Table of Contents

Whole Allergen

t11 Maple leaf sycamore, London plane Pollen

t11 Maple leaf sycamore, London plane Pollen Scientific Information

Type:

Whole Allergen

Display Name:

Maple leaf sycamore, London plane Pollen

Allergen code:

t11

Family:

Platanaceae

Species:

Platanus acerifolia

Route of Exposure:

Inhalation

Latin Name:

Platanus acerifolia

Other Names:

Maple leaf sycamore, London plane tree, American sycamore

Summary

London plane tree (Platanus acerifolia) is a wind-pollinated, deciduous tree that can attain a height of around 30 m. It is also known by the name Platanus Hybrida, as it is a hybrid of tree species P. orientalis and P. occidentalis. This tree can be found in abundance as an ornamental tree around urban streets, parks, and avenues. It is especially prevalent in Europe, North America, West Asia, South Africa, Australia, and New Zealand. Exposure to plane tree pollen might induce allergic reactions like asthma, rhinitis, and conjunctivitis among sensitive individuals. The allergenic components Pla a 1, Pla a 2, and Pla a 3 have been identified from the London plane tree pollen and listed in the IUIS database. Pla a 1, Pla a 2, and Pla a 3 have been established as significant diagnostic markers in Platanus-allergic patients. London tree pollen has exhibited cross-reactivity with tree pollens (like hazel, alder, birch), grass pollens (like maize, American cotton), food (like peach, tomato, hazelnut, banana), and fungi (like Alternaria alternata).

Allergen

Nature

London plane is a large-sized, deciduous, wind-pollinated tree that grows up to a height of 21-30 m. The tree possesses a wide extending structure with weighted and hanging branches. The bark of this tree has a patterned combination of cream, olive, grey, and light brownish color. The leaves are triangular-ovate (maple-like shape), medium to dark greenish with a matt to glossy finish on the upper surface, and light-greenish on the underneath surface. During autumn (fall), the leaves changes to yellowish-brown in color (1). The flowers are monoecious, and after pollen shedding, the male flower heads fall off (2). Pollen dispersal of the London plane tree begins in the spring and lasts for up to 20 - 40 days (3). This tree is abundantly found as an ornamental tree (4) in parks, avenues, and streets due to its high tolerance to urban conditions (2).

Habitat

This tree can thrive in areas with abundant sunlight and is highly drought tolerant. Well-drained, clay, sandy, loamy soil is reported to be optimal for the London plane tree's growth. It can sustain in both acidic as well as alkaline soil and extended flooding conditions. This tree is moderately tolerant towards aerosol salt in the soil composition (5).

Taxonomy

London plane tree (Platanus acerifolia), also known as Platanus Hybrida (6), belongs to the Platanaceae family. This genus Platanus possesses around 10 allergenic and highly cross-reactive species (7). This tree is a hybrid tree of P. orientalis and P. occidentalis (8).

Taxonomic tree of London plane tree (9)
Domain	Eukaryota
Kingdom	Plantae
Phylum	Spermatophyta
Subphylum	Angiospermae
Class	Dicotyledonae
Order	Hamamelidales
Family	Platanaceae
Genus	Platanus
Species	Platanus acerifolia

Tissue

London plane tree pollen is a spheroidal monad (16–22 μm in length), tri-grooved (tricolpate), tectate-columellate, webbed surface with a thick (tectum-like) base layer. The pollen from this tree is considered to be highly allergenic (1). Pla a 1, Pla a 2, and Pla a 3 have been identified as potential allergenic molecules from London plane tree pollen and listed in the IIUIS database (10).

Epidemiology

Worldwide distribution

The concentration of London plane tree (Platanus) pollen is high during the spring season in countries like Europe, North America, and Australia. In Sydney, often exposure to London Plane tree pollen is speculated to be linked with conditions like conjunctivitis, rhinitis, and respiratory irritations (11).

A Spanish aerobiological pollen sampling study confirmed 14.9% as total annual pollen count (mean of 1979-1993) for Platanus (London plane) tree pollen in the air (6).

