Air pollution particles appear to weaken lung’s immune defenses over time

Older man with face mask covering nose and mouth stands in front of background that appears to be hazy due to air pollution.

Inhaled particles from air pollution accumulate in lung-associated lymph nodes and weaken immune defenses over time, according to an NHLBI-funded study published in Nature Medicine. The findings may help explain why older people are more susceptible to respiratory infections, such as influenza and COVID-19, the researchers said. 

In the study, researchers studied 84 deceased organ donors, ranging in age from 11 to 93 years old, to study immune cells in multiple mucosal and lymphoid tissues. They found that lung-associated lymph nodes collected from younger donors were largely beige, while those collected from donors over age 30 were blackened and got darker with increasing age. The researchers found that the blackened lymph nodes of these older donors were clogged with particles from airborne pollutants.  

Upon closer examination, the researchers also found that the pollutant particles in the lung’s lymph nodes were located inside macrophages, immune cells that normally destroy pathogens and other dangerous substances. The airborne particles appeared to impair the immune function of the macrophages of the older donors, weakening the lung’s defenses, the researchers said.  

“This is an interesting study that suggests air pollution may contribute to why older people become more susceptible to respiratory infections,” said James P. Kiley, Ph.D., director of the NHLBI’s Division of Lung Diseases. “In addition to supporting ongoing efforts to control air pollution, these findings underscore the importance of additional research to better understand the lung effects of inhaled particulates and the interactions between air pollution and chronic lung diseases.” 

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