Natural killer cells in connective tissue disorders.

NK cells may be important in the elimination of cells infected by virus, in the regulation of antibody production, and in tissue destruction. The significance of NK cells in rheumatic disorders is unknown, but NK cells and NK-like cells have been found in the peripheral blood and synovial tissues of patients with autoimmune disease. In particular, defects in NK cell activity have been reported in SLE, RA, PSS and SS. Of these diseases, SLE appears to be the best characterized with obvious abnormalities in NK cell numbers, impaired cytotoxicity of individual NK cells, decreased release of cytotoxic factors, deranged IFN modulation of the NK cell, and associated abnormalities in the IL-2 system. The association of these abnormalities with the underlying disease process is currently under investigation.