,3-beta-glucanase, a member of the "pathogenesis-related" protein family. Ole e 9 is involved in the allergic responses of 65% of patients sensitised to Olive pollen. It has a 39% sequence identity with the 1,3-beta-glucanase from Wheat (1).
Clinical Experience
IgE mediated reactions
Cultivated Wheat pollen is a predominant cause of asthma, allergic rhinitis and allergic conjunctivitis (5).
Other reactions
A male athlete suffered complete respiratory arrest following a run through a Wheat field, which had caused Wheat pollen to be released. He had multiple wheals on both legs and complained of severe breathlessness before collapsing. It is possible that the symptoms were triggered either by the running itself, inhalation of allergens other than Wheat pollen, skin abrasions caused by contact with Wheat stalks, or a combination of these factors (6).
References:
- Huecas S, Villalba M, Rodriguez R. Ole e 9, a major olive pollen allergen is a 1,3-beta-glucanase. Isolation, characterization, amino acid sequence, and tissue specificity. J Biol Chem 2001;276(30):27959-66
- Yman L. Botanical relations and immunological cross-reactions in pollen allergy. 2nd ed. Pharmacia Diagnostics AB. Uppsala. Sweden. 1982: ISBN 91-970475-09
- Yman L. Pharmacia: Allergenic Plants. Systematics of common and rare allergens. Version 1.0. CD-ROM. Uppsala, Sweden: Pharmacia Diagnostics, 2000.
- Niederberger V, Laffer S, Froschl R, Kraft D, Rumpold H, Kapiotis S, Valenta R, Spitzauer S. IgE antibodies to recombinant pollen allergens (Phl p 1, Phl p 2, Phl p 5, and Bet v 2) account for a high percentage of grass pollen-specific IgE. J Allergy Clin Immunol 1998;101(2 Pt 1):258-64
- Guneser S, Atici A, Cengizler I, Alparslan N. Inhalant allergens: as a cause of respiratory allergy in east Mediterranean area, Turkey. Allergol Immunopathol (Madr) 1996;24(3):116-9
- Swaine IL, Riding WD. Respiratory arrest in a male athlete after running through a wheat field. Int J Sports Med 2001;22(4):268-9
2002