In a new study, researchers found differences in lung physiology and immune function in children could be why they are more often spared from severe illness associated with COVID-19 than adults.
The research was conducted by a team at The University of Texas Health Science Center at Houston (UTHealth) and Baylor College of Medicine.
According to the team, only about 1.7% of the first 149,082 cases in the U.S. were infants, children, and adolescents younger than 18 years old.
They noted that children under 18 make up 22% of the U.S. population. Only three pediatric deaths were identified by the Centers for Disease Control and Prevention (CDC) as of April 2020.
Angiotensin-converting enzyme 2s, called ACE2, are the doors that allow SARS-CoV-2, the novel coronavirus that causes COVID-19, to enter the body’s cells. Children naturally have less ACE2 in the lungs than adults.
In addition to fewer ACE2 receptors, the authors note the immune system in children responds to viruses differently than that of adults, leaving less opportunity for severe illness in pediatric patients.
There are several different mechanisms behind the differences, including the retention of T-cells in children, which are able to fight off or limit inflammation.
Lung tissue in children naturally has a higher concentration of regulator T-cells.
Patients with higher levels of T-cells also have higher levels of Interleukin 10 (IL-10), also known as human cytokine synthesis inhibitory factor, an anti-inflammatory cytokine.
The team has begun a new study using blood samples from patients in different stages of COVID-19 to continue to understand how to treat the virus and the disparities in disease progression between children and adults.
One author of the study is Matthew Harting, MD, MS, an assistant professor in the Department of Pediatric Surgery.
The study is published in the American Journal of Physiology-Lung Cellular and Molecular Physiology.
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