Background: Recent reports have revealed the importance of several cytokines in chronic conjunctival allergic diseases (ACD) such as vernal keratoconjunctivitis (VKC) and atopic keratoconjunctivitis (AKC). Osteopontin (OPN) is a noncollagenous adhesive matrix protein that is expressed by activated macrophages. There has been considerable interest in the potential role of OPN in monocyte infiltration at sites of inflammation. We measured OPN level in tears using ELISA, to determine whether the level of this cytokine is elevated in ACD.
Methods: The level of OPN in tears was measured by ELISA using samples from patients with VKC, AKC or allergic conjunctivitis (AC) and from normal subjects. The level of OPN in tears was compared with the clinical severity of ACD and serum level of total IgE.
Results: The level of OPN in tears in AKC patients was significantly higher than that in AC and normal controls. Tear level of OPN in patients with VKC was also significantly elevated compared to those with AC and to normal controls. The clinical severity of ACD correlated significantly with the level of OPN. However, no correlation was observed between tear OPN level and serum level of total IgE.
Conclusions: These results indicate that OPN plays an important pathophysiological role in severe ocular allergic conditions and that an elevated level of OPN in tear fluid reflects the local clinical status of ocular allergy, which may be an example of tissue remodeling.