Abstract
When natural killer (NK) cells work as effectors for cytolysis, they first recognize and bind to a target cell, and then lyse the bound target by releasing lytic materials such as NK soluble cyto-toxic factors (NKCF). After killing the target, NK cells detach from the dead target and repeat this lytic sequence by the recycling capacity. Thus, the impairment of NK cell activity results from (1) a decreased number of NK cells, (2) defective binding, (3) defective lysis, or (4) impaired recycling. Ac-tually, in the case of (1), numbers of total NK cells or active NK cells are decreased or absent in new-borns, Chediak-Higashi syndrome, severe combined immunodeficiency, and hemophagocytic lymphohistiocytosis ; in (2), NK cells have defective target binding capacity in newborns and LFA-1 (lymphocyte function-associated antigen-1) /Mac-1 /p 150, 95 deficiency; in (3), there is defective NK cell cytolysis in newborns, leukemia, myelodysplastic syndrome (MDS), erythematosus, Chediak-Higashi syndrome, and a familial NK cell deficiency with defective NKCF production; and in (4), NK cells are impaired in the recycling in newborns, leukemia, Chediak-Higashi syndrome, and congenital neutropenia. Some clinical and laboratory data of our representative cases are presented for better understanding of NK cell dysfunctions.
