VITREOUS BODY AFFECTS ACTIVATION AND MATURATION OF MONOCYTES INTO MACROPHAGES

Background: Macrophages play an important role in several ocular disea ses. Because macrophages localized in ocular tissues may be derived fr om blood monocytes, the effect of vitreous [containing transforming gr owth factor-beta 2 (TGF-beta 2) and hyaluronic acid] on blood monocyte s, maturating in the tissue to macrophages, was determined. Methods: H uman monocytes were cultured with and without vitreous in RPMI 1640 me dium containing human AB serum. As a parameter of activation the relea se of interleukin-6 was measured by the B9 bioassay; as an indication of maturation, the content of acid phosphatase and the increase in cel l size were assessed. Results: Monocytes in vitreous-containing medium grew more slowly than did control monocytes. Monocytes cultured in 10 % vitreous released 51% less, and in 20% vitreous 73% less, interleuki n-6 than control monocytes. Vitreous at 20% significantly (P=0.0075) r educed the amount of acid phosphatase by 80% over a 4-day culture peri od. This reduction was partially eliminated with neutralizing antibodi es to TGF-beta (P=0.0014). Furthermore, human recombinant TGF-beta 2 i ncreased the activity of acid phosphatase in monocytes at 1.25 ng/ml a nd reduced it (P<0.0001) at higher concentrations (5-10 ng/ml). Hyalur onic acid showed an effect additive to that of TGF-beta in further dim inishing the amount of acid phosphatase (P=0.026). Conclusion: Vitreou s exerts a regulatory effect on monocyte activation and maturation by its content of TGF-beta and possibly hyaluronic acid and may, thus, mo dify the inflammatory or immune response in the eye.