Please find the link for the following protocol:
ASSAY FOR NATURAL KILLER CELL ACTIVITY
NK cell activity is quantitated by determining the ability of peripheral blood mononuclear cells (PBMC) to lyse an NK sensitive target cell line (K-562). Target cells are labeled by incubation with radioactive chromium, washed, then added to a dilution series of PBMCs and incubated for 4 hours. Supernatants are harvested and the amount of intracellular chromium-51 released into the supernatant is measured with
a gamma counter. The amount of chromium-51 released is proportional to the lytic activity of the NK cells.