A recent study published in Nature Medicine and signed-off on by a group from the University of Chicago and the University of Naples, has shown that food allergies originate in the intestine. However, talking about solving the riddle is a bit premature. Let’s see why.
First of all, as the authors themselves recall in the article, in recent years we’ve noticed an increase in food allergies in the population of Western countries. Their study focused on the early stages of childhood, during which there are many reasons that can contribute to the onset of one (or more) food intolerances. For example, changes in diet (including the Mother’s), the use of antibiotics, the increasing frequency of Caesarean Sections and breastfeeding.
There are therefore many factors that must be taken into consideration, however the experiments carried out by the two groups; one of which I remember being Italian, are quite interesting and innovative.
DIFFERENCES BETWEEN ALLERGIES AND INTOLERANCES
But let’s first spend a few words on the differences between allergies and food intolerances.
ALLERGIES are disorders due to food and caused by an immune response; usually this response is caused by type E immunoglobulin (IgE), which is also the only one to be detected by skin and blood tests.
INTOLLERANCES, on the other hand, don’t provide an immune response and can be of an enzymatic type (i.e. either a specific enzyme is not produced by the body or is not produced enough). Or, of a pharmacological type, where you do not necessarily have to ingest an actual drug, in order to demonstrate intolerance, but it’s enough that there is an active ingredient in a food, such as histamine, that’s present in nature — within the meat of some fish or cheese.
FOOD ALLERGIES AND EARLY CHILDHOOD
But back to the study of early childhood food allergies. The researchers focused on allergy to cow’s milk, or rather a protein contained in it, Beta-lactoglobulin. The first phase of the study focused on the analysis of the faeces of healthy children affected by cow’s milk allergy, finding a significant difference in the faeces microbiota. That is, in healthy subjects were identified bacteria that were associated with the lowest risk of developing food allergy (i.e. bacteria with a protective function).
The second phase of the study consisted of transplanting the microbiota from the faeces of sick children into sterile mice (that is, in whose intestines there were no microorganisms). This group of mice was then given the allergen (Beta-lactoglobulin), and the mice demonstrated the allergy. Other sterile mice were transplanted with mibrobiota from healthy children, and exposure to the allergen didn’t cause a reaction.
In addition, the researchers investigated the ileum in mice, the portion of the intestine in which food is absorbed and consequently the allergens, in a similar way to that in humans.
CLOSE TO A SOLUTION?
In scientific jargon we speak of up-regulation of the expression of certain genes in mice that had received the transplant from healthy children — and down-regulation, in mice that had received the microbial transplant from children with allergies. At this point, the researchers have narrowed the circle and have come to identify a bacterium, Anaerostipes caccae, which is part of the anaerobic Clostridia and is the most responsible for protection against anaphylactic response to food allergens.
In other words, there is a reasonable certainty that by administering the bacterium Anaerostipes caccae to children suffering from an allergy to cow’s milk, these children will no longer have the allergic reaction, or at least may have it in a very attenuated form; which would save them from an anaphylactic reaction in the case of accidental exposure to cow’s milk.
These studies represent a further step forward in the understanding of the mechanisms underlying the development of allergies — which seem to be more and more related to our second genome: the microbiota!
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