Phenotypic and functional analysis of synovial natural killer cells.

Natural Killer (NK) cells are cells of the innate immune system with characteristic effector functions, including recognition and lysis of virus-infected or tumor cells and production of immunoregulatory cytokines, particularly interferon-gamma (IFN-gamma). NK cells account for between 10 and 15% of peripheral blood lymphocytes and are also present in synovial fluid and tissue where they might potentially contribute to amplification of the inflammatory process through interactions with macrophages and dendritic cells. This chapter outlines methods of assessing the phenotype of NK cells through analysis of NK-cell markers and the function of NK cells through cytotoxicity assays and measurement of cytokine production.