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Infant Immune Systems Are Stronger Than You Think

New study may help explain why infants are less affected by COVID than adults

December 10, 2021

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As any parent knows, infants are prone to getting respiratory infections.

But a new study shows that the infant immune system is stronger than most people think and beats adults at fighting off new pathogens.

The infant immune system has a reputation for being weak and underdeveloped when compared to the adult immune system, but the comparison isn’t quite fair, says Donna Farber, PhD, professor of microbiology & immunology and the George H. Humphreys II Professor of Surgical Sciences at Columbia University Vagelos College of Physicians and Surgeons.

Babies do get a lot of respiratory illnesses from viruses, like influenza and respiratory syncytial virus, compared to adults. But unlike adults, babies are seeing these viruses for the first time. “Adults don’t get sick as often because we’ve recorded memories of these viruse, and the memories protect us,” Farber says, “whereas everything the baby encounters is new to them.”

In the new study, Farber and colleagues leveled the playing field and only tested the immune system’s ability to respond to a new pathogen, essentially eliminating any contribution from immunological memories.

For the head-to-head comparison, the researchers collected naïve T cells—immune cells that have never encountered a pathogen—from both infant and adult mice. The cells were placed into an adult mouse infected with a virus.

In the competition to eradicate the virus, the infant T cells won handily: Naïve T cells from infant mice detect lower levels of the virus than adult cells and the infant cells proliferated faster and traveled in greater numbers to the site of infection, rapidly building a strong defense against the virus. A laboratory comparison found similar enhancements among human infant compared to adult T cells.

“We were looking at naïve T cells that have never been activated, so it was a surprise that they behaved differently based on age,” Farber says. “What this is saying is that the infant’s immune system is robust, it's efficient, and it can get rid of pathogens in early life. In some ways, it may be even better than the adult immune system, since it’s designed to respond to a multitude of new pathogens. ”

That appears to be playing out in the case of COVID. “SARS-CoV-2 is new to absolutely everybody, so we’re now seeing a natural, side-by-side comparison of the adult and infant immune system,” Farber says. “And the kids are doing much better. Adults faced with a novel pathogen are slower to react. That gives the virus a chance to replicate more, and that’s when you get sick.”

The findings also help explain why vaccines are particularly effective in childhood, when T cells are very robust. “That is the time to get vaccines and you shouldn't worry about getting multiple vaccines in that window,” Farber says. “Any child living in the world, particularly before we started wearing masks, is exposed to a huge number of new antigens every day. They’re already handling multiple exposures.”

The study could lead to better vaccine designs for children.

“Most vaccine formulations and doses are the same for all ages, but understanding the distinct immune responses in childhood suggests we can use lower doses for children and could help us design vaccines that are more effective for this age group,” Farber says.

References

More information

The paper, titled "Infant T cells are developmentally adapted for robust lung immune responses through enhanced T cell receptor signaling," was published Dec. 10 in Science Immunology.

Donna Farber also is chief of the Division of Surgical Sciences in the Department of Surgery, Columbia University Vagelos College of Physicians and Surgeons, and principal investigator at the Columbia Center for Translational Immunology.

All authors (all from Columbia University unless noted): Puspa Thapa, Rebecca S. Guyer, Alexander Y. Yang, Christopher A. Parks, Todd M. Brusko (University of Florida), Maigan Brusko (University of Florida), Thomas J. Connors, and Donna L. Farber.

This work was supported by the U.S. National Institutes of Health (NIH grants AI100119, AI106697, K23 AI141686, and AI42288) and the Helmsley Charitable Trust. Studies were performed in the Columbia Center for Translational Immunology’s Flow Cytometry Core, supported by NIH grants S10RR027050 and S10OD020056, and the Columbia Stem Cell Initiative’s Flow Core, supported in part by NIH grant S10OD026845.

The authors declared no competing interests.

Immunity in newborns | When it appears and what factors affect it

The main principle of maintaining a child's health is to avoid extremes. It is impossible to protect him from any threat, but insufficient attention to the well-being of the baby will also be wrong. To better understand how the defense mechanism works in young children, let's understand the basic concepts.

What is immunity?

Like adults, immunity in newborns is a complex system whose task is to protect the body from pathogens. Two components are involved in this difficult struggle - cellular and humoral immunity.

