[Cytolytic activity by lymphokines (LAK activity) in chronic myeloid leukemia]

Recent studies indicate that patients with chronic myeloid leukemia (CML) have a population of benign cytolytic cells (natural killer or NK) in their peripheral blood which may expand and activate in vitro in the presence of interleukin-2 (IL-2) leading to cytolytic cells activated by lymphokine or LAK cells (lymphokine-activated killer).

Thirteen patients with CML in the chronic phase of a median of 8 months (range: 1-43) in length and 13 healthy individuals were studied. The NK cells were separated from the peripheral blood by centrifugation by density gradient, elutriation and depletion in flasks with the CD5 and CD8 monoclonal antibodies. The resulting cell solution was cultivated in medium with IL-2 (1,000 U/ml) for 16 days with the count, phenotypic study and cytotoxicity tests of non adherent cells (LAK) being thereafter performed.

Following the separation, the CD56+/CD3- cells constituted 6.9 +/- 2.4% of the total of the patients with CML. At day 16 of the culture, the non adherent cells of the CD56+/CD3- phenotype (LAK cells) were found to be 57.9 +/- 4.4% of the total (expansion = 31 +/- 10.4 fold with respect to the initial number of NK cells). The LAK cells showed intense cytotoxic activity versus the killer-sensitive K562 cell lines (76.2 +/- 4.2% of lysis to the effector/target cell proportion 20:1 and 5.6 +/- 1.3% to the proportion 0.08:1) and Raji killer-resistant (65.7 +/- 4.3% and 3.8 +/- 1.6%, respectively). Thus, the grade of LAK cell expansion and their cytotoxicity in patients with CML were significantly lower than in healthy individuals.

Chronic phase patients with chronic myeloid leukemia may generate, in vitro, a population of LAK cells with intense cytotoxic activity in the peripheral blood.