How dogs protect children from asthma and colds
An explanation for the antiallergic effect of dogs on children has been found
News from UCSF: Research Shows How Household Dogs Protect Against Asthma and InfectionThe constant presence of a dog in the house in a special way changes the composition of the intestinal microflora of the child, reducing the severity of the immune response to allergens.
This is the biological mechanism that explains why children who have been in contact with domestic dogs since birth are much less likely to suffer from pollinosis, asthma and other types of allergic diseases, the authors of the study published in the journal Proceedings of the National Academy of Sciences (Fujimura et al., House dust exposure mediates gut microbiome Lactobacillus enrichment and airway immune defense against allergens and virus infection). Scientists also managed to identify lactobacillus, whose presence in the microbiome plays a key role in protecting the respiratory tract from allergens and.
Previous studies by both American and European experts have shown that the presence of a dog in the house reduces the likelihood of developing allergies in a child due to early contact of his immune system with a variety of allergens that enter the house on the paws and fur of pets.
Since the connection between the composition of the intestinal microflora and the severity of the immune response to foreign agents has already been proven, a multidisciplinary group of researchers from the Universities of California and Michigan, led by microbiologist Susan Lynch, tried to clarify the processes underlying the "dog–child – allergy protection" phenomenon in a mouse model.
Lynch and her colleagues collected dust samples in homes where there are no pets, and in homes where a dog who regularly walks on the street lives as a pet. The dust mixed with water was fed to young individuals, and then they provoked an immune response with the help of crushed cockroaches and egg white – two substances that cause respiratory allergic reactions in both rodents and humans.
Mice exposed to house dust, not associated with the presence of a dog, showed a reaction similar to allergies in humans, accompanied by a runny nose and increased immune activity in the respiratory tract. At the same time, in animals that received dust from "dog" houses, the allergic reaction was either reduced or not observed at all. In such mice, a significant decrease in the total number of activated T cells, the release of anti-inflammatory Th2 cytokines and the secretion of tracheobronchial mucus was noted, which indicates a decrease in the activity of the immune system.
The study of the composition of the intestinal microflora of mice before and after exposure to dust showed that the bacterium Lactobacillus johnsonii is abnormally widespread in the intestines of "protected" animals. The introduction of this bacterium into the diet of mice not participating in this experiment reduced the level of allergic reaction in the respiratory tract mucosa in the latter and even protected the animals from respiratory syncytial virus (RSV), infection of which in infancy increases the risk of asthma in older age. It was found that the presence of Lactobacillus johnsonii is associated with a significant decrease in the number and proportion of activated killer cells of the immune system - T lymphocytes of the CD11c+/CD11b+ and CD11c+/CD8+ subtypes, as well as a decrease in the expression of Th2 cytokines in the respiratory tract.
"These results suggest that Lactobacillus johnsonii is a key regulator of respiratory tract protection from negative environmental factors," Lynch noted. She believes that Lactobacillus johnsonii or other beneficial bacteria in the future can be used to purposefully change the composition of the intestinal microflora, allowing to prevent or even treat asthma and other allergic diseases. "Manipulation of the composition of the intestinal microflora is a promising new therapeutic strategy for both respiratory infections and allergic respiratory diseases," Lynch said. She, however, stressed that further research is required before the introduction of such a method into clinical practice.
It is worth noting that this is not the first evidence that has recently appeared in the scientific literature of the critical influence of the composition of bacteria inhabiting the gastrointestinal tract on the development of various diseases. In particular, we are talking about autism, rheumatoid arthritis and multiple sclerosis.
Portal "Eternal youth" http://vechnayamolodost.ru18.12.2013