Protective cells are able to recognize the "enemy", overcome it and at the same time remember how to deal with this particular microbe. Thus, the immune memory of the body is formed, thanks to which we get sick much less often.

When does a newborn become immune?

At the time of the birth of a baby, his body encounters a million unfamiliar microorganisms. So that the reaction is not too violent and does not harm the child, nature provides a system of factors that inhibit the immune response.

In the first months of life, the immunity of newborns is borrowed from the mother. Basically, special immunoglobulins are responsible for protecting the newborn. They enter the body during pregnancy, in the third trimester. That is why premature babies get sick more often and adapt worse to a new environment.

Gradually, the protective cells of the mother are replaced by their own, and by 11–12 months the body begins to provide a protective function on its own.

What factors affect the immunity of a newborn baby

Breastfeeding plays an important role in the formation of immunity. Young children are very susceptible to intestinal infections, and the immune cells that come with mother's milk provide reliable protection.

Important!

The World Health Organization recommends breastfeeding to strengthen the immune system of the newborn. It must be continued for at least a year, and preferably up to two years.

The immunity of a newborn child directly depends on the conditions in which he lives. A stuffy, dusty room with dry air contributes to the drying of the nasal mucosa. As a result, the baby loses the ability to defeat viruses before they enter the body. On the contrary, regular airing, humid cool indoor air and frequent walks are a great way to strengthen the immunity of a newborn.

How to strengthen the immune system of a newborn?

If a child starts to get sick often, parents worry and look for an answer to the question: how to improve the immunity of a newborn?

Don't diagnose your child yourself. If you suspect any disorders in your child, contact a specialist. He will determine the cause of the condition and recommend how to raise the immunity of a newborn child.

Important!

Do not self-medicate! In no case should you give your child immunomodulatory drugs unless they are prescribed by a specialist.

A newborn baby's immune system can be weakened for many reasons. Serious violations of the protective system are quite rare, occurring in one case out of several thousand. Such situations require the attention of narrow specialists. The district pediatrician will give a referral to them.

Ways to strengthen immunity

Simple rules will help strengthen the immunity of a newborn:

• choose breastfeeding if possible;
• walk more;
• observe the rules of hygiene and cleanliness;
• Use medicines only as prescribed by a specialist.

These simple tips help keep your child healthy and developing. Experts are unanimous in their opinion that over the centuries the human defense system has become strong enough to withstand the attacks of viruses and microorganisms. Nature itself gives the baby everything possible to protect him from any threat.

⚕ Do newborns have immunity?👼

When a baby is born, parents immediately worry about his health. One of the most common questions of young mothers and fathers is “Does a newborn have immunity?” It is answered by the pediatricians of the Pulse family clinic.

• Immune system is a system of organs and structures that is responsible for protecting the body from foreign factors - bacteria, viruses, etc.;
• Immunity is the actual reaction of the immune system, that is, the response to stimuli.

The immune system itself is formed in the child in the womb of the mother. But immunity develops during the first years of life. This is because the baby's immune system has not yet been trained in all the subtleties.

Features of the immunity of newborns

• During 9 months of pregnancy, a large number of immunosuppressants are present in the blood of an infant. These cells specifically weaken the child's own immunity so that its development does not conflict with the mother's body.
• Immediately after birth, a sterile baby faces the outside world. Passive protection in the first 29 days of life is given to him by IgG immunoglobulins, which he received from his mother. These are antibodies against all pathogens that the mother has encountered. In the course of life, the amount of maternal antibodies in the baby's body decreases, and completely disappears by the 6th month.
• If a mother feeds a child with her own milk, then she gives him additional protection - IgA. They protect the mucous membranes from external attack by microorganisms. This applies to the nasopharynx, intestines, eyes and the like.
• Gradually, the baby's body adapts to the new world and forms its own immune response, producing its own cells of the immune system. A smooth transition occurs in the first year of life.

There are three critical periods for the formation of immunity

• The first month. During this period, the cells of the immune system are learning, so the baby's body is very vulnerable. It is protected only by maternal antibodies;
• 6 months. In six months, almost all maternal antibodies disappear, and the baby begins to get sick;
• 2 years. At this time, the baby actively gets acquainted with the world, goes to children's groups. Immunity trains, SARS and a runny nose occur.

The final immune protection in a child will be formed only in adolescence - at 15 years old, and work all his life.

We remind you that the best way to train the immune system and protect against dangerous diseases is vaccination.

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