Positive effect of direct current on cytotoxicity of human lymphocytes.

Normal or leukemic human lymphocytes treated with direct current (DC) showed enhanced antileukemic cytotoxicity. The enhancing effect of DC-treated lymphocytes was dependent on current density and time exposure. A desirable effect was achieved with current densities ranging from 5 to 10 mA/cm2 at a short exposition time (5--10s). Enhanced lymphocyte cytotoxicity occurred after a 48 h cultivation at 37 degrees C in a humidified atmosphere containing 5% CO2 and was proved by the increased number of trypan blue stained target cells, tumor-binding cells, and lymphocytes with activated nucleoli. Lymphocyte cytotoxicity measured immediately after DC-treatment was not enhanced. Furthermore, the cytotoxic effect was potentiated using media conditioned with interleukin-2 (IL-2) or cytosol fraction (F3) isolated from human leukemic cells. Such in vitro stimulated cytotoxic cells displayed reactivity against K 562 cells as well as fresh leukemic cells of allogeneic origin. Of considerable clinical interest is the observation that lymphocytes treated with DC in IL-2 or F3 conditioned media may enhance antileukemic cytotoxicity in peripheral lymphocytes of patients with hematological malignancies.