Immunomagnetic isolation of NK and LAK cells

The present study describes the immunomagnetic isolation of human natural killer (NK) and lymphokine activated killer (LAK) cells. Antibodies against CD56 and sheep anti-mouse IgG-coated magnetic monodisperse particles (Dynabeads M-450) were used for the positive isolation of CD56+ cells from unstimulated mononuclear cells (PBMC). A highly enriched population of CD56+ cells (less than or equal to 3% contaminating cells) was obtained with this method. The cellular yield of CD56+ cells was high (5.3% of the unseparated PBMC). The CD56+ cells remained unactivated after separation and preserved their functional characteristics, as measured by cytotoxic activity against the NK sensitive K562 cells. Incubating the CD56+ cells with IL-2 resulted in high LAK activity, as measured by cytotoxic activity against Daudi cells. Large numbers of functionally active CD56+ cells were obtained from IL-2 stimulated lymphocytes using anti-CD56 coated Dynabeads 450. A further enrichment of effector cells with LAK activity was accomplished by depleting the CD56+ cells for T-cells by anti-CD3 coated Dynabeads M450. The immunomagnetic isolation technique described was easy to perform, did not require expensive equipment and yielded NK and LAK cells of satisfactory purity.