Natural killer cell activity against a thymoma cell line Thy 121 in bone marrow transplant recipients.

Twenty-one patients with acute and chronic leukemia or severe aplastic anemia were studied for NK activity against a thymoma cell line (Thy 121) before and after allogeneic bone marrow transplantation. The means of the pretransplant and post-transplant levels did not differ from the mean of 134 NK determinations in 67 healthy donors. There was no correlation between pretransplant NK levels and the appearance of graft-versus-host disease. Three weeks following bone marrow transplantation, pretransplant NK levels were observed. The sensitivity of NK cells to interferon was the same as in normal donors both before and after bone marrow transplantation. In contrast to methotrexate, cyclosporin A inhibited NK activity in patients and controls in vitro. In vivo cyclosporin A treatment, however, did not decrease NK levels in bone marrow recipients.