Immune regulation and the eye.

The eye is an immune privileged site that is styled to maintain the visual pathway while at the same time provide defense against invading organisms. The eye does this by selecting immune responses that function in the absence of inflammation. Immune regulation by the eye takes the form of several active processes including a local immunosuppressive environment, the contribution of soluble factors, Fas-FasL-induced apoptosis and unique suppressive mechanisms used by pigment epithelial cells in the eye. These processes are so effective that antigens encountered in the eye result in specific systemic tolerization; a phenomenon akin to gut-induced oral tolerance. This review discusses the cellular and molecular basis of tolerance induction by the eye and notes the parallels to gut-induced peripheral tolerance.