g201 Barley

Allergens within Grass Pollens

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  • Latin name: Hordeum vulgare
  • Family: Poaceae (Gramineae)
  • Subfamily: Pooideae
  • Tribe: Triticeae
  • Common names: Barley, Common Barley, Barleycorn, Malt
  • Source material: Pollen
Barley pollen g201 should be differentiated from Barley the food, f6.
 
A grass species producing pollen, which often induces hayfever, asthma and conjunctivitis in sensitised individuals.

Allergen Exposure

Geographical distribution
Barley is probably native to the Middle East, from Afghanistan to northern India. It first came under cultivation 12,000 or more years ago. It is widely cultivated in temperate areas of the world for its edible seed. Because of its wide range of geographical distribution, Barley has accumulated a vast array of genetic variability.
 
Barley is the fourth most important cereal crop in the world after wheat, maize, and rice. Russia is the largest producer of Barley, followed by Great Britain, France, the United States, then Canada and other countries.
 
Barley is an erect annual grass. Its stout, simple stem is hollow and jointed and can grow more than a metre high. The narrow, tapering leaves ascend the stem in two ranks, with some overlapping; and their bases form loose sheaths around the stem. The flowers are hermaphrodite (have both male and female organs) and are pollinated by wind. The flowers grow in bristly-bearded terminal spikes, producing eventually the elliptic, furrowed Barley grains. The time of flowering depends on the cultivar, and cultivars include winter-hardy varieties. The period from planting to harvest varies from 60 days to 4 months.
 
Basically, Barley can be divided into three types: two-rowed, with kernels in two lines; four-rowed, with kernels in four lines; and six-rowed, with kernels in six lines. Barley may also be divided up into three types based on the nature of the hulls, varying from tight to loose to non-existent.
 
Environment
Barley is not known in the wild. It may be found as a relict of cultivation but does not persist.
 
Barley is a staple food in the developing world, and is used in industrialized countries for animal feed and for speciality food products. Malt is a nutritious sweetener in various foods. It is also grown for distilling malt liquors and spirits, and is one of the primary components of beer. About half of the total US production is used for malting. Barley has many folk medicinal uses.

Unexpected exposure
Barley straw is used as bedding and packing material, for making hats and for the manufacture of cellulose pulp. It is a source of fibres for making paper, and a biomass for fuel, and it can be shredded and used as mulch.
 
Allergens
Hor v 9 has been described as a barley pollen allergen (1)
Southern blots suggested that Hor v 9 allergens exist as multiple isoforms in Barley (2).

Potential Cross-Reactivity

This 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). 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)) (3-4).  
 
Sequence comparisons showed that the Hor v 9 cDNA clones were also homologous to Group 5 allergens of Timothy grass (Phleum pratense) pollen and canary grass (Phalaris aquatica) pollen, and the Group 9 allergen of ryegrass (Lolium perenne) pollen (2).
The Barley pollen cDNA, and three other cloned allergens: Phl p 5, Phl p 5a (from Timothy) and Lol p 1b (from Rye grass) were demonstrated to have extensive nucleotide and amino acid sequence similarity to Poa p 9 isoallergens of Meadow grass (5).

Clinical Experience

IgE mediated reactions
Barley pollen can induce asthma, allergic rhinitis and allergic conjunctivitis.
In a French study, Barley pollen and Rye pollen were demonstrated using specific IgE tests to be the cereals that were the most prevalent sensitising allergens in children with grass pollinosis (6).
 
Aerobiological surveys have detected Barley pollen in the atmosphere of Madrid, Spain (7).
 
Other reactions
Flour made from the seed of Barley may result in symptoms of food allergy, occupational allergy, or allergy reactions to beer(8-10).   
 
Compiled by Dr Harris Steinman, harris@zingsolutions.com

References:

    1. Astwood JD, Mohapatra SS, Ni H, Hill RD. Pollen allergen homologues in barley and other crop species. Clin Exp Allergy 1995;25(1):66-72 
    2. Astwood JD, Hill RD. Cloning and expression pattern of Hor v 9, the group 9 pollen isoallergen from barley. Gene 1996;182(1-2):53-62 
    3. Yman L. Botanical relations and immunological cross-reactions in pollen allergy. 2nd ed. Pharmacia Diagnostics AB. Uppsala. Sweden. 1982: ISBN 91-970475-09 
    4. Yman L. Pharmacia: Allergenic Plants. Systematics of common and rare allergens. Version 1.0. CD-ROM. Uppsala, Sweden: Pharmacia Diagnostics, 2000. 
    5. Astwood JD, Mohapatra SS, Ni H, Hill RD. Pollen allergen homologues in barley and other crop species. Clin Exp Allergy 1995;25(1):66-72 
    6. Lelong M, Thibaudon M, Thelliez PH. Is it necessary to test children having summer respiratory problems with cereal pollens? [French] Allerg Immunol (Paris) 1989;21(10):394-5 
    7. Subiza J, Masiello JM, Subiza JL, Jerez M, Hinojosa M, Subiza E. Prediction of annual variations in atmospheric concentrations of grass pollen. A method based on meteorological factors and grain crop estimates. Clin Exp Allergy 1992;22(5):540-6 
    8. Curioni A, Santucci B, Cristaudo A, Canistraci C, Pietravalle M, Simonato B, Giannattasio M. Hypersensitivity to beer is due to a 10-kDa protein derived from barley. Clin Exp Allergy 1999;29(3):407-13 
    9. Chiung YM, Shen HD, Huang JW. Immunoblot analysis of components of barley recognized by IgE antibodies in sera from pig farm workers. Electrophoresis 1998;19(8-9):1317-8 
    10. Vidal C, Gonzalez-Quintela A. Food-induced and occupational asthma due to barley flour. Ann Allergy Asthma Immunol 1995;75(2):121-4

2005



Further Reading