Ambient particulate matter (PM), a major component of air pollution, aggravates ocular discomfort and
inflammation, similarly to
dry eye disease (DED) or
allergies. However, the mechanism(s) by which PM induces the ocular inflammatory response is unknown. This study investigated the immunological response of traffic-related fine
particulate matter (PM2.5) on the ocular surface in a murine model. C57BL/6 mice were exposed by topical application to PM2.5 or vehicle for 14 days to induce experimental environmental ocular disease. Corneal
fluorescein staining and the number of ocular inflammatory cells were assessed in both groups. The expression of IL-1β,
IL-6,
tumor necrosis factor (TNF)-α, and
mucin 5AC (MUC5AC) in the ocular surface were evaluated by real-time PCR. An immunohistochemical assay evaluated apoptosis and goblet cell density. ELISA was used to determine the levels of serum
IgE and
cytokines of Type 1 helper (Th1) and Type 2 helper (Th2) cells after in vitro stimulation of T cells in the draining lymph nodes (LNs). Exposure to traffic-related PM2.5 significantly increased corneal
fluorescein staining and cellular toxicity in the corneal epithelium compared with the vehicle control. A significant increase in the number of CD11b+ cells on the central cornea and mast cells in the conjunctiva was observed in the PM2.5 group. Exposure to PM2.5 was associated with a significant increase in the corneal or conjunctival expression of IL-1β,
IL-6, TNF, and MUC5AC compared to the vehicle, and increased maturation of dendric cells (DCs) (MHC-IIhighCD11c+) in draining LNs. In addition, PM2.5 exposure increased the level of serum
IgE and Th2
cytokine production in draining LNs on day 14. In conclusion, exposure to traffic-related PM2.5 caused ocular surface damage and
inflammation, which induced DC maturation and the Th2-cell-dominant allergic immune response in draining LNs.