Fakta om bebis immunförsvar, om antikroppar och amning. Direkt av professor i klinisk immunologi och mikrobiologi. Har nyfödda bebisar ett fungerande immunsystem eller inte? Vad gör antikropparna i bröstmjölken för nytta? Agnes Wold är professor i klinisk immunologi och mikrobiologi och en av Sveriges främsta experter på små barns immunförsvar och amningsimmunologi.
A healthy newborn has a functioning immune system
The newborn baby is born with a fully functioning immune system. It has full capacity to form immune responses to virtually all types of infections (except: enclosed bacteria). BUT since the child has had no infections, it lacks immunological memory. When you first encounter a virus you become ill. At the same time, the immune system is activated and after the infection has passed, the immune system remembers exactly how this virus looks. If you encounter this virus again, you will not be able to get sick before the immune system is activated and the virus is eliminated.
The immunological memory
Now, unfortunately, there are hundreds of different viruses and if you have not encountered a particular virus you also have no immunological memory, and become ill. Since the child is born without immunological memory, it must simply go through all the viral diseases, to develop its immunity. If there is no vaccine. It is the simple explanation as to why toddlers "are sick always" - preschool children have on average 6-8 viral infections per year), whereas we "only" have 2-4 per year in an adult. The good news is that if you have many infections that small, for example because you are in kindergarten, you get fewer infections when you start school. All because of the immunological memory!
Mothers give children antibody protection!
To compensate the newborn for the lack of immunological memory, antibodies are given by the mother during pregnancy. IgG antibodies are actively pumped through the placenta to the baby, which is therefore born with higher IgG levels in the blood than the mother has! These break down gradually, as the child begins to form its own IgG antibodies.
Calves and pigs, for example, lack this excellent system and are born without these antibodies. They die if they do not receive breast milk immediately after birth, because there is IgG that is taken up in the blood.
Breast milk gives the child IgA antibodies which provide extra infection protection
Man is born fully-pumped with antibodies. As additional protection, the newborn receives large amounts of pre-produced IgA antibodies via breast milk. This IgA is not taken up but is kept on the mucous membranes where they prevent bacteria and viruses from entering the body. Therefore, breastfeeding protects against infections, especially sepsis (“blood poisoning”, ie bacteria in the blood) and bacterial diarrheal diseases. This is vital in poor countries, but in Sweden, blood poisoning is uncommon in healthy full-term infants and we can usually treat it with antibiotics. In principle, no infants in Sweden become ill from bacterial diarrheal diseases (Salmonella, Shigella and others). The bacterial infections that are most common in Sweden are ear infections, where breastfeeding provides some protection.
IgA antibodies protect the immune system from viruses and bacteria
While IgA in the breast milk protects against infections from viruses and bacteria, they also prevent them from coming into contact with the child's immune system and thus delay the build-up of an immunological memory. Nature prioritizes the child to grow up to be better equipped when the infections strike. They do this as soon as breastfeeding ends. Then the child has to make his own antibodies. In countries with a lot of infections and lack of clean water, this is a dangerous time when children are often suffering from severe diarrhea, so-called “weaning diarrhea”. Weaning diarrhea does not exist in a country of high hygiene standards such as Sweden. The fact that the child has received IgG from the mother (via the placenta) and IgA (via the breast milk) does not speed up the child's own production, on the contrary.
Breastfeeding offers important diarrhea protection when the water is infected
WHO recommends exclusive breastfeeding (full lactation) for four to six months. The reason is to reduce the risk of infections and malnutrition in poor countries with high infant mortality and lack of clean water and safe food. The main reason for this is that the water, the bottles and the formula there are infested with bacteria, often dangerous ones. In addition, children are often malnourished by formula feeding in poor countries with poor hygiene, both because of diarrhea and because mothers cannot afford to buy enough replacement powder and dilute it too much.
In Sweden, where we have clean water and safe food, there are really no strong medical reasons for exclusive breastfeeding (full lactation). Replacement mixed according to the instructions on the package is good enough for the child here, although it does not contain IgA antibodies at all. Just so you know, since olden times you have probably chewed food and put it in the child's mouth. Many studies show that children in all countries and at all times received tasting portions of one thing or the other in parallel with breastfeeding.