Cultivated wheat

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Code: g15
Latin name: Triticum sativum
Source material: Pollen
Family: Poaceae (Gramineae)
Sub family: Pooideae
Tribe: Triticeae
Common names: Wheat, Bread Wheat, Common Wheat.

Synonyms: T. vulgare, Triticum sativum

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.

Pollen

A grass species producing pollen, which often induces hay fever, 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 south-western Australia.

Cultivated Wheat is an annual grass. The root is fibrous. The stem is simple, round, smooth, erect, hollow or pithy, and up to 1.5m tall. The leaves are flat, narrow, veined, roughish above, 20 to 38cm long, and about 1.3cm broad. The flowers are borne on a 4-cornered terminal spike, 5 to 7.5cm 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 is also a base for alcoholic beverages. Bran from the flour milling is 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.

Allergen Description

The following allergens have been characterised:

Tri a 1, an expansin, a Group 1 grass allergen (1, 2).

Tri a 2, a Group 2 grass allergen (1, 3).

Tri a 3, a protein of unknown function (4, 5).

Tri a 4, a pectate lyase (berberine bridge enzyme), a Group 4 grass allergen (1, 6).

Tri a 5, a Group 5 grass allergen (1).

Tri a 7, a calcium-binding protein (7, 8).

Tri a 12, a profilin, found both in pollen and in Wheat kernel (1, 9).

Tri a 13, a polygalacturonase (10).

Cultivated Wheat pollen contains a 1,3-beta-glucanase allergen (11).

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 grass g12, Barley g201, and Couch grass (Agropyron repens) as well as Lymegrass (Elymus arenarius). Extensive cross-reactivity among the different individual species of the genus may 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)) (12, 13).

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.

The presence of group 1, 2, 4 and 5 grass allergens, a profilin, a polygalacturonase and calcium binding protein may result in variable cross-reactivity with pollen from other grasses, weeds and trees, depending on the similarity of these panallergens with those found in this pollen. However, these cross-reactions have not been fully elucidated yet.

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 characterised 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 (1).

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 (11).

Clinical Experience

IgE-mediated reactions

Anecdotal evidence suggests that Cultivated Wheat pollen may induce symptoms of asthma, allergic rhinitis and allergic conjunctivitis in sensitised individuals; however, few studies have been reported to date (14).

A study on pollen sensitisation in an area of Spain, where cereal crops are very important, found that grass pollen was the main source of clinical symptoms in 32.30% of 19 718 asthmatics. Wheat and cereal crop pollen showed a very low prevalence of sensitisation. Patients with Wheat flour allergy after ingestion, and/or with baker’s asthma, were not sensitised to Wheat pollen, despite it containing some common allergens (15).

A review by the Portuguese hospital of Cova da Beira of 335 female and 130 male asthmatic patients with asthma reported that 70% had allergic asthma, and 30% had non-allergic asthma. The major allergen sensitisers, as evaluated by skin-prick testing and specific IgE, were grasses (Lolium perenne, Phleum pratense, Dactylis glomerata and Poa pratensis), cereals (Secale cereale, Triticum sativum and Avena sativa), house dust mites, and pollen from trees (Olea europea and Platanus acerifolia), the weed Parietaria judaica and the mould Alternaria alternate (16). In an earlier study in Portugal evaluating sensitisation to pollens in 32 children under 8 years of age attending an allergy unit, 72% presented with symptoms of allergic rhinitis, 66% with conjunctivitis, 50% with asthma and 34% with both allergic rhinitis and asthma. All children were skin-prick sensitised to grass pollen, and 38% of them were monosensitised. The grass pollen sensitization for frequency order was Dactylis (94%), Hordeum (75%), Phleum (72%), Poa (69%), Avena (66%), Festuca (63%), Triticum (59%), Secale (53%), Lolium (50%) and Zea (31%) (17).

A study investigating patterns of sensitisation to common inhalant allergens, especially pollens, in Turkish children living in the Trakya region, reported positive skin reactions occurring in 420 (77.9%) of the children. Of these, 277 (51.4%) were sensitised to pollen, of which 173 were positive to cereal pollen (32.1%). The most common positive skin test among the pollens was to cultivated wheat (Titicum vulgare) (n = 116, 21,5%), followed by rye grass (Lolium perenne) and orchard grass (Dactylis glomerata) (18).

