Today, I would like to share information that will help you understand the results of an allergen chip analysis. In this article, we will examine the allergenic proteins (components) displayed on the allergen chip, which are responsible for various allergic reactions, ranging from oral itching to anaphylaxis. These proteins include peanuts, soy, wheat, nuts, fruits, animal fur, mold, and others.
We will also familiarize ourselves with the proteins that most commonly trigger asthma in allergic individuals and briefly discuss protein cross-reactivity.
For more information about protein properties and cross-reactivity, you can refer to my other articles on molecular diagnostics:
- Decoding the Allergen Chip
- Plant Proteins Causing Cross-reactivity (link)
- Proteins and Their Significance (link)
The allergen chip is truly a treasure trove of useful information. For those who are not yet familiar with it, here is a link to an article explaining what an allergen chip is.
By using the allergen chip and understanding which specific proteins elicit an allergic reaction in the body, it becomes possible to predict the severity of the reaction. Will the body develop swelling, or will it only result in unpleasant sensations in the mouth? This information is crucial because anaphylaxis is the most concerning aspect of allergies.
Proteins can be classified as thermally stable allergens, which withstand heating and the action of gastrointestinal enzymes, or labile allergens, which easily break down with heat treatment and enzymatic activity.
Thermally stable allergens often trigger severe reactions, such as anaphylaxis, while labile allergens may only cause local reactions (e.g., oral allergy syndrome – OAS – an unpleasant sensation in the mouth) or even remain asymptomatic.
This information allows for dietary adjustments instead of completely eliminating the allergenic food. We will know precisely what the body reacts to and avoid or learn how to prepare those specific ingredients properly.
FOOD ALLERGENS
Peanuts
Detection of IgE antibodies – antibodies to so-called storage proteins, such as Ara h 1, 2, and 3, indicates true peanut allergy, while sensitization to Ara h 8 (cross-reactive with PR-10 protein and Bet v 1) serves as a marker for mild symptoms. Sensitization to prof ilin or CCD is usually accompanied by only local oral symptoms or no reaction at all, and tolerance can develop to thermally processed peanuts.
Soy
Sensitization to Gly m 5 and/or Gly m 6 can cause a strong reaction, while sensitization to Gly m 4 (PR-10) only leads to oral allergy syndrome (OAS). However, in individuals with birch pollen allergy, consuming a large amount of lightly thermally processed soy (e.g., soy beverages) in the presence of sensitization to Gly m 4 (PR-10) can trigger severe clinical manifestations. Sensitization to prof ilin or CCD is usually accompanied by only local oral symptoms (OAS), and tolerance can develop to well-cooked soy.
Hazelnut
Sensitization to Cor a 1 (PR-10) causes local reactions of the oral allergy syndrome (OAS), while recognition by IgE antibodies to Cor a 8 (LTP) and storage proteins (Cor a 9 and Cor a 14) often leads to severe allergic manifestations, including anaphylaxis. Sensitization to prof ilin or CCD usually triggers only a local reaction, and tolerance can develop to thermally processed hazelnuts.
Walnut
Severe allergic reactions to walnuts are associated with sensitization to storage proteins (Jug r 1, Jug r 2) or LTP (Jug r 3). Sensitization to prof ilin or CCD usually triggers only a local reaction, and tolerance can develop to thermally processed walnuts.
Wheat
Sensitization to Tri a 19 is a risk factor for developing a severe allergic reaction. Wheat LTP (Tri a 14) cross-reacts with LTP from other food products. Sensitization to prof ilin or CCD usually triggers only a local reaction, and tolerance can develop to thermally processed wheat.
Rosaceae fruits
The family includes trees, shrubs, and herbs. It is one of the largest families of flowering plants, comprising about 100 genera and 3,000 species. Trees: pear, apple, cherry, black cherry, plum, peach, almond, apricot, rowan, medlar. Common shrubs of the Rosaceae family: blackberry, raspberry. Among the herbs, there is also strawberry. The Rosaceae family also includes ornamental shrubs such as rose hips, spirea, and hawthorn.
In individuals with allergy to these fruits, particularly in the case of sensitization to PR-10 proteins (Mal d 1, Pru p 1) or prof ilins (Pru p 4), a local reaction is more common because these proteins are destroyed by cooking and digestive enzymes.
Sensitization to LTP (Pru p 3), especially in residents of the Mediterranean coast, causes a wide range of allergic reactions (from asymptomatic to anaphylaxis) and is generally a marker of the risk of pronounced reactions, including anaphylaxis, triggered by other factors (physical activity, alcohol consumption, medication intake).
