As introduction to a light-and electron-microscopial examination of rejected human corneal grafts a summary is given of the clinical signs of rejection. It is extremely important to recognize these signs in time and to initiate the correct therapy. Most failures in corneal transplantation are due to rejection. Rejection reactions are often not recognized early enough. The differential diagnosis is difficult because so many factors can trigger off a rejection. As the diagnosis is so often missed it is a good thing to consider the clinical picture of graft rejection once more. Maumenee: 'most ophthalmologists do not recognize the signs of early graft failure and usually do not refer the patient back for therapy until considerable oedema has developed from endothelial destruction' (1962). In the cases with a good prognosis the rejection percentage is + 12%; in vascularized corneas and complicated corneal transplantations as high as 75% (Polack, 1977).
COURSE OF THE IMMUNOLOGICAL REACTION
Lymphocytes from the graft migrate like inquisitive scouts and come into contact with the recipient's lymphocytes. The 'enemy' is recognized by the recipient and 'troops' are mobilized to attack the graft. In the first months after the transplantation the wound in Descemet's membrane is not completely closed and the 'killer-cells' can reach the endothelium of the graft through this wound (Inomata, 1970;Polack, 1973). This is the quickest route and for this reason the first months are most critical. Rejection begins