HMN 2025: What is the placental inflammation as the cause of allergic diseases such as pediatric asthma

It is already well known that when a mother experiences inflammation during pregnancy, her child is more likely to develop allergic diseases. Recently, a KAIST research team became the first in the world to discover that inflammation within the placenta affects the fetus’s immune system, leading to the child exhibiting excessive allergic reactions after birth.

The study, published in the journal Mucosal Immunology, presents a new possibility for the early prediction and prevention of allergic diseases such as pediatric asthma.

The study led by Professor Heung-kyu Lee from the Department of Biological Sciences found that inflammation occurring during pregnancy affects the fetus’s stress response regulation system through the placenta.

As a result, the survival and memory differentiation of T cells (key cells in the adaptive immune system) increase, which can lead to stronger allergic reactions in the child after birth.

The research team proved this through experiments on mice that had excessive inflammation induced during pregnancy. First, they injected the toxin component “LPS (lipopolysaccharide),” a substance known to be a representative material that induces an inflammatory response in the immune system, into the mice to cause an inflammatory response in their bodies, which also caused inflammation in the placenta.

It was confirmed that the placental tissue, due to the inflammatory response, increased a signaling substance called Tumor Necrosis Factor-alpha (TNF-?), and this substance activated immune cells called neutrophils, causing inflammatory damage to the placenta.

This damage modulated the postnatal offspring stress response, leading to a large secretion of the stress hormone (glucocorticoid). As a result, the offspring’s T cells, which are responsible for immune memory, survived longer and had stronger memory functions.

In particular, the memory T cells created through this process caused excessive allergic reactions when repeatedly exposed to antigens after birth. Specifically, when house dust mite allergens were exposed to the airways of mice, a strong eosinophilic inflammatory response and excessive immune activation were observed, with an increase in immune cells important for allergy and asthma reactions.

Professor Heung Kyu Lee stated, “This study is the first in the world to identify how a mother’s inflammatory response during pregnancy affects the fetus’s allergic immune system through the placenta.”

He added, “This will be an important scientific basis for developing biomarkers for early prediction and establishing prevention strategies for pediatric allergic diseases.”