t205 Elder

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• Latin name: Sambucus nigra
• Family: Caprifolicaeae
• Common names: Elder, Common Elder, Elderberry
• Source material: Pollen

Allergen Exposure

Geographical distribution
The Elder tree and other species of Sambucus comprise fast-growing small trees or large shrubs, 1-4 m tall. The leaves are compound and contain 5-11 leaflets, with finely or sharply toothed margins, 4-13 cm long and 2-6 cm wide.

Numerous species of Elder tree or Elderberry grow in Europe and North America. The Elder tree is native to south-eastern Canada and most of the United States except for the Great Basin and the Pacific Northwest, and is found in Britain, Europe, Iraq and Turkey.

Large clusters of creamy-white flowers are produced in summer, followed in autumn by large bunches of shiny black Elderberries. The flowers are borne in large panicles, and are insect-pollinated. The flowers are small, white, and fragrant, in flat cymes. The fruits ripen in late fall and are usually purple-black, numerous, 4-6 mm in diameter. Only blue/black berries are medicinal; the red berries produced by some species are not medicinal.

Environment
Elder trees are usually found in floodplains or rich soil. In Europe they are often seen along fencerows and ditches and stream banks. Other areas these shrubs can be found in are hedgerows, scrub, woods, roadsides and waste places. Elderberry fruits are used for making pie, jam and wine.

Unexpected exposure
Fruits should not be eaten fresh in large quantities, as they are emetic. Elder flower extract, mostly from the European species S. nigra, is made into a drink. The leaves of American Elder are toxic.

Allergens
To date the following allergen has been characterised:

• Sam n 1, a 33.2 kDa, ribosomal inactivating protein, found in the pollen, flower and fruit (1).

Thaumatin-like proteins (TLPs) have been isolated and characterized from fruits and leaves of Elder tree. Ripening berries accumulated a fruit-specific TLP during the final stages of maturation. The leaves expressed a TLP that closely resembled the fruit-specific homologue. These thaumatin-like proteins shared a high sequence similarity with group-5 pathogenesis-related proteins (2). The clinical relevance of this protein was not evaluated, nor whether the allergenicity of these TLPs is similar to that of other TLPs.

Potential cross-reactivity

An extensive cross-reactivity among the different individual species of the genus could be expected (3).

Clinical Experience

IgE-mediated reactions
Anecdotal evidence suggests that asthma, allergic rhinitis and allergic conjunctivitis are possible following exposure to pollen from this tree; however, few specific studies have been reported to date. Patients suffering from allergic rhinoconjunctivitis and dyspnoea during summer may exhibit these symptoms after contact with flowers or dietary products of the Elder tree. Nine patients with a history of summer hayfever were tested in a routine setting for sensitization to Elder. 0.6% of 3,668 randomly tested patients showed positive skin prick test and/or IgE antibodies to Elder (1).

References:

1. Forster-Waldl E, Marchetti M, Scholl I, Focke M,
   Radauer C, Kinaciyan T, Nentwich I, Jager S, Schmid ER, et al. Type I allergy to elderberry (Sambucus nigra) is elicited by a 33.2 kDa allergen with significant homology to ribosomal inactivating proteins.
   Clin Exp Allergy 2003;33(12):1703-10
2. Van Damme EJ, Charels D, Menu-Bouaouiche L,
   Proost P, Barre A, Rougé P, Peumans WJ. Biochemical, molecular and structural analysis of multiple thaumatin-like proteins from the elderberry tree (Sambucus nigra L.).
   Planta 2002;214(6):853-62
3. Yman L. Botanical relations and immuno-logical cross-reactions in pollen allergy. 2nd ed. Pharmacia Diagnostics AB. Uppsala. Sweden. 1982: ISBN 91-970475-09

2008

• References