Low mature TGF-beta 2 levels in aqueous humor during uveitis.

PURPOSE

To investigate whether transforming growth factor-beta 2 (TGF-beta 2), a strong immunosuppressive factor normally present in aqueous humor, is involved in the inflammatory process of clinical uveitis.

METHODS

Mature TGF-beta 2 levels were determined in aqueous humor samples of 9 patients with Fuchs' heterochromic cyclitis, aqueous humor samples of 21 patients with other uveitis entities, and vitreous fluid samples of 19 patients with uveitis by using a commercially available sandwich ELISA: Total TGF-beta 2 levels in ocular fluids were measured after heat activation. Aqueous humor samples from patients with cataract and glaucoma and vitreous fluid samples from eye bank eyes were tested as controls. Albumin levels, determined by radial immunodiffusion, were used as a measure of the disruption of the blood aqueous barrier.

RESULTS

Significantly lower mature TGF-beta 2 levels were detected in aqueous humor samples of patients with uveitis, compared to the two control groups without intraocular inflammation. Samples of patients with uveitis without detectable mature TGF-beta 2 did contain latent TGF-beta 2 levels (504 to 6024 pg/ml). In aqueous humor, there was a significant negative correlation between mature TGF-beta 2 and albumin levels. No mature TGF-beta could be detected in vitreous fluid. Total TGF-beta 2 levels in vitreous fluid were significantly lower in samples from patients with uveitis than in samples from eye bank eyes.

CONCLUSION

These results indicate that the mature TGF-beta 2 levels in aqueous humor and the total TGF-beta 2 levels in vitreous fluid are reduced during ocular inflammation. In aqueous humor, this might be caused by binding of mature TGF-beta to serum proteins, for instance, alpha 2-macroglobulin, or by a disturbance in the activation process of latent TGF-beta 2.