In vitro demonstration of human natural killing of keratocytes and corneal epithelium

Cultured human corneal keratocytes or fresh human lamellar corneal epithelial sections were used as target cells in a monolayer cytotoxicity assay. Fresh allogeneic nonadherent peripheral blood mononuclear cells were incubated with the corneal-cell populations and assayed for lymphocyte binding and target-cell cytotoxicity by acid-violet-49 vital staining. Primary keratocyte populations bound lymphocytes, and there was subsequent keratocyte dye uptake. Corneal epithelium did not show either binding or lymphocyte-mediated cytolysis. These data suggest that nonspecific and spontaneous lymphocyte-mediated cytolysis of keratocytes occurs in vitro and that the responsible lymphocyte subpopulation has functional activities and cellular morphology characteristic of the natural-killer cell. This activity may play a role in initiating specific corneal-graft rejection.