Children's immune system: It is much stronger than often thought

Created: 01/02/2022, 3:00 PM

From: Jennifer Köllen

Small children are often sick.

But that is not because your immune system is not good, on the contrary: It is in top shape and working at full speed.

New York - toddlers are constantly sniffed and bring home every infection in the area.

Nevertheless, their immune system is by no means weaker than that of adults, report researchers in the specialist journal "Science Immunology" after experiments with young mice and human cells.

In particular, the T cells of the immune system reacted quickly and effectively when they came into contact with a previously unknown virus.

This may explain - among other factors - the often milder course of corona infections in children.

Children's immune system: It is much stronger than often thought

The child's immune system has a reputation for being weak and underdeveloped, says study director Donna Farber of Columbia University Medical Irving Center in New York.

But that is not true, even if babies and toddlers often suffer from viral respiratory infections, caused for example by the RSV virus (respiratory syncytial virus).

That is solely because babies encountered these viruses for the first time.

"Adults don't get sick that often because we have memories of these viruses that protect us," says Farber.

"For babies, however, everything they encounter is new."

The immune system of children usually reacts faster and more effectively to new pathogens than that of adults.

(Symbol picture) © Annette Riedl / dpa

In order to examine the capabilities of the child's immune system more closely, the researchers collected immune system T cells from young and adult mice.

These included cells that had not previously come into contact with a pathogen, so-called naive T cells.

T cells are specialized defense cells.

There are different types of them, for example some can recognize virus-infected cells and kill them, while others store memories of individual pathogens in order to be able to initiate defense measures more quickly in the event of a renewed infection.

The researchers then administered these T cells to mice, which they then infected with an influenza virus, the causative agent of the flu.

Children's immune system: Naive T cells multiply faster

The naive T cells of young mice reacted to much smaller amounts of the virus than those of adults. They multiplied faster and migrated in greater numbers to the lungs, where influenza viruses mainly multiply. For the researchers it was surprising that the cells reacted differently depending on age. "This means that the toddler's immune system is robust and efficient and can eliminate pathogens at an early age," says Farber. "In some ways, it may even be better than an adult's immune system because it is designed to respond to a wide variety of new pathogens."

“Early childhood is the time when a particularly large number of T cells are formed in the thymus,” explains Marcus Peters, head of the lung immunology group at the Ruhr University in Bochum.

“With increasing age, fewer and fewer T cells are formed, which means that the ability to react to new things also decreases.” Even adults would still have a reservoir of naive T cells, but a smaller one.

For this purpose, older people have a standard reservoir of memory T cells that has grown over the course of their lives, which are tailored for the immune response to certain pathogens.

If they come into contact again with known pathogens, their immune system can react quickly.

Children's immune system: Children do better with Sars-CoV-2

The child's ability to quickly find an answer to new dangers may pay off in the case of Sars-CoV-2.

The virus is new to everyone, so you are currently experiencing a direct comparison between the child's and the adult's immune system.

“And the kids do better.” Older adults confronted with a new virus reacted more slowly.

This gives the virus more time to multiply, and you get sick.

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Immunologist Peters explains that children, despite their very active and powerful immune system, often suffer from mostly harmless infections more often than adults than adults.

“That then goes hand in hand with symptoms of the disease.” However, fever or swollen nasal mucous membranes did not indicate a failure of the immune system, on the contrary, that it was working well.

Immune system of children: Do not overwhelm the immune system with vaccinations

Their work also gives clues as to why vaccinations are particularly effective in childhood, the researchers around Farber continue to write. You shouldn't worry about getting multiple vaccinations during this time. "Every child who lives in the world, especially before we started wearing masks, is exposed to a large number of new antigens every day." Their immune system is used to dealing with them.

“The antigens in the vaccines that trigger an immune response only ever activate the T cells that exactly match them. T cells that react to the coronavirus, for example, do not react to pneumococci. "The immune system is therefore not overwhelmed by vaccinations, says immunologist Peters. In general, the immune system is constantly active and is constantly dealing with antigens that enter the body from the environment, both harmless and disease-causing.

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