DIETARY PLANT ALLERGENS - ASSOCIATED ALLE RGIES AND CROSS-REACTIONS

Plant allergens (PA) are considerably more numerous than animal allerg ens, although they represent only a small proportion of plant proteins . Many of them are proteins which have been preserved during the cours e of evolution: profilins, PR proteins, storage proteins, stress prote ins, enzymes, calcium-binding proteins. Their epitopes are sequential or conformational. The allergenic risk of a food protein is characteri zed by its thermal behaviour, resistance to digestion, and stability i n acidic medium. These tests are used to evaluate transgenic proteins. The analysis of 509 cases of food allergy (FA) collected by the Cercl e d'Investigations Cliniques et Biologiques en Allergologie (Allergolo gical Clinical and Laboratory Investigations Croup shows that PA are i nvolved in 50 per cent of cases. The oral syndrome and recurrent angio neurotic oedema are significantly mol-e frequent than in allergies to animal allergens, while the frequency of anaphylactic shock and asthma is identical, Allergy to PA represents 4 per cent of cases of FA to a single type of allergen before the age of 1 year, 28 per cent from 1 to 3 years, 54 per cent from 3 to 6 years, 61 per cent from 6 to 15 ye ars, and 80 per cent over the age of 15 years. PA are peanuts (142), r osaceae (34), umbelliferae (20), avocado, kiwi, banana, chestnut (22). The frequency of PFA is significantly related to pollinic sensitizati on, in contrast with AFA. The frequency of homologies between pollens proteins and fruit and vegetable proteins accounts for the positive la boratory tests to these substances, due to a cross-reaction, in the ab sence of food allergy. Skin tests ore less often falsely positive and always identify more frequent cross-sensitization than with AA, which is why standardized provocation tests are the gold standard diagnostic test.