Reports published from 1994-2005 have indicated the prevalence of London plane tree pollen sensitization of up to 8.48% in Barcelona, Spain, 11.4% in Cova da Beira, Portugal, and 56% in Madrid, Spain (11).

In Mediterranean European regions, the prevalence of sensitization towards Platanus (London plane) tree pollen grains has been reported to range between 3% - 52% (12).

An Australia-based study reported a positive skin prick test (SPT) towards Platanus (London plane tree) in 23.6% (13/55) of atopic patients with respiratory symptoms (13).

Sensitization rate of 22% towards London plane tree (Platanus Acerifolia) pollen allergen was reported in a study conducted in South Africa on 50 allergic rhinitis patients (14).

Environmental Characteristics

Worldwide distribution

Uncertainty prevails with regards to the origin of the hybris London plane tree. This tree is prevalent (especially in urban regions) in North America, Europe (south and central), Australia, New Zealand, South Africa, and western Asia. More than 50% of the tree found in the London streets are Plane trees, and therefore, this tree is regarded as the London plane tree (1).

Route of Exposure

Main

The route of exposure for London tree plane tree pollen is through inhalation (11).

Clinical Relevance

According to a study, the concentration of aeroallergen (like pollen from the London tree plane) is claimed to be related to the symptoms of allergic disease. For certain sensitized patients, plane tree pollen-mediated clinical symptom of allergic diseases is evident with an exposure concentration of 16 pollen grains per m³ of air (threshold value). While, for a majority of the sensitized patients, these clinical symptoms are evident with an exposure concentration of 91 pollen grains per m³ of air (2).

Exposure to London tree pollen may induce allergic symptoms like rhinitis, conjunctivitis (11), and asthma (6).

Allergic rhinitis (AR)

An Australia-based study was conducted on 64 individuals with a history of seasonal rhinitis (speculated to be triggered by Platanus pollens). 23.4 % (15/64) individuals exhibited positive SPT towards Platanus (London plane tree) pollen extract (11).

A retrospective, descriptive study conducted on 100 patients diagnosed with AR exhibited nasal obstruction as a frequent symptom in 80% of the patients, postnasal drip in 21%, itching in 39%, sneezing in 40%, and rhinorrhea in 58%. Out of these, 25% (25/100) of the patients showed sensitivity towards London plane tree pollen allergen (15).

Allergic Rhino-Conjunctivitis (ARC)

A study was conducted on 47 Spanish patients with a history of perennial or seasonal rhinitis and/or asthma. 74% of patients exhibited positive SPT towards London plane tree (Platanus hybrida) pollen. Clinical manifestation of conjunctivitis was evident among 78% of the patients who exhibited a positive SPT (n=36) towards London plane (Platanus) tree pollen (16).

Asthma

A Spanish study conducted on 187 patients with rhinitis and/or asthma (seasonal) reported positive SPT in 56% of the patients. 3 out of 5 patients in the control group developed immediate weal-and-erythema (Skin test) and significant IgE-reactivity towards Platanus hybrida (London plane tree) pollen. Additionally, a significant correlation (p < 0.001) was also reported between Platanus pollen count and bronchial asthma among these 3 patients (6).

Prevention and Therapy

Prevention strategies

Avoidance

One of the main measures to be taken is to reduce the amount of pollen entering the respiratory system. During pollen season, allergic patients are suggested to stay indoors or wear a mask outdoors to keep away from pollen allergens. In worsening conditions, patients may be advised to move to a non-pollen area (17).

Molecular Aspects

Allergenic molecules

Pla a 1, Pla a 2, and Pla a 3 allergens from London plane tree (Platanus acerifolia) pollen have been identified and listed in the IUIS database (10).

Allergen	Biochemical Name	Molecular Weights (kDa)	Allergenicity
Pla a 1	Putative invertase inhibitor	18	87% of 30 sera from Platanus-allergic patients recognized Pla a 1 protein (18).
Pla a 2	Polygalacturonase	43	84.6% (22) of 26 sera from patients with P.acerifolia allergy exhibited specific-IgE reactivity towards Pla a 2 protein (19).
Pla a 3	Non-specific lipid transfer protein 1 (LTP)	10	44.8% (26) of 58 sera from plane pollen-allergic patients exhibited IgE antibody reactivity towards nPla a 3 (20) 53% of sera from plane tree pollen allergic patients with associated peach allergy recognized Pla a 3 protein (21).

