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Whole Allergen

g8 Meadow grass (Kentucky blue)

g8 Meadow grass (Kentucky blue) Scientific Information

Type:

Whole Allergen

Display Name:

Meadow grass (Kentucky blue)

Route of Exposure:

Inhalation

Family:

Poaceae (Gramineae)

Species:

Poa pratensis

Latin Name:

Poa pratensis

Other Names:

Smooth Meadow grass,Spear Grass, June Grass

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. 

Allergen

Nature

Kentucky bluegrass (Poa pratensis L.) is a cold temperature, perennial, short-to-medium length, long-lived, extremely palatable grass with soft green leaves having boat-shaped tips. It is widely spread alongside rhizomes to create a dense sod. It flourishes best in the cold weather with fertile soils that have a pH between 6 and 7. It is generally grown in the whole United States, however, it is the principal agricultural plant in the north-central and north-eastern parts. It has accommodated to the regions with the average daily temperature in July not exceeding 75°F (1, 2).

Habitat

Kentucky bluegrass prevails in the areas with a cold and humid environment.  It is also spread in the high and low elevated prairie areas.  In the western parts, it is seen in medium to high elevated regions. In California, it is seen in the mountains which have cool regions. It is commonly seen as a forest floor plant in an aspen environment that is spread in the areas of intermountain, ponderosa pine, bunchgrass, and riparian areas.  It is also commonly found in the dominant of Midwestern prairies (3). However, due to its formidable impact on the ecosystem as well as its widespread invasion into the natural areas and changes in the climatic conditions, the effective management strategies are important (1).

Taxonomy

The majority of the grass species are divided into three subfamilies:  Pooideae, Chloridoideae and Panicoideae (4).

Taxonomic of Meadow grass    
Domain Eukaryota
Kingdom Plantae
Phylum Spermatophyta
Subphylum Angiospermae
Class Monocotyledonae
Order Poales
Family Poaceae
Genus Poa
Species P. pratensis
Taxonomic of Meadow grass    

 

Tissue

The roots of Kentucky bluegrass are superficial with an uppermost limit of around 8 cm from the ground surface. Stems are about 30-90 cm in height. The leaves are joined by the base of the stem, they are often bent and occasionally bushy at the joint. They have even blades which are about 2 to 5 mm in width and 10 to 40 cm in length. The inflorescence is an open tuft made up of around 2 to 6 flowers. The lemmas contain a bunch of flimsy hairs. The flowering season generally begins in May with the ripening of fruit by mid of June (3).

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 (5). 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 (6).

Risk factors

Grass pollens are popularly known to be the risk factors for AR in the middle of the 19th century (7). 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 (8).

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 (9). 

Environmental Characteristics

Worldwide distribution

The exact origin of Kentucky bluegrass has been most probably assumed to be from the Northern Great Plains region in the second half of the 18th century. After a few years, it gained the title of “common southward to the central United States”. In the state of Iowa in the US, it was categorized as a weed. There were many incidences of Kentucky bluegrass invading prairies in southwestern parts of Minnesota and advancing towards the Nebraska region. It has the ability to continue its growth from the spring to fall season with the capacity to produce elongated leaves in a great amount. (1)  

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 (10).

Clinical Relevance

IgE mediated reactions

Grass pollen allergy mainly causes allergic rhinitis and exacerbation of asthma (11).

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 (6).

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 (12).

Molecular Aspects

Allergenic molecules

Kentucky blue contains allergens such as Poa p 1, Poa p 2, Poa p 5 including Poa p 5(a), Poa p 5(b) and Poa p 10  (8).

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. (13)

Compiled By

Author: Turacoz Healthcare Solutions

Reviewer: Dr. Fabio Iachetti

 

Last reviewed: October  2020

References
  1. Dekeyser E. Kentucky bluegrass (Poa pratensis L.) Invasion in the Northern Great Plains: A Story of Rapid Dominance in an Endangered Ecosystem. Invasive Plant Science and Management 8(3):150401074913002. 2015.
  2. Hall MH. Agronomy Facts 50 Kentucky Bluegrass. 1996.
  3. Wennerberg S. Plant Guide. 2004.
  4. Kleine-Tebbe J. GRASS POLLEN ALLERGENS: Global Atlas of Allergy; 2015. Available from: http://www.dgaki.de/wp-content/uploads/2015/05/GRASS-ALLERGENS-Chapter-3g-in-GlobalAtlasofAllergy-EAACI-2014.pdf.
  5. 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.
  6. Silny W, Kuchta D, Siatecka D, Silny P. [Antigen specific immunoglobulin E to grass and weed pollens in the plasma of patients with seasonal allergic rhinitis]. Otolaryngol Pol. 1999;53(1):55-8.
  7. Bousquet J, Khaltaev N, Cruz AA, Denburg J, Fokkens WJ, Togias A, et al. Allergic Rhinitis and its Impact on Asthma (ARIA) 2008 update (in collaboration with the World Health Organization, GA(2)LEN and AllerGen). Allergy. 2008;63 Suppl 86:8-160.
  8. Andersson K, Lidholm J. Characteristics and immunobiology of grass pollen allergens. Int Arch Allergy Immunol. 2003;130(2):87-107.
  9. Erbas B, Lowe AJ, Lodge CJ, Matheson MC, Hosking CS, Hill DJ, et al. Persistent pollen exposure during infancy is associated with increased risk of subsequent childhood asthma and hayfever. Clinical & Experimental Allergy. 2013;43(3):337-43.
  10. Beggs PJ, Katelaris CH, Medek D, Johnston FH, Burton PK, Campbell B, et al. Differences in grass pollen allergen exposure across Australia. Aust N Z J Public Health. 2015;39(1):51-5.
  11. Davies JM. Grass pollen allergens globally: the contribution of subtropical grasses to burden of allergic respiratory diseases. Clin Exp Allergy. 2014;44(6):790-801.
  12. Didier A, Worm M, Horak F, Sussman G, de Beaumont O, Le Gall M, et al. Sustained 3-year efficacy of pre- and coseasonal 5-grass-pollen sublingual immunotherapy tablets in patients with grass pollen-induced rhinoconjunctivitis. J Allergy Clin Immunol. 2011;128(3):559-66.
  13. Flicker S, Vrtala S, Steinberger P, Vangelista L, Bufe A, Petersen A, et al. A human monoclonal IgE antibody defines a highly allergenic fragment of the major timothy grass pollen allergen, Phl p 5: molecular, immunological, and structural characterization of the epitope-containing domain. J Immunol. 2000;165(7):3849-59.
  14. Gangl K, Niederberger V, Davies J, Valenta R, Nandy A. Marker Allergens and Panallergens in Tree and Grass Pollen Allergy. 2017. p. 203-26.