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Lung immunity can decline with age, making older adults more susceptible to lung damage and serious respiratory infections. New research shows one reason why this might be so: Particulate matter inhaled from pollution acts over time to weaken the lungs’ immune system, researchers report online Nov. 21 in Nature Medicine.
Air pollution is a leading cause of disease and premature death worldwide, disproportionately affecting the poor and marginalized (SN: 30/7/20). Particulate matter – a type of pollution emanating from vehicle exhaust, power plants, wildfires and other sources – has been linked to health hazards including respiratory, cardiovascular and nervous diseases (SN: 09/19/17).
In the new study, Columbia University researchers analyzed lung immune tissue from 84 organ donors aged 11 to 93 years. The donor is not a smoker or has not smoked heavily in the past. As we age, the lungs’ lymph nodes – which filter foreign matter and contain immune cells – become loaded with particles, turning them into deep onyx, the research team found.
“When [lymph nodes] are filled with that much stuff, they can’t do their job,” said Elizabeth Kovacs, a cell biologist who studies inflammation and injury at the University of Colorado’s Anschutz Medical College in Aurora.
Lymph nodes house a variety of immune cells, including macrophages. This mobile Pac-Man devours pathogens and other debris, including particles. Filled with pollutants, the production of macrophage cytokines, proteins that cells secrete to activate other immune cells, decreases. The cells also showed signs of a reduced ability to gobble up more.
The new study suggests that older people have accumulated so much waste “that they may not be able to collect more,” affecting their ability to deal with inhaled material, said Kovacs, who is not involved with the study was.
Pollution “is an ongoing and growing threat to the health and livelihoods of the world’s population,” the research team wrote. Their work found that threats involve “chronic and pervasive effects” on respiratory immunity as people age.
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