Meadow grass (Kentucky blue)
Summary
Kentucky bluegrass is a perennial grass growing in cold, humid temperate regions around the world. It has dark green leaves along with boat-shaped tips. It belongs to Poaceae family and Pooidaea subfamily.
This grass is wind pollinated and releases allergenic pollen grains massively during its peak flowering season. It is also known to be the most predominant seasonal aeroallergens that result in allergic symptoms such as allergic rhinoconjunctivitis (ARC) and asthma. The following allergenic components Poa p 1, Poa p 2, Poa p 5 including Poa p 5(a), Poa p 5(b), and Poa p 10 are found. Meadow grass contains major allergens such as group 1 and group 5 which show more cross-reactivity. Group 5 is the major allergen against which more than 90% of the patients are sensitized. In a recent study, sublingual immunotherapy (SLIT) tablets containing meadow grass along with other grasses, were compared with placebo. There was a reduction in the symptoms and rescue medication use along with a reduced number of adverse events. Cross-reactivity of Kentucky bluegrass is seen with all grasses, including wheat, other pollen, and some plant-derived foods.
Epidemiology
Worldwide distribution
In a Dutch study, extracts of about 17 pollens of various grass and corn species as well as recombinant allergens, specific IgE antibodies were found in 26.1% of the sera. Also, the highest response was measured against Kentucky bluegrass. In another Polish study, 22 patients were investigated for specific IgE antibodies to grass and weed pollens with seasonal allergic rhinitis. The result showed the most common sensitization to Meadow fescue, followed by Meadow grass.
Risk factors
Grass pollens are popularly known to be the risk factors for AR in the middle of the 19th century. Grass pollens are known to be the most predominant seasonal aeroallergens that cause allergic symptoms such as allergic rhinoconjunctivitis (ARC) and asthma during summer in cool temperate climates. Majority of the grass species are fertilized by wind and emit allergenic pollens extensively during their peak flowering season.
Pediatric issues
In a recent study, continuous exposure to this pollen during the period of first 6 months of birth resulted in the sensitization for them at 2 years and the development of asthma as well as allergic rhinitis (AR) eventually in their childhood. Additionally, children who were born during the pollen season had a higher risk of developing allergic disease subsequently in their childhood without their parents having asthma.
Route Of Exposure
Main
The route of exposure is mainly inhalation. Grass pollen is one of the major reasons behind IgE-associated allergy around the world. The inhalation of grass pollen often results in acute inflammatory conditions such as conjunctivitis, asthma, and AR in sensitized individuals.
Clinical Relevance
IgE mediated reactions
Grass pollen allergy mainly causes allergic rhinitis and exacerbation of asthma.
Allergic rhinitis (AR)
In one Polish study, 22 patients were investigated for specific IgE antibodies to grass and weed pollens with seasonal AR. The result showed the most common sensitization to Meadow fescue (Festuca elatior) followed by Kentucky blue.
Prevention And Therapy
Seasonal allergic rhino-conjunctivitis affects millions of people around the world. A multicentric, randomized, double-blind and placebo-controlled study was conducted to investigate the role of sublingual immunotherapy (SLIT) tablets containing freeze-dried allergen extracts of 5 kinds of grass such as cocksfoot, Kentucky bluegrass, ryegrass, sweet vernal grass and timothy grass as compared to placebo. The results indicated a reduction in the symptoms and use of rescue medications along with a lower number of adverse events.
Cross-Reactivity
Meadow grass contains major allergens such as group 1 and group 5 which show more cross-reactivity. Group 5 is the major allergen against which more than 90% of the patients are sensitized. A monoclonal human IgE antibody shows cross-reactivity between group 5 allergens and other grass and corn plants. Another study found the existence of group 5 allergens in Kentucky bluegrass as well as other grasses such as timothy, cocksfoot and ray.
References
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