Kinetics of corneal transplant rejection in the rat penetrating keratoplasty model

Kinetic changes of inflammatory cells and major histocompatibility (MHC) antigenic markers in syngeneic and allogeneic corneal grafts in rats were studied. Syngeneic grafts demonstrated mild inflammation in the first week with macrophages and T-helper/inducer cells found in a 2:1 ratio. By week 2 fewer macrophages were seen, and by week 4 no inflammatory cells were seen in the central graft. Central keratocytes and endothelium were negative for class II MHC expression. Significant inflammation persisted adjacent to the wound with macrophages and T-helper/inducer cells seen surrounding the sutures. Allogeneic grafts in the first week demonstrated mild inflammation with macrophages and T-helper/inducer cells in a 2:1 ratio. The central graft in week 2 had increased numbers of T-helper/inducer cells and T- suppressor/cytotoxic cells. By the third and fourth week, the T- suppressor/cytotoxic cells had become the major infiltrating cell. MHC class II antigens were seen on inflammatory cells, keratocytes, donor, and recipient endothelium.