An analysis of the positive skin tests of 614 respiratory allergic patients in Turkey found that the important allergens were house dust, Dermatophogoides pteronyssinus, cockroach, mosquito and Dermatophogoides farinea, Johnson grass, Cultivated wheat, Rye, Orchard, and Maize pollen (14). [words missing somewhere, perhaps after “cockroach, mosquito and”?]

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 (19).

Compiled by Dr Harris Steinman, developer of Allergy Advisor, http://allergyadvisor.com

 

Original: 02/05/2002

Updated: 30/03/2010

References

  1. 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.
  2. Jin Y, Tashpulatov AS, Katholnigg H, Heberle-Bors E, Touraev A. Isolation and characterisation of two wheat beta-expansin genes expressed during male gametophyte development. Protoplasma 2006;228(1-3):13-9.
  3. Rihs HP, Rozynek P, May-Taube K, Welticke B, Baur X. Polymerase chain reaction based cDNA cloning of wheat profilin: a potential plant allergen. Int Arch Allergy Immunol 1994;105(2):190-4.
  4. Balzer HJ, Borisiuk L, Meyer HM, Matzk F, Bäumlein H. A pollen allergen-encoding gene is expressed in wheat ovaries. Plant Mol Biol 1996;32(3):435-45.
  5. Korzun V, Balzer HJ, Balzer A, Baumlein H, Borner A. Chromosomal location of three wheat sequences with homology to pollen allergen encoding, DNA replication regulating, and DNA (cytosine-5)-methyltransferase genes in wheat and rye. Genome 1996;39(6):1213-5.
  6. Nandy A, Petersen A, Wald M, Suck R, Kahlert H, Weber B, Becker WM, Cromwell O, Fiebig H. Primary structure, recombinant expression, and molecular characterization of Phl p 4, a major allergen of timothy grass (Phleum pratense). Biochem Biophys Res Commun 2005;337(2):563-70.
  7. Wopfner N, Dissertori O, Ferreira F, Lackner P. Calcium-binding proteins and their role in allergic diseases. Immunol Allergy Clin North Am 2007;27(1):29-44.
  8. Smith PM, Xu H, Swoboda I, Singh MB. Identification of a Ca2+ binding protein as a new Bermuda grass pollen allergen Cyn d 7: IgE cross-reactivity with oilseed rape pollen allergen Bra r 1. Int Arch Allergy Immunol 1997;114(3):265-71.
  9. International Union of Immunological Societies Allergen Nomenclature: IUIS official list http://www.allergen.org/ 2009.
  10. Grote M, Swoboda I, Valenta R, Reichelt R. Group 13 allergens as environmental and immunological markers for grass pollen allergy: studies by immunogold field emission scanning and transmission electron microscopy. Int Arch Allergy Immunol 2005;136(4):303-310.
  11. 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.
  12. Yman L. Botanical relations and immunological cross-reactions in pollen allergy. 2nd ed. Pharmacia Diagnostics AB. Uppsala, Sweden. 1982: ISBN 91-970475-09.
  13. Yman L. Pharmacia: Allergenic Plants. Systematics of common and rare allergens. Version 1.0. CD-ROM. Uppsala, Sweden: Pharmacia Diagnostics, 2000.
  14. 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.
  15. Armentia A, az-Perales A, Castrodeza J, Duenas-Laita A, Palacin A, Fernandez S. Why can patients with baker's asthma tolerate wheat flour ingestion? Is wheat pollen allergy relevant? Allergol Immunopathol (Madr) 2009;37(4):203-4.
  16. Lourenco O, Fonseca AM, Taborda-Barata L. Demographic, laboratory and clinical characterisation of adult portuguese asthmatic patients. Allergol Immunopathol (Madr) 2007;35(5):177-83.
  17. Diamantino C, Caeiro E, Martins L, Almeida F, Lopes ML. Pollen sensitisation in children less than 8 years old. Rev Port Imunoalergol 2006;14(3):245-9.
  18. Yazicioglu M, Oner N, Celtik C, Okutan O, Pala O. Sensitization to common allergens, especially pollens, among children with respiratory allergy in the Trakya region of Turkey. Asian Pac J Allergy Immunol 2004;22(4):183-90.
  19. 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.

As in all diagnostic testing, the diagnosis is made by the physican based on both test results and the patient history.