Types of food allergies
Commonly mechanisms due to food allergies and the resulting classification made on the basis of the etio-pathological mechanisms is divided into three categories:
- IgE-mediated
- non-IgE mediated,
- mixed.
In addition, the presence of other immune factors in food can also contribute to raising immunological gender. For example, the allergen is a glycoprotein of peanut ( Ara h 1 ) that not only is awfully steady and opposing to heat and digestive-enzyme deprivation, but also acts as an adjuvant of T-lymphocytes helper2 (TH2) due to the expression of a "glycan adduct". The ' innate immunity in the intestine is represented by: natural killer cells , polymorphonuclear leukocytes , macrophages , epithelial cells in fell'orletto spazola, Toll-like receptors and acquired immunity, however, is represented by lymphocytes from the intraepithelial and lamina propria , from Peyer's patches , the IgA , and cytokines , together provide a barrier that can block the entry of antigens.
It is known that food allergy is more common in children: in fact most of the intestinal mucosal permeability in infants and early exposure to allergenic antigens have been proposed as a possible cause of sensitization in infants. However, it was shown that the gastrointestinal mucosa reaches its full maturity in terms of permeability after only 2-3 days after birth and the increased permeability observed in some children with food allergy seems to be more a consequence than the cause of the response inflammatory-type reactions.
In contrast, early exposure to foods may prevent the development of food allergies in some conditions. This is suggested by a recent study has shown that Israeli children, who often consume a popular snack of peanut before 1 year of age, have a prevalence 10 times lower in developing peanut allergies than children of Member U.S. and UK, where peanuts are consumed rarely before 12 months of age, have been proposed for this reason, other additional factors as needed to overcome the physiological oral tolerance.
Among the factors that can reduce food tolerance to food allergens include:
- the increased permeability of the intestinal inflammatory mucosa;
- the increased permeability of the intestinal mucosa due to irritative phenomena to drugs (aspirin);
- the presentation of food-proteins for alternative routes such as skin or respiratory mucosa. In about one third of children with coexisting food allergy asthma ;
- altering the balance between TH2 and immunological ' major histocompatibility antigen (MHC). Often due to recruitment of proteins of cow's milk during lactation
Among the factors triggering food have recently been hypothesized as a cause of allergies:
- decrease in immunological competence against generally bacteria / viruses / worms (the so-called hygiene hypothesis );
- imbalance in favor of omega-6 at the expense of omega-3 ;
- reduction in the intake of dietary antioxidants and increase / decrease of vitamin D in the diet.
They are less well characterized, but are usually due to an acute or chronic inflammation in the gastrointestinal tract where eosinophils and T cells appear to play an important role in the genesis of pathological event. In patients with food.induce enterocolitis TNF-α plays an important role: in fact, it can be measured in vitro in monocytes of children with food protein-induced enterocolitis. Chung and contemporaries furthermore found increased discoloration for TNF-α in duodenal biopsies of children with food-induced enterocolitis.
For mixed forms such as eosinophilic esophagitis, eosinophils, and chemoattractants play a key role. In these subjects the eotaxin-3 is over expressed in 50% of the esophageal tissue compared to controls with chronic esophagitis.
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