Large-scale ex vivo expansion and characterization of natural killer cells for clinical applications.

Background Aims: Interest in natural killer (NK) cell-based immunotherapy has resurged since new protocols for the purification and expansion of large numbers of clinical-grade cells have become available.

Methods: We have successfully adapted a previously described NK expansion method that uses K562 cells expressing interleukin (IL)-15 and 4-1 BB Ligand (BBL) (K562-mb15-41BBL) to grow NK cells in novel gas-permeable static cell culture flasks (G-Rex).

Results: Using this system we produced up to 19 × 10(9) functional NK cells from unseparated apheresis products, starting with 15 × 10(7) CD3(-) CD56 (+) NK cells, within 8-10 days of culture.