Latin name: Pinus strobus
Source material: Pollen
Common names: White pine, Eastern white pine, Northern white pine, Weymouth pine
Not to be confused with the Australian pine tree (Casuarina equisetifolia) t73.
Of the 100 different species included in the genus Pinus, almost all are found in the Northern Hemisphere, with 36 in North America. White pine is native to North America but is now found also in France, Mexico and Guatemala. Commercial cultivation was attempted in Europe but was given up because of a fungus disease.
White pine is a large, tall, evergreen conifer with an irregular or flattened dense crown. It can grow to 20 m tall in 40 years. White pine commonly reaches 200 years of age and may exceed 450 years. The bark is smooth and gray-green when young, becoming with age gray-brown and deeply furrowed, with broad ridges of irregularly rectangular, purple-tinged scaly plates. The distinctive whorled branching and 5 blue-green needles in each fascicle are characteristic of this tree. The needles turn chartreuse to golden-brown in autumn and abscise immediately.
White pine flowers are monoecious (male and female flowers are distinct but grow on the same tree), with staminate (male) flowers in clustered yellow catkins, and pistillate (female) flowers in pink immature cones. Pollen is shed between early April and the end of June, depending on latitude. The pollen count is often high. Cones ripen and seeds are dispersed from August through September, about 2 years after cone initiation. White pine begins producing cones when 5 to 10 years old. The winged seeds are about 2 cm long and are dispersed primarily by wind, up to 60 m within a stand and more than 210 m in the open.
White pine occurs in forests, is often planted for timber, and survives dry, sandy soils or mountainous conditions. This Pine is becoming rare because a severe fungus disease often infects it.
No allergens from this plant have yet been characterised.
An extensive cross-reactivity among the different individual species of the genus could be expected (1).
A high cross-reactivity among Pinus nigra, P. sylvestris, P. radiata and P. strobus has been demonstrated in inhibition studies (2).
As extensive cross-reactivity exists between Pine tree (P. radiata) and White pine tree (P. strobes), the following cross-reactivity patterns should be considered applicable to White pine tree.
IgE antibody studies have demonstrated that pollen extracts from Olive, Birch, Mugwort, Pine, and Cypress contain proteins that share common epitopes recognisable by sera from Olive-allergic individuals (3). Enzyme immuno-assay inhibition studies have revealed that leached P. radiata pollen proteins could partially inhibit serum IgE binding to Rye grass-specific IgE. This provides preliminary evidence for allergen cross-reactivity between these 2 unrelated species (4). The possibility of cross-reactivity between Pinus and Rye grass (Lolium perenne) has also been suggested (5).
Importantly, allergy to Pine nuts can occur with no symptoms of sensitisation to Pine pollen. Immunoblot experiments have demonstrated the presence of IgE antibodies in serum against several components of Pine nuts and pollen, with the presence of some cross-reacting components. The authors of this study suggest that development of Pine pollinosis may require a longer period of exposure to allergens, and that given the cross-reactivity between Pine nut and Pine pollen extracts, co-sensitisation to these 2 allergens could be possible (6).
Pinus pollen can induce asthma, allergic rhinitis and allergic conjunctivitis (7-9).
Pinus pollen allergy has been generally considered to be rare.
Although Pine pollen is released in large quantities, IgE-sensitisation to it has been found to occur in only 1.5%-3% of atopic patients in a northern Arizona private allergy practice, and in French studies (7-8).
This study reports that the incidence of positive skin testing to White pine in New England patients with spring seasonal allergic rhinitis was 6/61 (6%). Two of 4 patients challenged intranasally had a positive challenge (10).
A Spanish study suggests that Pine tree pollen is a significant aeroallergen and should be considered in investigations of pollen-allergic individuals. In this study, Pinus pollen (Pinus pinaster and Pinus radiata) was shown to be among the dominant pollens in an area of Spain. The majority of the patients were monosensitisated to Pinus pollen and suffered from seasonal rhinoconjunctivitis (9). The sensitising Pine pollen would in all instances depend on which species of Pine tree is present in the vicinity.
Other studies have shown that Pine tree pollen may be a significant aeroallergen. Airborne pollen contributors were measured in 2 locations in the USA, in Pennsylvania and New Jersey, separated by 11 km. Prominent airborne pollen included Pinus pollen. Tree, grass, and weed pollen season extended from mid-March to mid-June (11). In a study of aeroallergen sensitisation rates in children of the military in Texas, of 345 children who were skin prick-tested to a 51-allergen panel, 6.4% were positive to Pine (12).
In Burgos, Spain, Pinus spp. pollen was frequently detected in aerobiological studies (13). Pollen from Pinus spp. has also been documented in Portugal, with significant levels recorded in certain parts of the country (14-15). Pinus spp. pollen has also been documented in Trieste, Italy, with the level of this pollen being shown to correlate negatively with the winter severity (16).
As extensive cross-reactivity exists between Pine tree (P. radiata) and White pine tree (P. strobes), the latter should be found to generate similar clinical patterns to those the former generates.
Allergic contact dermatitis to White pine sawdust has been described (17). Contrary to the rarity of sensitisation to Pine pollen, workers processing Pine in sawmills showed a very high frequency of IgE sensitisation to the extract of Pine wood dust. This frequency was significantly greater than that of the sensitisation to Oak of workers processing Oak. (18) Airborne allergic contact dermatitis from Pine dust has been documented (19).
Compiled by Dr Harris Steinman, firstname.lastname@example.org
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