Purification of human natural killer cells using a clinical-scale immunomagnetic method

Infection, graft failure, disease relapse, and GvHD are significant adverse events associated with allogeneic BMT. Although donor leukocyte infusion has been used to prevent or to treat infection, graft failure, and relapse, the potential clinical benefits are often outweighed by the risk of T cell-mediated GvHD. Results from animal studies suggest that donor natural killer (NK) cells may be an ideal cell type for prevention or treatment of these adverse events. We have therefore sought to develop an automated, efficient, and clinical-scale human NK cell-purification method. Twelve leukopheresis products were purified for NK cells using a twostep immunomagnetic method. CD3+ cells were first depleted from the apheresis products. CD56+ cells were then enriched from the CD3+ cell-depleted products. The median percentage of CD3–CD56+ NK cells in the final products was 91.0%, and the median recovery was 48.7%. The median depletion for CD3+CD56– T cells was 5.3 log. Natural cytotoxicity of the purified cells was approximately five-fold higher than that of unpurified mononuclear cells, and it could be further increased by stimulation of the purified cell with IL2. We described a large-scale purification method for automated, efficient, and rapid isolation of human NK cells that yielded minimal contamination with T cells or B cells. These purified NK cells may be expedient for preclinical and clinical uses.