Host response to allogeneic implants in the anterior chamber of the rat eye.

The anterior chamber of the eye has long been considered an immunologically privileged site, but the nature of this privilege has been re-examined recently. In our study, we used rats with defined genetic differences as the donors and the recipients. Implants were from split-ear sections, and the host response was measured both in vivo, by implant survival time, and in vitro, by the mixed-leukocyte reaction and the 51Cr-release cytotoxicity assay. Controls consisted of syngeneic implants and allogeneic orthotopic skin grafts. This study has shown that (1) host sensitization occurs approximately 7 days after implantation, (2) cytotoxic effector cells are produced by day 14, with a peak on day 21, (3) implant survival time is long in spite of the presence of competent effector cells, and (4) the survival time of implants is directly related to the degree of genetic histoincompatibility. The reasons for the long implant survival in hosts with a demonstrable immune reactivity has not been established, but the survival time appears to be related to the route of sensitization (vascular rather than lymphatic), which lends itself to the production of serum blocking factors and the procurement of supressor T cells.