Fruit allergyT78.1

The term fruit is a collective term for different parts of plants, fruits, pseudo-fruits and seeds. The distinction between fruit and vegetables is blurred. As a rule, fruit comes from perennial plants, vegetables from annual plants. Peppers, tomatoes, pumpkins, zucchini, aubergines and cucumbers are also part of fruit.

The division of fruit into groups of fruit species (pome fruit, stone fruit, exotic fruit, etc.) is the one commonly used in the trade. Thanks to its content of vitamins and mineral salts, fruit is an important food supplement (Franke W 1997).

The most important representatives belong to families (Jäger L et al. 2001):

• Rosaceae (apple, pear, quince, cherry, plum, apricot, peach, raspberry, strawberry, almond)
• Musaceae (banana)
• Bromeliaceae (pineapple)
• Caricaceae (Papaya)
• Rutaceae (orange, lemon, grapefruit, grapefruit)
• Saxifragaceae (Gooseberry, red currant)
• Punicaceae (pomegranate)
• Lauraceae (avocado, bay tree, cinnamon)

Cross-reactive allergic reactions can occur to varying degrees between the individual families, especially within the representatives of the individual families (Asero R et al. 2018). Even more important from an allergological point of view are the frequently occurring, unexpected cross-reactions between grass and tree pollen (especially birch) and the different types of fruit.

The allergens of the different types of fruit are increasingly found in the skin area. They are the result of localized accumulations of PR proteins (pathogenesis related proteins). PR proteins are produced by higher plants in response to infections by fungi, bacteria and viruses. So far, 14 such families have been identified. They show both functional and structural homologies and are thus also responsible for cross reactivities (pollen-fruit syndrome; latex-fruit syndrome). The PR-10 family is best known and probably has the greatest clinical significance. This family includes the Bet v-1 homologue proteins which are widely found in apple (Mal d 1), sweet cherry (Pru av 1), apricot (Pru ar 1), pear (Pyr c 1) as well as in birch pollen and the pollen of other fagal species.

Also of considerable cross-reactive importance are the lipid transfer proteins which are involved in defence reactions against pathogens as well as in the production of extracellular material such as cutin and waxes (Sánchez-Monge R et al. 1999). Lipid transfer proteins are major allergens of the pruneoideae (pear, apricot, plum and cherry). They are also found in tomato and corn. Like the Bet-v-1 homologous proteins, LTPs are mainly found in the outer skin, and less in the flesh of the fruit, which is important for their defence function.

Profilins, which influence the signal transduction of plants and play a role in the construction of the cytoskeleton, are responsible for cross-reactions between Bet-v-2 homologous structures in apple, pear (Pyr c 4), carrot, celery (Api g 4) and potato. They are also responsible for causing allergic reactions in lychee, tomato and pumpkin seeds.

The role of the isoflavone or phenylcoumarin-benzyl-ether-reductase homologues has not yet been finally clarified. In birch, the minor allergen Bet-v-6 belongs to this group. The pyr c 5 of the pear corresponds to it. Similar compounds are found in apple, pear and orange.

In Germany the average daily consumption of fruit and fruit products is 230 grams for men and 278 grams for women.

1. Asero R et al (2018) Allergy to LTP: to eat or not to eat sensitizing foods? A follow-up study. Eur Ann Allergy Clin Immunol 50:156-162.
2. Franke W (1997) Plant sciences: useful plants of temperate latitudes, subtropics and tropics. 6th edition, Thieme, Stuttgart
3. Jäger L et al (2001) Food allergens. In Jäger L et al (ed.) Food allergies and intolerances. Urban&Fischer Publisher p.136-137
4. Pastorello EA et al (1994) Allergenic cross-reactivity among peach, apricot, plum, and cherry in patients with oral allergy syndrome: an in vivo and in vitro study. J Allergy Clin Immunol 94:699-707.
5. Sánchez-Monge R et al (1999) Lipid-transfer proteins are relevant allergens in fruit allergy. J Allergy Clin Immunol 103:514-519.