False oat-grass

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Code: g204
Latin name: Arrhenatherum elatius
Source material: Pollen
Family: Poaceae (Gramineae)
Sub family: Pooideae
Tribe: Aveneae
Common names: False Oat grass, Tall Oatgrass, Onion Couch

There are two subspecies or varieties: one has swollen bases in the main shoots, resembling small onion bulbs, and is sometimes called 'Onion Couch'; the other lacks these swellings.

Pollen

A grass species producing pollen, which often induces hay fever, asthma and conjunctivitis in sensitised individuals.

Allergen Exposure

Geographical distribution

False Oat grass is native to Europe, and was brought to the United States early in the last century. It is now grown widely, for making hay and for grazing, in the central and northern states. World distribution includes the USSR, East Asia, and Africa.

False Oat grass is a hardy, upright, perennial bunchgrass growing up to 180cm high, with many leaves scattered along the stems. The seed head resembles that of Oats: hence the name. The leaf blades, rolled in the bud shoot, are flat, linear, up to 50cm long and 10mm wide, and sometimes sparsely hairy.

The inflorescence is a panicle, green to purple, shining, erect or nodding, oblong or ovate, contracted, and up to 35mm wide and 60cm long. The hermaphrodite (containing both male and female organs) florets number one to three per spikelet. Incomplete (male) florets also occur at the base of the inflorescence. False Oat grass flowers from November in the Southern Hemisphere and from May in the Northern Hemisphere.

Environment

Often found in dry meadows or pastures, but very seldom in the wild.

Allergen Description

The following allergens have been characterised:

Arr e 1, a Group 1 Grass allergen (1, 2).

Arr e 5, a ribonuclease, a Group 5 Grass allergen (3).

Potential Cross-reactivity

Extensive cross-reactivity among the different individual species of the genus may be expected, as well as to a certain degree among members of the family Poaceae, particularly in the tribe Aveneae (Sweet Vernal grass (g1), Cultivated Oat (g14), Velvet grass (g13), Canary grass (g71)) (4, 5).

Early studies of the antigens in Meadow grass (Kentucky bluegrass) pollen, compared with False oat grass and the combined extracts of Timothy, Orchard (cocksfoot), Velvet and Rye grasses, indicated that these grasses contain many cross-reactive antigens (6). Similarly, immunological partial identity between isolated major allergens of Timothy pollen and the corresponding pollen allergens of False oat, Orchard and Rye grass were demonstrated (7).

The presence of group 1 and 5 grass allergens may result in variable degrees of cross-reactivity with pollen from other grasses, weeds and trees, depending on the similarity of these panallergens with those found in this pollen (1, 6-8). However, these cross-reactions have not been fully elucidated yet (9).

For example, extensive IgE cross-reactivity has been observed between the allergens of the Pooideae grasses as a result of the presence of a group 1 grass allergen (8).

Clinical Experience

IgE-mediated reactions

Anecdotal evidence suggests that False Oat grass pollen may induce symptoms of asthma, allergic rhinitis and allergic conjunctivitis in sensitised individuals (3); however, no studies have been reported to date.

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

References

  1. Matthiesen F, Løwenstein H. Group V allergens in grass pollens. II. Investigation of group V allergens in pollens from 10 grasses. Clin Exp Allergy 1991;21(3):309-20.
  2. Standring R, Spackman V, Porter SJ. Distribution of a major allergen of rye grass (Lolium perenne) pollen between other grass species. Int Arch Allergy Appl Immunol. 1987;83(1):96-103.
  3. Hejl C, Wurtzen PA, Kleine-Tebbe J, Johansen N, Broge L, Ipsen H. Phleum pratense alone is sufficient for allergen-specific immunotherapy against allergy to Pooideae grass pollens. Clin Exp Allergy 2009;39(5):752-9.
  4. Yman L. Botanical relations and immunological cross-reactions in pollen allergy. 2nd ed. Pharmacia Diagnostics AB. Uppsala, Sweden. 1982: ISBN 91-970475-09.
  5. Yman L. Pharmacia: Allergenic Plants. Systematics of common and rare allergens. Version 1.0. CD-ROM. Uppsala, Sweden: Pharmacia Diagnostics, 2000.
  6. Chakrabarty S, Løwenstein H, Ekramoddoullah AK, Kisil FT, Sehon AH. Detection of cross-reactive allergens in Kentucky bluegrass pollen and six other grasses by crossed radioimmunoelectrophoresis. Int Arch Allergy Appl Immunol 1981;66(2):142-57.
  7. Løwenstein H. Immunological partial identity and in vitro inhibitory effect of two major timothy pollen allergens to whole pollen extract of four grasses. Int Arch Allergy Appl Immunol 1978;57(4):379-83.
  8. Van Ree R, Van Leeuwen WA, Aalberse RC. How far can we simplify in vitro diagnostics for grass pollen allergy?: A study with 17 whole pollen extracts and purified natural and recombinant major allergens. J Allergy Clin Immunol 1998;102(2):184-90.
  9. Johansen N, Weber RW, Ipsen H, Barber D, Broge L, Hejl C. Extensive IgE cross-reactivity towards the Pooideae grasses substantiated for a large number of grass-pollen-sensitized subjects. Int Arch Allergy Immunol 2009;150(4):325-34.

 

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