The Development of the Immune System in Babies: Vulnerabilities and Resilience against Respiratory Infections

2023-07-19 06:00:00

Researchers from the Irving Medical Center at Columbia University (USA) have recently highlighted the different aspects of the development of the immune system, which distinguishes babies from adults. In particular, they discovered why newborns are more prone to repeated episodes of respiratory infections such as bronchiolitis, but are less likely to contract new pathogens compared to adults.

Immature immune cells in infants

As part of this work, American scientists conducted two studies in which they analyzed tissue samples from deceased pediatric organ donors.

Published in the journal Immunity, the first study found that immune cells, called memory T cells, which form following first exposure to a pathogen, accumulate rapidly in the lungs and intestines until the age of three. These cells therefore participate in setting up an appropriate immune response in the event of contact with a virus or bacteria in older children and adults.

However, scientists have made an important discovery. “We found that memory T cells in young children are not functionally mature and only begin to have the ability to protect immunity around four to six years of age (…) This explains why babies and young children are more vulnerable to recurrent respiratory infections and other infectious diseases than adults,” said Donna Farber, study co-author and Professor of Surgical Sciences, Microbiology and immunology at the Irving Medical Center.

Resistance to new viruses: “this mechanism helps young children react to many respiratory pathogens”

In the second study published in the journal Nature ImmunologyHowever, the researchers found that babies have a kind of “protection” once morest new pathogens despite their susceptibility to common respiratory infections. According to the American team, groups of antibody-producing B cells surrounded by T cells are present in the lungs of infants. This lymphoid tissue forms between six and twelve months before gradually disappearing following three years.

“This allows the lungs to produce antibodies once morest respiratory pathogens long before T-cell memory develops, but these antibodies disappear in late childhood when they are no longer needed (…) This mechanism helps the young children to respond to the many respiratory pathogens they encounter early in life,” said Donna Farber. This physiological process might be why young children are more resistant to new respiratory infections like Covid-19.

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