Allergen

Biochemical Name

Molecular Weights (kDa)

Allergenicity

Pla a 1

Putative invertase inhibitor

87% of 30 sera from Platanus-allergic patients recognized Pla a 1 protein (18).

Pla a 2

Polygalacturonase

84.6% (22) of 26 sera from patients with P.acerifolia allergy exhibited specific-IgE reactivity towards Pla a 2 protein (19).

Pla a 3

Non-specific lipid transfer protein 1 (LTP)

44.8% (26) of 58 sera from plane pollen-allergic patients exhibited IgE antibody reactivity towards nPla a 3 (20)

53% of sera from plane tree pollen allergic patients with associated peach allergy recognized Pla a 3 protein (21).

Biomarkers of severity

Pla a 1 is recognized in approximately 90% of the plane tree allergic patients and is considered a major marker allergen from the plane tree (7).

Pla a 2 is reported in more than 84% of P.acerifolia pollen-allergic patients and is also considered an important allergen from P. acerifolia (London plane tree) pollen (19).

Pla a 3 is observed in 53% of plane tree pollen and peach allergic. The study revealed Pla a 3 to be a competent diagnostic marker for patients with plane pollen and peach allergy (21).

Cross-reactivity

A study reported cross-reactivity between plane tree pollens and other tree pollens like chestnut, oak, hornbeam, hazel, alder, and birch (2).

A number of studies reported cross-reactivity between pollen from the genus Platanus and Chenopodiaceae, Artemisia, Poaceae, Plantago, Parietaria, , Olea, Betula, and Cupressus species pollen (22).

ELISA inhibition testing on Platanus-allergic individuals’ sera has exhibited significant cross-reactivity with grasses (18).

As per protein homology study Pla a 2 demonstrated identical residues of polygalacturonase in pollens like Zea mays (maize; 43%), Gossypium hirsutum (American cotton; 48%), Brassica napus (rape; 49%), Oenothera organensis (evening primrose; 56%) and food like tomato (37%), apple (38%), kiwi (39%), peach (42%). Similar protein homology was also observed in Japanese cedar pollen allergen (Cry j 2; 34%) (19).

Pollen from the plane tree (Pla a 3) is reported to be cross-reactive with hazelnut, banana, celery, and peanut (23).

LTP from Plane tree (Pla a 3) is reported to exhibit sequence similarity of 58.3% with peach LTP (Pru p 3) (20)

Significant correlation between plane tree pollen allergen rPla a 2 and fungal allergens rAlt a 6 (Alternaria alternata; p = 0.008) and rCla h 8 (Cladosporium herbarum; p = 0.010) has been reported in a study. Further, rPla a 3 has exhibited significant association with rCla h 8 (p = 0.003) (24).

