Summary

Bromus inermis is a perennial cool-season grass species that produces pollen that is considered to contribute to hay fever symptoms in central and western North America. However, no further details are available as case reports specifically associating B. inermis pollen with allergic symptoms have not been published to date. Three allergenic molecules have been characterized from brome grass pollen, including a Group 1 expansin (Bro i 1), a Group 5 ribonuclease (Bro i 5), and a calcium-binding protein (Bro i 7). Pooideae grasses have marked homology of major allergen groups 1, 2/3, 4, and 5, and a degree of cross-reactivity between B. inermis and other Pooideae species can be expected.

Route Of Exposure

Main

Inhalation of pollen produced by B. inermis can elicit allergic symptoms in sensitized individuals.

Clinical Relevance

Pollen from brome grasses including B. inermis is considered to contribute to hay fever symptoms in central and western North America, however, no further details are available as case reports specifically associating B. inermis pollen with allergic symptoms have not been published to date.

Cross-Reactivity

An early study demonstrated significant cross-allergenicity and similar radioallergosorbent test (RAST) inhibition patterns between northern grasses (Timothy grass, June grass, rye grass, red top, and meadow fescue) and brome grass, western wheat, and quack grasses. However, another study found no antigenic cross-reactivity between pollen from Bermuda grass (Cynodon dactylon), which is classed as a southern grass, and B. inermis.

Pooideae grasses have marked homology of major allergen groups 1, 2/3, 4, and 5, and smooth brome is a member of the Poeae tribe which also includes Kentucky bluegrass, fescue, and orchard grasses. As such, and despite a lack of published studies specifically assessing cross-reactivity of the three B. inermis allergens, a degree of cross-reactivity between B. inermis and other Pooideae species can be expected.