The diminished power of the immune system in older adults is usually blamed on the aging process. But a new study by Columbia immunologists shows that decades of particulate air pollution also take a toll.

The study found that inhaled particles from environmental pollutants accumulate over decades inside immune cells in lymph nodes associated with the lung, eventually weakening the cells’ ability to fight respiratory infections.

The findings—published Nov. 21 in Nature Medicine—offer a new reason why individuals become more susceptible to respiratory diseases with age.

>Older people are particularly susceptible to infectious and neoplastic diseases of the lung and it is unclear how lifelong exposure to environmental pollutants affects respiratory immune function. In an analysis of human lymph nodes (LNs) from 84 organ donors aged 11–93 years, we found a specific age-related decline in lung-associated, but not gut-associated, LN immune function linked to the accumulation of inhaled atmospheric particulate matter. Increasing densities of particulates were found in lung-associated LNs with age, but not in the corresponding gut-associated LNs. Particulates were specifically contained within CD68+CD169− macrophages, which exhibited decreased activation, phagocytic capacity, and altered cytokine production compared with non-particulate-containing macrophages. The structures of B cell follicles and lymphatic drainage were also disrupted in lung-associated LNs with particulates. Our results reveal that the cumulative effects of environmental exposure and age may compromise immune surveillance of the lung via direct effects on immune cell function and lymphoid architecture.