American researchers have found, where are the cells that trigger an allergic reaction to peanuts. It turned out that Allergy sufferers live in the intestines of peanut proteins recognizing b-lymphocytes (B-cells), which develop IgE — the immunoglobulin that is directly linked to allergies. They came from other local b-cells, which have switched from the production of safe classes of antibodies IgE. Variable sites of these antibodies was similar in different patients, which suggests that the proteins in peanut are recognized in a similar way. The results published in the journal Nature Immunology.
Food allergies can have different causes, but in most cases it is associated with incorrect production of IgE antibodies, which normally is intended to combat parasites like worms. In complex with antigens — pieces of protein such as worms or peanut — they activate fat cells and those in the answer instantly throw out stocks of Pro-inflammatory molecules. It serves as a signal to start the immune response, which in severe form of Allergy can lead to anaphylactic shock. Normal IgE is extremely small, but in the blood of people with allergies the amount of these antibodies is often not necessarily several times higher. Perhaps the concentration of these antibodies increased and in the meeting place of allergens and antibodies, but check it is not always easy because of the short life of IgE-producing cells and the difficulties with the sampling.
Ho Ramona (Ramona Hoh) from Stanford University and her colleagues suggested that in the case of food Allergy meeting of the antibodies, mast cells and antigens must occur somewhere in the gastrointestinal tract. To test this, they used a biopsy specimen of stomach and duodenal ulcers, 19 patients with allergies to peanuts. They found that in samples of these tissues the number of cells producing IgE, the Allergy is higher than that of people who have no allergies.
B cells with “wrong” antibodies can accumulate in the tissues in two ways. The first implies a constant replenishment of their numbers from the outside, and the second transformation is living in the tissue cells, so they switch to production of some immunoglobulins in other. To determine which of these paths is to blame for the peanut Allergy, the researchers found that the closest relatives of cells that synthesize IgE in the intestine. According to the results of immunoscintigraphy they were their neighbors, the intestinal b cells specializing in the production of antibodies IgA. This suggests that the development of IgE to blame mostly not “migrants”, and a reshaped local b cells.
The authors not only analyzed the repertoire of b-cells of individuals, but and compared them between patients. The formation of variable areas of immunoglobulins occurs in each person independently. Everyone has their own unique set of antibodies, but some of them may be similar due to convergence. It turned out that this is true for the antibody responsible for recognition of peanut protein Ara h2: similar DNA sequences found in different people, and as Allergy free, and healthy. In addition, in healthy these sequences are involved only in the “Assembly” of other classes of antibodies. That is for Allergy was not enough to “know” the protein of peanuts. Cells for this you need to switch from the production of non-allergenic classes of antibodies IgE.
Yet as the rescue of peanut Allergy are encouraged to use a method similar to those used in inhalation allergies (e.g. to pollen). The essence is that the patient takes the allergen for a long time in very low doses, and the immune system gets used to it. However, first tests have shown that even tiny amounts of peanut protein provoked a strong allergic reaction, and this treatment is not for everyone. Alternatively, other researchers are pinning their hopes on inhibitors of antibodies to peanut proteins. In this case they should contact the IgE, but did not lead to activation of mast cells.