The fact that newborns are especially vulnerable to bacterial infections is not necessarily a sign of immaturity or even a bad thing; rather it could be understood as something positive. In experiments with mice carried out by paediatricians at the Cincinnati Children’s Hospital (USA), it has been discovered that a mice newborn’s body deliberately “deactivates” its immune system for a critical period of time. This happens to allow the invasion of beneficial bacteria that colonise the stomach, skin, mouth and lungs, leading to the leading to a greater diversity of our microbiota. The mechanism is a means of avoiding an excessive immune response on leaving the environment of the womb and coming into contact with different types of microbes. In other words, this period of “permissiveness” by the immune system may be essential for good health during the rest of the baby’s life, as previously explained on this blog.
Researchers, led by Dr. Sing Sing Way, observed how the blood of six-day-old rodents showed a large amount of red blood cells with a protein called CD71, much more than the amount present in the blood of an adult mouse. These cells seem to have a key function of temporarily suppressing the immune system’s defensive response by producing an enzyme called arginase. Through this, the body avoids a negative reaction when it first comes into contact with bacteria and fungi. In fact, the human umbilical cord also has more cells with CD71 than adult blood, according to the researchers’ findings presented in Nature.
If researchers confirm that the human body has a similar mechanism, the study may lead to practical applications including, for example, treating some newborn infections.