ABSTRACT
This study was conducted to determine whether exposure to particulate matter 2.5 (PM2.5) affects the immune tolerance ofneonatal mice via the regulation of PD-L1 expression. One-week-old BALB/c mice were exposed to PM2.5 for 8 days.From day 8 to day 18, the mice were treated with 5 lg house dust mite (HDM) (i. n.) every two days. Adenovirus-carriedPD-L1 overexpression vectors were infected into mice via nasal inhalation 6 days after exposure to PM2.5. Airway hyperresponsiveness (AHR) was examined in mice 19 days after exposure to PM2.5, and the related parameters of airwayinflammation were studied on day 22. Co-exposure to PM2.5 and HDM reduced PD-L1 expression but greatly increasedinfiltration of inflammatory cells, which was reversed by PD-L1 overexpression. Co-exposure to PM2.5 and HDM alsoelevated serum IL-4, IL-5 and IL-13 levels and reduced TGF-b level. Exposure to PM2.5 alone slightly increased thenumbers of dendritic cells (DCs) but reduced the numbers of antigen-presenting cells expressing PD-L1 and Treg cells.Therefore, early exposure to PM2.5 reduced PD-L1 expression in the lungs of neonatal mice, which interfered with immunetolerance establishment and subsequently resulted in allergic airway inflammation