GENERATION OF CYTOTOXIC T-LYMPHOCYTES FROM PERIPHERAL-BLOOD OF LEUKEMIC PATIENTS

Peripheral blood mononuclear cells from 13 patients with acute leukaem ia were used to establish long-term interleukin-2-dependent cytotoxic T lymphocytes. Cells were grown in RPMI medium containing interleukin- 2 (IL-2, 100 U/ml) and 2.5% conditioned medium prepared by activating normal lymphocytes with phytohaemagglutinin. Proliferation of IL-2-dep endent CD3-positive lymphocytes was seen in 1 of 2 acute lymphocytic l eukaemia cases (ALL), 1 of 4 acute myelogeneous leukaemia cases (AML) (M1) and 8 of 8 more differentiated AML. In 2 cases with detectable le ukaemic cell markers (1 ALL and 1 AML) passageable cells were develope d, that expressed normal T cell phenotypes (namely CD3, CD4 and CD8) a t the expense of leukaemic cells. In 1 of 2 cases, long-term IL-2-cult ured cells showed specific cytotoxic activity against autologous leuke mic cells. The percentage killing against autologous and two allogenei c target cell lines at a 50/1 effector/target (E/T) ratio was 42%, 9% and 19% respectively. Similarly the cytotoxic activity of IL-2 activat ed from 4 different individuals against conventional tumour targets K5 62 and Daudi at a ratio of 50/1 was 29%-68% (median = 55%) and 34%-78% (median = 61%) respectively. It was also found that this killing pote ntial of the activated cells was maintained for as long as culture was continued (median 23 days, range 17-75 days). The mechanism(s) of T c ell proliferation at the expense of leukaemic blast cells in the case of a minority of leukaemic patients and the possible clinical therapeu tic potential of these cells following in vitro IL-2 activation deserv e further investigation.