Roles and mechanism of natural killer cells in clinical and experimental transplantation.

Natural killer (NK) cells are an important component of the innate immune response against intracellular pathogens and also play a role in the tissue inflammation associated with autoimmune diseases. Being a potent effector response, it must be well regulated in order to avoid unwanted destruction of normal tissues. Indeed, NK cells are unique in bearing both stimulatory and inhibitory receptor tolerance. The fine balance between activation and inhibition that decides their final action provides an opportunity for their possible modulation in specific therapeutic settings. The recent evidence implicating NK cells in promoting tolerance during allotransplantation is one such setting that has important implications for a successful transplant. This review provides an insight into NK cell biology and their involvement in allotransplant tolerance.