Natural killer cell biology and its effect on graft versus host disease

Natural killer (NK) cells were originally described in terms of their function. NK cells are of lymphoid origin and are found in the peripheral blood, spleen, and bone marrow, as well as other tissues. These cells are large, radio-resistant and granular lymphocytes that represent an important arm of innate immunity and are thought to play a critical role in the immune surveillance against tumors and virally infected cells. Allogeneic bone marrow transplantation (BMT) has proven to be an effective treatment for hematologic malignancies and some solid tumors. One of the major challenges of allo-stem cell transplantation (SCT) is to reduce the incidence and severity of GVHD while boosting the graft-versus-leukemia (GVL) effect. In the setting of allo-SCT, the reconstitution of NK cells is of notable interest due to their known capability to induce GVL without GVHD. Clinical applications of NK cells have been inspired by recognition of their potent anticancer activity. These studies discussed a solid basis for development of future NK cell trials for cancer therapy by minimizing risks and toxicities.