ENHANCED HUMAN LYMPHOKINE-ACTIVATED KILLER-CELL FUNCTION AFTER BRIEF EXPOSURE TO GRANULOCYTE-MACROPHAGE COLONY-STIMULATING FACTOR

Background. Lymphokine-activated killer (LAK) cell function can be gen erated in peripheral blood mononuclear cells (PBMC) after brief exposu re of high dose interleukin-2 (IL-2) over the course of 1 or 2 days' c ulture in plain culture medium (IL-2-pulsed PBMC). The aim of the pres ent study was to investigate the ability of granulocyte-macrophage-col ony stimulating factor (GM-CSF) to augment LAK induction in low dose I L-2-pulsed PBMC derived from patients with cancer undergoing immuno-th erapy with IL-2. Methods. Peripheral blood mononuclear cells were coll ected from patients with cancer receiving a 5-day cycle of local (intr aperitoneal or intrapleural) infusions with IL-2. The cells were incub ated with IL-2 in the presence or absence of GM-CSF for 1 hour and the n tested as effecters against allogeneic tumor cells and LAK-sensitive cell lines. Results. Granulocyte-macrophage-colony stimulating factor at doses between 10 and 100 ng/ml was synergized with low dose IL-2 ( 100 IU/ml) in the generation of LAK activity in PBMC. Lymphokine-activ ate killer cell-mediated cytotoxicity derived from PBMC cultures incub ated with IL-2 and GM-CSF was significantly higher (up to three-fold) compared with that generated with IL-2 alone. The GM-CSF-induced enhan ced LAK activity was maintained when tested at day 5. GM-CSF increased the percentages of IL-2 receptor (R) positive ((+)) and CD8(+) cells in the IL-2-pulsed PBMC. In contrast to CD56+ cells, highly purified C D8+ cells isolated from PBMC pulsed with IL-2 and GM-CSF responded wit h increased LAK activity, thus representing the cell-type that mediate s the augmenting effect of GM-CSF. Major histocompatibility complex (M HC) molecules or the CD3 surface antigens were not involved in the GM- CSF-mediated enhancement of LAK induction because anti-MHC class I and class II monoclonal antibodies (MoAb) or MoAb against the CD3 molecul es remained without any effect in this system. The GM-CSF-mediated LAK -enhancement was IL-2-dependent because MoAb against IL-2 receptor com pletely inhibited the generation of LAK activity. Conclusions. The use of GM-CSF for the enhancement of IL-2-induced LAK activity in 1 hour cultures may improve clinical results in cancer immunotherapy. In addi tion, implementation of this procedure could eliminate the high cost o f cell culture which usually accompanies IL-2/LAK cell therapy as well as eliminate the known toxic side effects associated with this kind o f therapy.