Szemészet, 1975 (112. évfolyam, 1-3. szám)
1975 / 3. szám
Szemészet 112. 175—177. 1975. ,,Ophthalmiatrion” Eye Hosp. Athens, Greece Some Thoughts Concerning Prevention and Treatment of Graft Rejection in Keratoplasty* ,T. CHARAMIS and J. TSAMPARLAKIS The first successful full thickness corneal graft, which remained clear and transparent has been credited to Zirm (1905). Ever since, the progress in keratoplasty has been based mainly on the improvement of surgical techniques. It is interesting to notice that the increasing rate of success was connected from the very beginning, with a) the refinement of corneal surgery — in the sense of atraumatic surgery and b) the use of the best possible quality of donor material. This is not so with transplantation of other tissues and organs, where success was primarily related with a better understanding of immunology and transplantation biology. Why the cornea is an immunologically privilaged organ is now rather well understood: the privilage results largely from the “functional” — and of course the anatomical —• integrity and width of the barrier composed by the avascular host cornea around the graft. Normal or newly formed vessels and lymphatics must be as far away as possible from the graft margin. Hence the need for a) a graft centrally placed and of the smallest possible diameter — anyway less than 8 mm and b) for a meticulous pre-operative treatment of vascularization of the cornea and of any inflammatory reaction in the anterior segment of the eye. In fact, from a pure theoretical point of view, the allograft immune response, must be present in all cases of keratoplasty, without exception. And all we have to do is to create the appropriate conditions in oder to a) minimize the reaction to subclinical levels, or b) if it becomes strong enough to be clinically evident, to suppress it. We are familiar with the difficulties concerning diagnosis of allograft reaction; a real progress has been made by Khodadoust and co-workers who studied the clinical manifestations of this reaction in rabbit and human corneal transplantation; to-day we recognize in clinical practice its typical manifestation (rejection line); this is mediated usually by transcorneal efferent routes of the immunological reflex arcs. On the other hand, diffuse reaction — without the typical line — is not easy to be labelled as allograft response; this may probably mediated by transcameral roots (anterior uveal dilated vessels or diseased iris). Factors affecting the likelihood of a corneal allograft reaction, fall into three groups (BarrieR. Jones): those concerning the effective antigenic mass of the transplant, those concerned with the integrity of the barriers conferring privilage and those concerned with the immunological reactivity of the host. Research concerning problems of histocompatibility in keratoplasty, have shown that a) blood group incompatibility seems not to be important b) freezing of the donor material does not affect the antigenicity of surviving cells in a transplant and c) the HL—A system plays a role, not well determined for the time beeing. On the influence of the tissue-type compatibility on the fate of full thickness grafts, Gibbs et al. conclude that: a) The cornea with varying degrees of immunological privilage may be rather a delicate indicator of HL—A antigen/antibody reaction. * Dedicated to Professor M. Radnót on the 25th anniversary of her Professorship.] 175
