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Cytotoxic effector cells mediating natural killing (NK), antibody-dependent cellular cytotoxicity (ADCC), and lectin-dependent cellular cytotoxicity (LDCC) were studied in patients with leukemia or aplastic anemia before and/or after marrow transplantation. Before transplantation, about one-third to one-half of the patients were deficient in cytotoxic activity. In patients with leukemia, this was most likely due to large numbers of circulating blast cells diluting or replacing the effector cells. In patients with aplastic anemia there was an apparent absence of the effector cells in a proportion of the patients. After marrow transplantation, cytotoxic activity in all three systems returned to normal rapidly, by 30 days, and remained so through 100 days. However, about 20% of patients studied beyond 1 year were deficient in these functions. There were no significant associations between cytotoxic activity and important clinical parameters including infections, graft-vs-host disease, and recurrence of leukemia. Our findings do not support an immunosurveillance role for NK against leukemia after marrow transplantation. Furthermore, they point out the need for new in vitro approaches for meaningful monitoring of marrow transplant patients. Finally, our results showed a significant discordance between NK, ADCC, and LDCC activities in these immunologically perturbed individuals, indicating that either different cell populations or different cellular mechanisms are involved in these cytotoxic functions.
Livnat et al. (Tue,) studied this question.