Immune privilege of the eye and fetus: parallel universes?

The eye is an extension of the brain and thus many of its tissues are incapable of regeneration. Ocular inflammation can produce extensive damage to innocent bystander cells leading to blindness. However, the eye possesses multiple strategies to control immune-mediated inflammation-a phenomenon known as immune privilege. The fetus of outbred mammals expresses paternal histocompatibility antigens and represents an allograft. However, the success of placental animals is a testament to the immune privilege of the allogeneic fetus. Extensive evidence suggests that the eye and the fetus employ similar strategies for establishing immune privilege for preserving vision and the unborn respectively.