The good, the bad and the ugly--APCs of the eye.

Dendritic-cell (DC) populations throughout the body have a wide range of features in common, which are associated with their primary function in antigen presentation. The unique immune milieu of the anterior segment of the eye is characterized by a selective DC-dependent inability to develop delayed hypersensitivity responses following antigen invasion into the eye. Recent research papers provide evidence that different maturation stages of DC subsets are detectable at different corneal sites. Thus, the corneal DC, as well as the DC and the macrophages in the iris and ciliary body, have the potential of determining the outcome of immunity or tolerance within this organ.