Diminished reactivity to alloantigen following transplantation of cultured thymic fragments.

Transplantation of allogeneic thymus into thymic deficient individuals will restore T-cell function including ability to demonstrate alloreactivity. In allogeneically reconstituted athymic (nude) mice, alloreactivity as manifested by positive mixed leukocyte reactivity, cell mediated lympholysis and skin graft rejection is present for all alloantigens, save those of the thymus donor. Such reconstituted animals possess double tolerance, for self and for donor. Cultured thymic fragments have been used to correct the immunodeficiency of thymic deficient humans. In a patient with severe combined immunodeficiency who acquired T-killer activity after allogeneic cultured thymic fragment transplant, mixed leukocyte response to the thymus donor was nearly absent. Patients with cancer of the lung, although not profoundly T deficient, received cultured thymic fragments in a project designed to enhance their immunity. Diminished alloreactivity for donor cells was seen in 2 of 3 such patients.