Anterior chamber-associated immune deviation: a review of the anatomical evidence for the afferent arm of this unusual experimental model of ocular immune responses

Anterior chamber-associated immune deviation (ACAID) is an animal model of tolerance induced experimentally by the injection of antigen into the anterior chamber of the eye. The unusual deviant immune response has both afferent and efferent arms and it is the former that is the focus of this review. The paradigm states that antigen injected into the anterior chamber of the eye is internalized by intraocular antigen presenting cells (APCs) which then migrate largely to the spleen to induce the differentiation of regulatory T cell populations which in turn form the basis of the modified efferent arm to the deviant immune response. However, the migration routes of ocular APCs or free antigen to the secondary lymphoid organs remain unclear. In this review we will discuss the evidence for different possible afferent routes by which antigen (either free or cell-associated) leaves the eye and the pattern of distribution to secondary lymphoid organs.