Eggs
A high level of IgE antibodies to ovomucoid (Gal d 1) is a risk factor for egg allergy, including those subjected to culinary processing. If the levels of these antibodies are below the diagnostic threshold, there is tolerance
Milk
IgE antibodies against casein (Bos d 8) and beta-lactoglobulin (Bos d 5) are markers of milk allergy, including boiled milk.
Fish
Parvalbumins (refer to the article “Proteins and their significance”) (Gad c 1 and Cyp c 1) serve as the main allergens in fish. They are typically heat-stable and resistant to digestive enzymes. Parvalbumins exhibit a wide range of cross-reactivity, so sensitization to one parvalbumin can lead to reactions to parvalbumins in other fish species (such as carp, cod, herring, flounder, mackerel, tuna, salmon, perch, and eel).
Shellfish
Allergic reactions to crustaceans are most often triggered by tropomyosin, which exhibits a broad spectrum of inter-species cross-reactivity, including with dust mites. Shrimp and other shellfish also contain other clinically significant allergens, such as sarcoplasmic calcium-binding protein and arginine kinase.
Meat
Galactose is found in the glycoproteins and glycolipids of non-human primates and monkeys, but not in humans. IgE antibodies that react to galactose can cause pronounced delayed-type reactions and anaphylaxis. Galactose residues are also present in cat secretions, which do not have high allergenic activity. Additionally, galactose is present in gelatin. Sensitization to galactose can be caused by tick bites or parasites. Clinical manifestations of galactose sensitization include delayed-type reactions in the form of anaphylaxis to red meat (beef, pork, lamb, venison). Galactose is also detected in the anti-cancer drug cetuximab (chimeric antibodies).
Bovine serum albumin (Bos d 6) is a heat-labile allergen found in milk and beef. Due to cross-reactivity, allergic reactions to meat from various mammals can occur.
INHALATION ALLERGENS
Animal Fur
A high level of IgE antibodies to Fel d 1 is associated with the development of asthma in patients with cat allergies. Interestingly, in Swedish children, severe asthma is provoked by the recognition of antibodies to three or more animal-derived allergens, such as lipocalins (Mus m 1, Equ c 1, Fel d 4, Can F 1 and 2), kallikrein (Can f 5), and secretoglobulin (Fel d 1).
Further research on animal allergies is always necessary since many patients are sensitized to multiple animal species. Moreover, cross-reactivity between cat, dog, and horse fur allergens is often difficult to determine even at the molecular level.
Pollen
Sensitization to specific allergens can serve as a marker for more severe pollen allergies, increasing the risk of systemic reactions during immunotherapy. For example, Ole e 9 and pollen-derived lipid transfer protein (LTP) Ole e 7 have been associated with increased risk. Sensitization to profilin is commonly found among patients with pollen allergies and is usually accompanied by milder allergy symptoms. However, in some cases, profilin can be a risk factor for pronounced reactions in olive and other plant allergies (such as melons and lemons).
Mites
Although no specific sensitization profile is considered a risk factor for lower respiratory tract diseases or their severity, an elevated IgE/IgG4 ratio for Der p 2 is associated with asthma. In the case of mite allergies, Der p 10 (tropomyosin) is a minor allergen but may indicate the risk of allergic reactions to shrimp and snails, which can have a severe course.
Mold
Hypersensitivity reactions to Aspergillus fumigatus and IgE reactivity to Asp f 2, 4, and 6 indicate bronchopulmonary aspergillosis (a chronic infectious-allergic disease of the bronchi and lungs). Sensitization to Asp f 1 and/or Asp f 3 suggests allergic asthma.
Cockroaches
Recent studies have shown that sensitization to Per a 2 is associated with severe respiratory allergic diseases in individuals with cockroach allergies. Currently, the allergen Per a 2 is not commercially available for testing, but its homolog, Bla g 2, exists. Cockroaches also contain cross-reactive tropomyosin (Bla g 7), which indicates the risk of allergic reactions to shrimp or snails, which can have a severe course.
OTHER ALLERGENS
Latex
The cross-reactive allergen responsible for the development of the so-called latex-fruit syndrome has not yet been determined, although there is an opinion that it may be Hev b5, 6, and 11.
Hymenoptera Venom
Most allergens in hymenoptera venom are cross-reactive carbohydrate determinants (CCDs), which to some extent contribute to the clinically insignificant phenomenon of IgE cross-reactivity between bee and wasp venom. For patients with positive results in traditional IgE tests that use allergen extracts, the detection of recombinant hymenoptera venom allergens can help differentiate true sensitization from cross-reactivity caused by CCDs (see article “Proteins and their significance”).
This article was written with the help of a publication from the website aalu.org.ua (WAO-ARIA-GALEN Consensus on Molecular Diagnosis of Allergy).