Purpose: To investigate the ocular immune response following exposure to airborne titanium dioxide (TiO 2) microparticles.

Methods: Rats in the TiO 2-exposed group (n= 10) were exposed to TiO 2 particles for 2 hours twice daily for 5 days, while the controls (n= 10) were not. Corneal staining score and tear lactic dehydrogenase (LDH) activity were measured to evaluate ocular surface damage, serum immunoglobulin (Ig) G and E were assayed by using enzyme-linked immunosorbent assay, and the size of cervical lymph nodes was measured. In addition, the expression of interleukin (IL)-4, IL-17, and interferon (IFN)-γ in the anterior segment of the eyeball and cervical lymph nodes was measured by immunohistochemistry, real-time reverse transcription-polymerase chain reaction (RT-PCR), and Western blot analysis.

Results: Median corneal staining score (3.0), tear LDH activity (0.24 optical density [OD]), and cervical lymph node size (36.9 mm 2) were significantly higher in the TiO 2-exposed group than in the control group (1.0, 0.13 OD, and 26.7 mm 2, respectively). Serum IgG and IgE levels were found to be significantly elevated in the TiO 2-exposed group (P= 0.021 and P= 0.021, respectively). Interleukin 4 expression was increased in the anterior segment of the eyeball and lymph nodes following TiO 2 exposure, as measured by immunostaining, real-time RT-PCR, and Western blot. In addition, IL-17 and IFN-γ levels were also increased following TiO 2 exposure compared to controls as measured by immunostaining.

Conclusions: Exposure to airborne TiO 2 induced ocular surface damage. The Type 2 helper T-cell pathway seems to play a dominant role in the ocular immune response following airborne TiO 2 exposure.