Vitreous body affects activation and maturation of monocytes into macrophages.
BACKGROUND
Macrophages play an important role in several ocular diseases. Because macrophages localized in ocular tissues may be derived from blood monocytes, the effect of vitreous [containing transforming growth factor-beta 2 (TGF-beta 2) and hyaluronic acid] on blood monocytes, maturating in the tissue to macrophages, was determined.


METHODS
Human monocytes were cultured with and without vitreous in RPMI 1640 medium containing human AB serum. As a parameter of activation the release of interleukin-6 was measured by the B9 bioassay; as an indication of maturation, the content of acid phosphatase and the increase in cell 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, interleukin-6 than control monocytes. Vitreous at 20% significantly (P = 0.0075) reduced the amount of acid phosphatase by 80% over a 4-day culture period. This reduction was partially eliminated with neutralizing antibodies to TGF-beta (P = 0.0014). Furthermore, human recombinant TGF-beta 2 increased the activity of acid phosphatase in monocytes at 1.25 ng/ml and reduced it (P < 0.0001) at higher concentrations (5-10 ng/ml). Hyaluronic acid showed an effect additive to that of TGF-beta in further diminishing the amount of acid phosphatase (P = 0.026).


CONCLUSIONS
Vitreous exerts a regulatory effect on monocyte activation and maturation by its content of TGF-beta and possibly hyaluronic acid and may, thus, modify the inflammatory or immune response in the eye.
Department of Ophthalmology, School of Medicine, University of Southern California, Los Angeles, USA.
R
R
Osuský
S M
SM
Walker
S J
SJ
Ryan
D000135:Acid Phosphatase / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism; D008262:Macrophage Activation / Q000502:physiology*; D008264:Macrophages / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D009000:Monocytes / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D014822:Vitreous Body / Q000502:physiology*
D015850:Interleukin-6; D016212:Transforming Growth Factor beta; D000135:Acid Phosphatase