g11 Brome grass

Allergens within Grass Pollens

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  • Latin name: Bromus inermis
  • Family: Poaceae (Gramineae)
  • Subfamily: Pooideae
  • Tribe: Bromeae
  • Common names: Brome grass, Bromegrass, Smooth Brome, Rescue grass
  • Source material: Pollen
Not to be confused with Bromus arvensis - Field Brome, a cool-season bunchgrass introduced from Europe in the late 1920's into the USA and used as cover crop and for green manure in parts of northeastern and north-central regions.
 
Other common species of the genus include:
  • B. arvensis
  • B. mollis
  • B. racemosis.
A grass species producing pollen, which may induce hayfever, asthma and conjunctivitis in sensitised individuals.

Allergen Exposure

Geographical distribution
Brome grass is native to Europe, China and Siberia. It was introduced into North America in the 1880's, where it has since been cultivated in the northern regions from Alaska and all the Canadian provinces and territories south to southern California and New Mexico, northern Oklahoma, and North Carolina. It extends from Northern Europe eastwards to China. It is also widely distributed in Argentina and elsewhere in South America.
 
Brome is a cool-season, sod-forming grass which resists trampling, making it excellent for grazing and soil conservation. It grows up to 1.2 m tall. It is the only grass with a sealed sheath. Usually in the middle of the leaf blade there is an impression of the letter "V" or "W", vertical on the leaf. The numerous blades, both basal and from the stem, are flat but rolled in the bud-shoot, 4 to 13 mm wide, 15 to 55 cm long, flat, tapering to a sharp point, and with scabrous margins.
 
The inflorescence is an open panicle from 6 to 17 cm long bearing 6- to 11-flowered spikelets that are pale green to slightly purple-tinged. In the Northern Hemisphere, Brome grass starts flowering in May and finishes in September. The seeds ripen from August to September. The flowers are hermaphrodite (have both male and female organs) and are pollinated by wind. Brome grass reproduces by seed, rhizomes, and tillers, but spread by seed is weak.
 
Two principle types of Brome are recognized, the northern and southern. The northern type is weakly rhizomatous, with leaves well up on the stem and short glumes. A few northern cultivars are actually bunchgrasses. The southern type is strongly rhizomatous, with leaves near the base of the stem and long glumes. Other notable differences are earlier spring growth of the southern type and more even growth of the northern type through the growing season.
 
Environment
Brome grass is found in riparian zones, valley bottoms, and a variety of dryland sites.
 
Allergens
No allergens from this plant have yet been characterised.

Potential Cross-Reactivity

An extensive cross-reactivity among the different individual species of the genus could be expected, as well as to a lesser degree among members of the subfamily Pooideae (1-2).  
 
In an early study, Brome grass, Western Wheat, and Quack grasses demonstrated RAST inhibition patterns similar to the northern grasses (Timothy, Meadow grass, Rye, Redtop, Meadow Fescue, and Sweet Vernal grass) (3). 
 
Inhibition studies of IgE antibody binding to Dac g 4 (Dactylis glomerata - Cocksfoot grass) with other pollen extracts confirmed the presence of cross-reactive allergens in Secale cereale (Cultivated Rye), Lolium perenne (Rye grass), Festuca elatior (Meadow Fescue), Holcus lanatus (Velvet grass), Bromus arvensis (Field Brome), Poa pratense (Meadow grass), Hordeum sativum (Barley), and Phleum pratense (Timothy grass) (4). Considering the presence of Group 4 allergens in Field Brome, the probability of a similar Group 4 allergen being present in Brome grass is high. Group 4 grass pollen allergens are glycoproteins with a molecular weight of 50 to 60 kD, which are present in many grass species.
 
Almost 75% of patients allergic to grass pollen display IgE reactivity to Group 4 allergens, which hence can be regarded as major grass pollen allergens (5). Further, Phl p 4 homologes with similar molecular weights were detected in Dactylis glomerata (Orchard grass), Festuca pratensis (Meadow Fescue), Holcus lanatus (Velvet grass), Poa pratensis (Meadow grass), and Lolium perenne (Rye grass). Group 4 homologes are present in the various grass extracts, but to different extents (6).

Clinical Experience

IgE mediated reactions
Brome grass pollen can induce asthma, allergic rhinitis and allergic conjunctivitis.
 
Brome grass pollen has been recorded as an aeroallergen in the Western Cape, South Africa (7).
 
Compiled by Dr Harris Steinman, harris@zingsolutions.com

References:

    1. Yman L. Botanical relations and immunological cross-reactions in pollen allergy. 2nd ed. Pharmacia Diagnostics AB. Uppsala. Sweden. 1982: ISBN 91-970475-09 
    2. Yman L. Pharmacia: Allergenic Plants. Systematics of common and rare allergens. Version 1.0. CD-ROM. Uppsala, Sweden: Pharmacia Diagnostics, 2000. 
    3. Martin BG, Mansfield LE, Nelson HS. Cross-allergenicity among the grasses. Ann Allergy  1985;54(2):99-104 
    4. Leduc-Brodard V, Inacio F, Jaquinod M, Forest E, David B, Peltre G. Characterization of Dac g 4, a major basic allergen from Dactylis glomerata pollen. J Allergy Clin Immunol 1996;98(6 Pt 1):1065-72 
    5. Fischer S, Grote M, Fahlbusch B, Muller WD, Kraft D, Valenta R. Characterization of Phl p 4, a major timothy grass (Phleum pratense) pollen allergen. J Allergy Clin Immunol 1996;98(1):189-98 
    6. Fahlbusch B, Muller WD, Rudeschko O, Jager L, Cromwell O, Fiebig H. Detection and quantification of group 4 allergens in grass pollen extracts using monoclonal antibodies. Clin Exp Allergy 1998 Jul;28(7):799-807
    7. Potter PC, Berman D, Toerien A, Malherbe D, Weinberg EG. Clinical significance of aero-allergen identification in the western Cape. S Afr Med J 1991;79(2):80-4

2002



Further Reading