CYTOTOXICITY AGAINST HUMAN LEUKAEMIC CELLS.

Antibodies which are to induce the killing of allogeneic myeloblasts by normal lymphoid cells have been found in a high proportion of patients with acute myeloid leukaemia. The cytotoxic mechanism induced by this antibody activity is shown to be highly effective in terms of the number of myeloblasts which can be killed by a given number of lymphoid cells and the antibody concentration needed to induce killing. Reasons for the in vivo failure of this cytotoxic mechanism, assuming that antibodies occur against autologous myeloblasts, are suggested by studies in which the cytotoxic lymphoid population has been monitored serially. Some patients are shown to have almost undetectable levels of cytotoxic effector cell activity. A further reason for the failure of this mechanism related to 'blocking activity' in the serum is being investigated. Preliminary results suggest that assay of this antibody activity against myeloblasts may also be of value in following the response to immunotherapy and in providing early warning of relapse. It is suggested that the demonstration of antibody-dependent lymphocyte activity against acute myeloid leukaemic cells provides an additional insight into this disease which may have important implications in management and therapy of acute myeloid leukaemia. [ABSTRACT FROM AUTHOR]