Human natural lymphocyte effector cells: definition, analysis of activity, and clinical effectiveness.

Lymphokine-activated killing has enormous potential in the treatment of cancer. Lymphoid effectors have the potential to recognize and lyse a wide array of tumor cells, a phenomenon which has been seen in vitro and to some extent in vivo. However, studies have indicated that complexity exists not only in the nature of the lymphocyte that can be activated ex vivo for therapeutic use, but also in the delivery of such therapy in a clinical setting. This review attempts to deal with both issues. The nature of the cells mediating lymphokine-activated killer activity, their heterogeneous phenotype, their activation requirements, and a hypothetical mechanism of action are discussed. In addition, previous clinical studies are reviewed and key issues are raised that need to be addressed in upcoming clinical trials.