Immune deviation in relation to ocular immune privilege.

Immune privilege in the eye is a dynamic state in which the immune response to ocular Ags is molded and modified by the eye itself. Immune privilege correlates with systemic alterations in the immune response such that deviant forms of immunity emerge. The eye itself contributes to immune deviation, in part by displaying unique immunoregulatory factors in aqueous humor and expressed on ocular cells. When T cells encounter Ag in the eye, they can become anergic, undergo apoptosis, secrete TGF-beta, and/or release soluble regulatory factors containing the TCR alpha-chain. Ags taken up by indigenous APC escape the eye and reach the spleen where they activate a unique spectrum of Ag-specific T and B cells. The absence of systemic delayed hypersensitivity and complement-fixing Abs in this deviant response probably relates to the fact that inflammation is deleterious to vision and leads to blindness. Immune privilege is the eye's way of protecting its vital function from the ravages of immunopathogenic injury.