Compiled By

Author: Turacoz Healthcare Solutions

Reviewer: Dr. Fabio Iachetti

Last reviewed: January 2021

References

Oh J-W. Pollen allergy in a changing world: Springer; 2018.
Puc M, Magyar D, Udvardy O, Lipiec A, Rapiejko P, Siergiejko G, et al. Plane tree pollen season in Poland and Hungary in 2019–why are the plane trees planted in cities so much? Alergoprofil. 2020;16(1):15-20.
Chen Z, Yang Y, Chen X, Wu Z, Li S. Characterization of two pollen allergens of the London plane tree in Shanghai. Iranian Journal of Allergy, Asthma and Immunology. 2015:139-48.
Ni WW, Wang LB, Zhou YJ, Cao MD, Huang W, Guo M, et al. Expression, purification and epitope analysis of Pla a 3 allergen from Platanus acerifolia pollen. Molecular Medicine Reports. 2017;16(3):2851-5.
Gilman EF, Watson DG. Platanus x acerifolia ‘Bloodgood’: ‘Bloodgood’ London Planetree. Environmental Horticulture. 2014(UF/IFAS Extension).
Subiza J, Cabrera M, Valdivieso R, Subiza JL, Jerez M, Jiménez JA, et al. Seasonal asthma caused by airborne Platanus pollen. Clin Exp Allergy. 1994;24(12):1123-9.
Gangl K, Niederberger V, Valenta R, Nandy A. Marker allergens and panallergens in tree and grass pollen allergy. Allergo Journal International. 2015;24(5):158-69.
Enrique E, Cistero-Bahima A, Bartolome B, Alonso R, Miguel-Moncin MS, Bartra J, et al. Platanus acerifolia pollinosis and food allergy. Allergy. 2002;57(4):351-6.
CABI. London Plane tree 2019 [12-01-2021]. Available from: https://www.cabi.org/isc/datasheet/42241#toidentity.
WHO/IUIS. Allergen Nomenclature 2019 [12-01-2021]. Available from: http://www.allergen.org/search.php?allergensource=Platanus+acerifolia.
Sercombe JK, Green BJ, Rimmer J, Burton PK, Katelaris CH, Tovey ER. London Plane Tree bioaerosol exposure and allergic sensitization in Sydney, Australia. Annals of Allergy, Asthma & Immunology. 2011;107(6):493-500.
Fernández‐González D, González‐Parrado Z, Vega‐Maray A, Valencia‐Barrera R, Camazón‐Izquierdo B, De Nuntiis P, et al. Platanus pollen allergen, Pla a 1: quantification in the atmosphere and influence on a sensitizing population. Clinical & Experimental Allergy. 2010;40(11):1701-8.
Burton P. Description of Platanus (London Plane Tree) Pollen Levels and Pollen Sensitization in an Australian Population. Journal of Allergy and Clinical Immunology. 2006;117(2):S112.
Seedat R, Claassen J, Claassen A, Joubert G. Mite and cockroach sensitisation in patients with allergic rhinitis in the Free State. South African Medical Journal. 2010;100(3).
Joubert G. Allergen sensitivities of patients with allergic rhinitis presenting to the ENT Clinic, Universitas Academic Hospital. Current Allergy & Clinical Immunology. 2006;19(3):130-2.
Varela S, Subiza J, Subiza JL, Rodríguez R, García B, Jereza M, et al. Platanus pollen as an important cause of pollinosis. Journal of allergy and clinical immunology. 1997;100(6):748-54.
Xie Z-J, Guan K, Yin J. Advances in the clinical and mechanism research of pollen induced seasonal allergic Asthma. American journal of clinical and experimental immunology. 2019;8(1):1.
Asturias J, Ibarrola I, Bartolome B, Ojeda I, Malet A, Martinez A. Purification and characterization of Pla a 1, a major allergen from Platanus acerifolia pollen. Allergy. 2002;57(3):221-7.
Ibarrola I, Arilla MC, Martínez A, Asturias JA. Identification of a polygalacturonase as a major allergen (Pla a 2) from Platanus acerifolia pollen. Journal of allergy and clinical immunology. 2004;113(6):1185-91.
Lauer I, Miguel-Moncin MS, Abel T, Foetisch K, Hartz C, Fortunato D, et al. Identification of a plane pollen lipid transfer protein (Pla a 3) and its immunological relation to the peach lipid-transfer protein, Pru p 3. Clin Exp Allergy. 2007;37(2):261-9.
Wangorsch A, Larsson H, Messmer M, García‐Moral A, Lauer I, Wolfheimer S, et al. Molecular cloning of plane pollen allergen Pla a 3 and its utility as diagnostic marker for peach associated plane pollen allergy. Clinical & Experimental Allergy. 2016;46(5):764-74.
Fernández-González M, Guedes A, Abreu I, Rodríguez-Rajo F. Pla a_1 aeroallergen immunodetection related to the airborne Platanus pollen content. Science of the total environment. 2013;463:855-60.
Popescu F-D. Cross-reactivity between aeroallergens and food allergens. World journal of methodology. 2015;5(2):31.
Čelakovská J, Bukač J, Vaňková R, Krcmova I, Krejsek J, Andrýs C. Sensitisation to molecular allergens of Alternaria alternata, Cladosporium herbarum, Aspergillus fumigatus in atopic dermatitis patients. Food and Agricultural Immunology. 2019;30(1):1097-111.