In vitro susceptibility of acute leukemia cells to the cytotoxic activity of allogeneic and autologous lymphokine activated killer (LAK) effectors: correlation with the rate and duration of complete remission and with survival.

Acute lymphoblastic leukemia (ALL) and acute myeloblastic leukemia (AML) blasts were studied for their sensitivity to the lytic activity of normal allogeneic interleukin 2 (IL-2) activated killer (LAK) cells, and of autologous LAK effectors generated at the time of complete remission (CR). In 12 of 23 ALL cases (52%), the blasts were susceptible to normal LAK cells (> 15% lysis) and ten of them achieved a CR. Of the remaining 11 LAK-resistant cases, seven obtained a CR. No correlation was found between susceptibility to LAK activity, cytomorphology, immunophenotype, CR duration and survival. Eighteen of the 26 AMLs tested (70%) were susceptible to normal LAK cells, and nine of the 13 cases studied (70%) were also lysed by autologous LAK effectors generated at CR. No clearcut correlation was observed between blast sensitivity to normal LAK cells and morphologic cytotype, though a higher incidence of resistant cases was observed in the M4 subgroup. All AMLs susceptible to normal LAK cells but one achieved a CR, while this occurred only in three of the eight resistant cases (p = 0.004). The median survival and event-free survival duration in the resistant patients were significantly shorter (p = 0.03 and p = 0.02, respectively) compared to those of the susceptible patients. In ten ALL and in six AML, which at presentation displayed less than 10% circulating blasts, the susceptibility of the leukemic population to normal and autologous LAK effectors could be tested, both at diagnosis and at remission. All cases but one were resistant to autologous LAK cells generated at diagnosis, while at CR, seven cases (four ALL and three AML) became susceptible to autologous LAK cells (p = 0.01). The remaining nine were resistant to both allogeneic and autologous LAK effectors. Taken together, these findings suggest that in AML, but not in ALL, the LAK cell compartment may play a role in the clinical course and overall outcome of the disease.