An exploratory study of neopterin and kynurenine pathway in pterygium

Abstract Pterygium is an inflammatory, vascular and degenerative disorder with unknown aetiology. The aim of this study was to evaluate the changes in neopterin levels, reflecting T-cell immunity, and the kynurenine pathway, the main degradation process of tryptophan, in pterygium. For this purpose, neopterin concentrations were measured in serum and tear samples by enzyme-linked immunosorbent assay (ELISA) in pterygium patients (n=31) and control group (n=32). Kynurenine (KYN) and tryptophan (TRP) serum levels were simultaneously determined by high-performance liquid chromatography (HPLC) for evaluation of the kynurenine pathway. Serum neopterin concentrations and kynurenine to tryptophan ratio (KYN/TRP) as an index of tryptophan breakdown were found increased in pterygium compared to controls (p<0.05). Although there was a 3-fold difference observed between serum and tear neopterin levels, no significant relationship was found. It can be concluded that neopterin may be used as a nonspecific biomarker that reflects immunological activity in pterygium and has clinical potential for evaluation of pterygium pathogenesis. These immune- or inflammatory-mediated changes were also supported by an increased KYN/TRP ratio in pterygium patients.