In a recent research briefing published in Nature Medicine, researchers highlighted the importance of air quality in preserving immune health throughout the human lifespan, particularly lung-related immunity, due to exposure to continuous from the lungs to the environment.
Study: Effect of air pollution on the human immune system. Image credit: Lemberg Vector studio/Shutterstock
background
Aging exacerbates susceptibility to disease, a harsh reality that emerged during the unprecedented coronavirus disease 2019 (COVID-19) pandemic. However, the elderly are not only more prone to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, but are also prone to other lung diseases, for example, chronic obstructive pulmonary disease (COPD ) and lung cancers.
As people age, age-related changes in immune cells and subsequent systemic inflammation functionally impair their acquired immunity, likely increasing their susceptibility to disease. Because the immune system resides in mucosal and lymphoid tissues, the effect of increasing age on local immune responses in these regions needs detailed evaluation.
A better understanding of the physiological mechanisms that exacerbate disease susceptibility in the elderly could help reduce health care costs associated with disease in a rapidly aging global population. In particular, people in the age group of 60 years and above consume a large proportion of healthcare funds worldwide.
About the study
In the present study, the researchers obtained lymph node (LN) samples from human organ donors of different age groups to investigate the effect of the particles on their immune cells. Because they observed pronounced effects of air pollutants on LNs in the lungs compared with LNs in the gut, they used quantitative imaging to visualize LN architecture at all LN sites. In addition, they used functional and cellular assays to analyze the effect of aging on LNs.
Results of the study
The researchers observed an accumulation of black particles in lung-related LNs that increased substantially in samples from individuals over 40 years of age. In contrast, bowel-related LNs remained beige in color and lacked black particles.
Particles in lung-related LNs remained confined to a specific population of macrophages nested in the T-cell spread (not within follicles). These macrophage subsets showed functional alterations, including impaired cytokine secretion, reduced activation, and markedly reduced phagocytic potential. Interestingly, macrophages without particles lodged within the same LN did not show any functional alterations. Finally, the researchers also found that particle accumulation in lung-related LNs led to age-related changes in the structural integrity of LNs, due to alterations in lymphatic drainage and cell follicles. B cells.
Taken together, the study results demonstrated the direct and deleterious effects of inhaled particles on acquired and innate immune processes that build up over time in the lymphoid system responsible for immune surveillance of the respiratory system, especially the lungs.
When lung-related LNs become clogged with particles, their ability to filter toxins, dangerous antigens, and microbial pathogens is substantially diminished. Outcomes worsen with age, which to some extent rationalizes the increased risk of respiratory disease in the elderly compared to the younger population.
Conclusions
The current study provided new insights into how environmental pollutants interact and alter the human immune system by examining LN samples rather than blood samples from deceased organ donors of different age groups.
Future studies should explore the mechanisms that lung-related LN-specific macrophages use to contain particles. Studies should also investigate whether these macrophages are LN residents, derived from lung macrophages, or migrate to the lungs from other LN sites (eg, mucosal sites). Further research is also required to investigate the effects of particle accumulation on pathways other than the phagocytosis pathway in LNs that removes cellular debris and microbial pathogens.
In addition, the study should motivate further research exploring the effects of carbon emissions and other types of pollution on the human immune system.