Lack of dietary iron weakens immune response in the lungs

Researchers at Columbia University have found that a lack of dietary iron early in life can prevent immune cells in the lung from making a key protein that helps fight viral infections, even after iron levels are restored. 

The findings suggest that immunological memory formed when iron levels are low may not provide adequate protection against future exposures to the same viruses.

Iron deficiency, which disproportionally affects children, is one of the most common nutritional problems worldwide and has long been linked to increased risk of viral infection and more severe illness. Our study sheds new light on one of the reasons why."

Thomas Connors, assistant professor of pediatrics, Columbia University Vagelos College of Physicians and Surgeons

The researchers focused on memory T cells - immune cells that help the body respond to previously encountered pathogens. To isolate the effect of iron, mice were fed an iron-rich or iron-poor diet and were then infected with influenza.

The iron-deficient mice had more severe illness and showed impaired activation of T cells in the lung compared with mice on an iron-rich diet.

Mice with very low iron levels were able to form normal-looking memory T cells in the lung. But further testing revealed that the ability of these memory cells to make interferon gamma and tumor necrosis factor alpha - proteins that help immune cells recognize and fight infections - was impaired. The defect persisted even after iron levels were restored, suggesting that iron deficiency not only makes it harder to shake an infection, but could also have a lasting impact on how the immune system responds to future viral threats. 

Nearly 10% of children in the United States are iron deficient, making it one of the most common nutritional concerns in early life. Although routine screening for anemia - a late consequence of iron deficiency - helps identify children most in need of treatment, prevention remains essential. Because infancy and childhood are periods of rapid growth and development, including the maturation of the immune system, adequate iron intake during these years is especially critical.

"Our study underscores the importance of dietary iron for immune system development and future health," Connors says. "Making sure kids eat a well-balanced diet and get routine screening with their pediatrician is key."

Connors' team plans to study the immune system in children with iron deficiency to provide insights into how to boost immune response. The researchers will also study the effect of iron deficiency on lung tissue to better understand why low iron levels are associated with chronic lung conditions, such as asthma.