We were born for a reason

Babies are born with a depressed immune system

20.07.2017

A low flame mode allows newborns to slowly get used to the outside world. This is described in a publication by the Hannover Medical School (MHH) and the Universities of Bonn and Münster in "Nature Immunology".

The immune system of infants appears to be deliberately on the back burner in the first year after birth. This is shown by a study by the Hannover Medical School (MHH) and the Universities of Bonn and Münster. In this way, nature presumably prevents the immune system from reacting too strongly to bacteria and foreign substances outside the womb after the birth. The results could also enable new therapeutic approaches to protect infants from so-called sepsis. This is a life-threatening inflammatory reaction that is particularly common in premature babies. The work has been published in the renowned journal "Nature Immunology".

It has long been known that the immune cells of newborns trigger inflammation only to a very small extent. Up until now, it was thought that the immune system in infants was not yet fully developed and therefore not particularly powerful. The results of the new study cast doubts on this interpretation: "We suspect that this reduced inflammatory response is based on a specific and meaningful programming," explained Dr. Thomas Ulas from the LIMES Institute at the University of Bonn.
As soon as the newborn leaves the womb, it suddenly comes into contact with countless unknown bacteria and foreign substances. "The" savings program "presumably prevents the body's own defense forces from getting involved in countless skirmishes," said Dr. Sabine Pirr from the Hannover Medical School (MHH). Otherwise, the result could be a life-threatening strong inflammatory reaction, sepsis. In addition, many of the unknown microorganisms are not pathogens at all. The intestine only functions as it should if it has been colonized with certain bacteria. For this reason, too, the immune system has to hold back.

Immune system with the handbrake on

The study shows how the immune system initially works with the handbrake on in the months after birth. This is gradually resolved until the young child's own defenses reach their full potential after about a year. "We took blood samples from newborns at different times and analyzed the programming of the immune cells," says the head of the study, Professor Dr. Dorothee Viemann from the Clinic for Pediatric Pneumology, Allergology and Neonatology at the Hannover Medical School.

This work was supplemented by a so-called transcriptome analysis. It examines which areas of the genetic construction instructions are read at a certain point in time. In view of the approximately 20,000 genes that each person carries around in their DNA, the evaluation is left to special computer programs. Dr. Thomas Ulas is a bio-computer scientist; he directed this part of the study. Other aspects of the child's immune system were examined at the “Cells in Motion” cluster of excellence at the University of Münster.

All in all, the result is an extremely detailed insight into the regulation of the body's own defense system: Normally, certain substances, for example in the shell of bacteria, trigger inflammation by activating a certain genetic program. However, newborns produce substances that prevent this - the S100-Alarmine. These are released from the time of birth.

In the course of the first few weeks of life, fewer and fewer of these S100 alarms are produced. At the same time, other mechanisms are activated that can regulate the immune system instead of the alarmins. "These programs are still largely inactive in newborns," explains Professor Viemann. "Children who do not generate enough alarms after birth do not have the handbrake, which is why they have a massively increased risk of serious infections."

Premature babies are particularly often affected by such sepsis, as the necessary Alarmin quantity is often only reached at the normal time of birth. The administration of S100 alarms can therefore prevent severe courses of sepsis. This approach has already shown great promise in experiments with mice.
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(Stefan Zorn, Press and Public Relations, Hannover Medical School)
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Source: idw, Hannover Medical School, Nature Immunology