Isolation of human NK cells and generation of LAK activity.

This unit describes the preparation of natural killer (NK) cells from normal human peripheral blood and their incubation in vitro in the presence of interleukin 2 (IL-2) to yield lymphokine-activated killer (LAK) cells. A protocol is presented for isolating highly purified NK cell populations from PBMC, and another method presents steps for generating LAK cells from these purified NK cells via IL-2 stimulation. An alternate protocol describes the generation of LAK cells directly from whole, unseparated PBMC preparations instead of purified NK populations. The caveat with the alternate protocol is that LAK activity generated in this manner represents the total cytotoxic potential of all LAK precursor cells--i.e., all those PBMC that are capable of responding to IL-2 by up-regulation of cytotoxicity against NK-resistant targets. In PBMC, LAK precursor cells are found among subpopulations of both NK cells and T lymphocytes.