Effect of human interleukin 3 on the susceptibility of fresh leukemia cells to interleukin-2-induced lymphokine activated killing activity.

Pretreatment of acute myeloblastic leukemia cells with the hemopoietic growth factor interleukin 3 (IL3) increased their susceptibility to lymphokine activated killing (LAK) but did not affect their constitutive resistance to native natural killer activity. In addition, IL3 treatment did not alter the LAK cell-mediated killing of CD34+ hemopoietic progenitors present in normal bone marrow. Increased 3H-thymidine uptake was generally observed after IL3 treatment. However, failure to proliferate in response to IL3, observed in some cases, did not prevent changes in LAK susceptibility. Enhanced lysis of IL3-treated leukemic cells was accompanied by a moderate increase of the effector-target binding. Increased LAK susceptibility was already observed at 18 h, while optimal cytolysis and expression of the cell adhesion molecule (CAM) LFA-3 (CD58) by IL3-treated AML cells were concomitantly observed at later culture times. In contrast, the CAM ICAM-1 (CD54) was not modulated by IL3, nor were significant changes in the expression of either CAMs observed in normal hemopoietic cells. Blocking experiments with the anti-CD58 monoclonal antibody demonstrated a variable neutralizing effect on the IL3-induced increase of LAK activity, depending on the leukemia cell studied. The effect described here, together with the known role of IL3 in normal hemopoiesis makes it a factor of potential therapeutic value for the treatment of leukemic patients.