[Why HLA-typing in keratoplasty? A review]

Due to the absence of vessels and lymph drainage, human cornea is the tissue grafted with the greatest success. From an immunological point of view, this advantage is lost when the recipient cornea has pronounced vascularization and is sensitized. In such cases, which have a poor prognosis, the postoperative success rate drops to below 50% due to graft rejection. The origin and point of attack of the immune reaction to the graft are the MHC antigens of the donor cornea, which occur on almost all nucleated cells. Since they are capable of triggering a T cell activation in the recipient they set immunological effector mechanisms in motion which lead to elimination of the cells carrying the alloantigen. Corresponding to the MHC antigen expression (both Class I as well as Class II) on all cells in all layers of the cornea, rejection reactions of all the various cell types (epithelial, stromal, endothelial) are also seen. By using histocompatible donor corneas it is possible to influence the afferent arm of the immune response preoperatively and thus to diminish its effect on the postoperative course.