Biological effects of airborne fine particulate matter (PM2.5) exposure on pulmonary immune system

Airborne fine particulate matter (PM2.5) attracts more and more attention due to its environmental effects. The immune system appears to be a most sensitive target organ for the environmental pollutants. Inhaled PM2.5 can deposit in different compartments in the respiratory tract and interact with epithelial cells and resident immune cells. Exposed to PM2.5 can induce local or systematic inflammatory responses. This review focus on the effects of respiratory tract exposed to PM2.5. Firstly, we introduced the major emission sources, basic characteristics of PM2.5 and discussed its immunoadjuvant potential. Secondly, we elaborated the immune cells in the respiratory tract and the deposition of PM2.5 regarding the structural characteristics of the respiratory tract. Furthermore, we summarized the in vivo/vitro studies that revealed the immunotoxic effects of PM2.5 exposure to pulmonary cellular effectors and explored the contribution of PM2.5 exposure to the Th1/Th2 balance.