Aqueous Humor Induces Transforming Growth Factor-β (TGF-β)-Producing Regulatory T-Cells

Abstract

Purpose: The intraocular microenvironment is an immuneprivileged site where immunogenic inflammation is suppressed. Suppression of immunogenic inflammation has been associated with immunosuppressive factors found in aqueous humor produced by ocular tissues. To further understand the mechanisms suppressing immunogenic inflammation in the eye, we have examined the production of lymphokines by primed T-cells activated in the presence of aqueous humor. Methods: Enriched in vivo primed T-cells were T-cell receptor-stimulated in the presence of fresh aqueous humor. The culture supernatant was assayed for IFN-γ and IL-4 by sandwich ELISA. TGF-β production by T-cells stimulated in the presence of aqueous humor was assayed by a TGF-β bioassay of the culture supernatant and by quantitative RT-PCR for TGF-β1 mRNA expression. Aqueous humor-treated T-cells were assayed for their capacity to suppress IFN-γ production by stimulated, primed T-cells. Results: Aqueous humor-enhanced proliferation but irreversibly suppressed production of both IFN-γ and IL-4 by in vitro-activated, in vivo-primed T-cells. Aqueous humor induced in vivo primed T-cells to produce TGF-β in vitro, and these TGF-β-producing T-cells suppressed IFN-γ production by other T-cells activated in co-cultures. Conclusions: Aqueous humor alters the functional program of TCR-ligand-activated, primed T-cells, converting the cells to TGF-β-producing regulatory cells. Curr. Eye Res. 16: 900–908, 1997.

KEYWORDS:

• aqueous humor
• cytokines
• delayed type hypersensitivity
• immunomodulators
• T-lymphocytes
• tolerance