pets and children's

pets and children's acquisition of immunity 

For some of us, interaction with animals was the order of the day in childhood, while for others, the long-awaited gift barking under the Christmas tree - never came. However, no one would have thought back then that a ball of fur would have multiple benefits, in addition to recreational ones.

The immune system - general concepts

Most of us know a definition of what the immune system means. In familiar terms, it is that system that protects our body from pathogens, toxins, and, implicitly, diseases and infections. It also helps us fight them once contracted. In scientific terms, however, the immune system has a broader explanation – an assembly of cells, lymphoid organs, and molecules with a protective role, which contributes to two types of responses:

● Natural or innate response – cellular and molecular mediated (eg phagocytosis of invading pathogens, lysozyme from saliva and tears, which destroys microbes, etc.). We are born with this type of response that is not specific, acting on any germ.

● Adaptive or acquired response - occurs after prolonged or repeated exposure to a particular disease, or infection, differing from the natural one by the production of antibodies - with specificity, for example, antibodies formed against the antigens of COVID-19 will attach to them in a subsequent illness, easing or even eradicating the symptoms of the disease.

Day by day we are invariably exposed to organisms that we can inhale, swallow, and come into contact with through the skin or mucous membranes. The disease is determined by the pathogenicity (capacity for virulence) of these organisms and the integrity of the host's defense systems.

Therefore, the under activity of the immune system can lead to the worsening of infections, the transition from acute to chronic, immunodeficiency, tumors, etc. In some cases, under activity leads, later, to an overactivity observed through the predisposition to allergies or autoimmune diseases.

Cell types

The cells involved in defense processes are popularly known as "white blood cells" - leukocytes, being universally known to "eat" microbes in the process called phagocytosis. This is, however, a summary of knowledge on the subject, leukocytes being a class composed of several types of cells:

● Neutrophils – the first elements that reach the tissue invaded by microbes and contribute to the formation of pus;

● Eosinophils – contain substances with an antihistaminic effect, being found especially in allergies, skin diseases, and parasitosis, conditions involving inflammation of various tissues;

● Basophils – more numerous in viral diseases (smallpox, chicken pox);

● Monocytes – common in bacterial infections, transform into macrophages and clear infections of pus (phagocytose dead neutrophils);

● Lymphocytes - particularly important due to their dual role in both cell-mediated defense, through "killer" T cells, and humoral-mediated defense, through the production of antibodies by B cells. These antibodies have the role of coupling with the antigens intruding into the body and stopping their effect.

The increased number of lymphocytes is a physiological (normal) state in children, whose immune system is developing.

Development of immunity in children

Exposure to germs during childhood is known to help develop the immune system and thus protect against allergies, asthma, and other conditions in adulthood.

In a study published in the journal Science, researchers demonstrate the effects of exposing mice to microbes at a young age, namely keeping the total number of T ("killer") lymphocytes low. These lymphocytes are important in the fight against infections, on the one hand, but in too large a number they can end up attacking the body of which they are a part, causing several ailments including those mentioned above.

Insufficient exposure to pathogenic organisms, spending time in mostly sterile environments, and early exposure to antibiotics have the effect of keeping too many T lymphocytes, which can, over time, cause problems in your own body. So, children's immune systems mature best when they are exposed to germs in the right amount. Too many germs are unhealthy, but so is a sterile home.

Also, the study shows that the lack of exposure to pathogens in youth cannot be compensated for in adult life, not having the same effect.

Contribution of pets

The appearance of a child is accompanied by many questions from parents, especially when a family member from another species is also present. One of the most common questions for families with pets is whether they will support the newborn in any way or have the potential to do more harm. The answer is almost always the former, especially when the animal in question is a dog. The potential benefits are as follows:

● Reducing the risk of developing allergies.

In two studies, one conducted by the American College of Allergy, Asthma and Immunology (2020) and the other in 2019 by a team of researchers, several links were found between owning a pet and a reduced risk of allergies.

An important finding of the first study is related to the low level of IgE (immunoglobulin E) in children with prenatal and postnatal exposure to animals - especially dogs.

This immunoglobulin is an antibody synthesized by our immune system, which contributes to the occurrence of allergic reactions by binding to allergens. Therefore, a high number of IgE is related to the hypersensitivity of people to different allergens and can be associated with the development of certain conditions such as asthma, eczema, and food allergies. In short, children who own pets have a reduced risk of developing allergies or autoimmune diseases.

Regarding food, the second mentioned study supports the fact that those children who live with a dog are 90% less susceptible to their development.

These ideas would be argued by the fact that pets have the disposition to bring into the owner's home the bacteria with which they came into contact outside, contributing to the diversification of the child's microbiome.

● Exposure to beneficial and pathogenic bacteria

Another 2017 study on the microbiome claims that pregnant women who lived with a dog or cat during pregnancy had increased levels of Oscillospira and Ruminococcus bacteria, which correlated with lower chances of allergies and obesity. It can be argued, therefore, that pets expose children not only to pathogens but also to beneficial bacteria.

On the other hand, pets, especially those that have a relationship with the outside, come into contact with bacteria, viruses, toxins, and organisms containing antigens, which they bring into the home, contributing to the exposure of children and thus stimulating the production varied by antibodies.

However, proper care of the animal's health, including a full vaccination and deworming schedule and normal hygiene, should be considered to avoid potential zoonoses.

● Decrease in stress level

All pet owners can probably relate to the feeling of relaxation after spending time with them, and this is true for people of all ages. Petting an animal was shown to be associated with a high level of relaxation and an increase in the amount of IgA in saliva, in a study by researchers Carl J. Charnetski and Sandra Riggers. IgA (immunoglobulin A) is the most abundant type of antibody found in the human body and plays an essential role in immune responses in mucosal surfaces such as oral, gastrointestinal, respiratory, and vaginal.

55 students divided into three groups took part in the study: group 1 petted a live dog, group 2 – a stuffed animal, and group 3 simply sat on the couch. Saliva samples showed a significant increase in this immunoglobulin only in group 1, which stroked a live animal.

Decreased levels of pet stress were also associated with lower blood pressure in stressful situations, increased levels of serotonin and dopamine, and decreased levels of circulating triglycerides and cholesterol.