Histopathological and histochemical alterations in the early stages of corneal graft rejection.

Rejection of corneal grafts was produced in rabbits after skin from the corneal donor was grafted subcutaneously. Clinical observations showed that the graft sickness started at the periphery of the graft after blood vessels from the host cornea reached the scar. Histologic studies demonstrated that the scar tissue was first invaded by vessels and infiltrated by lymphocytes, monocytes, and plasma cells. This infiltrate reached the endothelium through the gap in Descemet's membrane. The early histological picture of the graft sickness was characterized by endothelial destruction and infiltration at its junction with the scar. Keratocytes changed in shape and apparently became active fibroblasts. Decreased amounts of ground substance in the early stages of rejection, as indicated by appearance of haziness in the graft, were indicated in sections by a decrease in metachromatic staining. Diminished uptake of radioactive sulfate also occurred in the early stages of the graft sickness; which was followed by an elevated uptake of sulfate as the graft became opaque and filled with active fibroblasts.