Immunity in the eye: lessons in organ-specific responses.

Fifty-five years have past since Sir Peter Medawar first demonstrated that the fate of allografts differs in the skin, brain, subcutaneous tissue, and anterior chamber of the eye. Indeed, these and other experiments performed at the University of Birmingham and University College London not only helped define key paradigms in transplantation biology but introduced the concept of immune privilege in the eye and in other tissues. In the ensuing years, the work from dozens of laboratories has confirmed that immune responses in eye, although sharing many features with immunity in other tissues, are atypical in many respects. This has been hypothesized to stem from the requirement in the eye to hold inflammation in check to preserve visual function. Indeed, inflammatory reactions in different regions of the eye can result in visual impairment and blindness, manifesting in diseases such as vernal keratoconjunctivitis, uveitis, corneal endotheliitis, Mooren's ulcer, and pemphigoid. The investigation of the cell and molecular basis of the unique nature of immunity in the eye has revealed a remarkably complex network of interactions that controls inflammation while affording immunity. The most recent data generated in this field and the concepts arising from their interpretation were discussed at a symposium held at the University College London in late 2002. Here, we highlight some of the findings discussed at the meeting and introduce in-depth reviews published in this issue of the journal.