Particulate Matter and Innate Airway Immunity: Mechanisms of Disruption and Impact on Respiratory Infections.

BACKGROUND: Air pollution is a major global public health challenge, with particulate matter (PM) as a leading environmental risk factor for increased morbidity and premature mortality worldwide. The respiratory tract is the primary interface for PM exposure, where airway epithelial cells and innate immune systems coordinate frontline host defense. Chronic PM-exposure disrupts this system, impairing airway immune homeostasis and increasing susceptibility to respiratory infections.

OBJECTIVE: This review aims to integrate current molecular and cellular evidence describing how PM affects airway innate immunity, focusing on its impact on host defense mechanisms and its role in increasing susceptibility to respiratory infections.

METHODS: A comprehensive literature review was conducted focusing on PM interactions with the respiratory tract and their effects on airway epithelial and innate immune functions, emphasizing mechanisms of immune dysregulation.

RESULTS: PM-exposure induces innate immune dysregulation characterized by oxidative imbalance, altered cytokine and chemokine signaling, reduced phagocytic capacity, and decreased production of host defense peptides, resulting in impaired epithelial barrier integrity, persistent inflammation, defective pathogen clearance, and increased susceptibility and severity of respiratory infections, including tuberculosis, bacterial pneumonia, and viral respiratory diseases such as COVID-19.

CONCLUSION: PM is a key driver of airway innate immune dysfunction and increased susceptibility to respiratory infections by disrupting epithelial and immune defense pathways, weakening host resistance, and exacerbating disease burden. Further studies are needed to elucidate PM-immune interactions and support the development of preventive and therapeutic strategies.