Decreased natural cell-mediated cytotoxicity per effector cell in acquired immunodeficiency syndrome.

Natural cell-mediated cytotoxicity (CYT) was determined using whole blood samples from 32 patients with the acquired immunodeficiency syndrome (AIDS) and 12 with AIDS-related complexes (ARC) and correlated with the number of putative natural killer cells (NK) bearing surface marker Leu 11a. Mean percent cytotoxicity (%CYT) was significantly lower in AIDS and ARC patients compared to that of normal controls. Mean %NK cells in AIDS patients was significantly higher than in normals, while %NK cells in ARC patients did not differ significantly from that of normals. In contrast, the absolute number of NK (NNK) cells in AIDS patients did not differ significantly from that of normals, while the NNK cells in ARC patients was significantly lower than those in normals. When the data were expressed in kinetic lytic units per NK cell (KLU/NK = maximum number of K562 cells killed per NK cell in 4 hours), significantly lower KLU/NK were observed in both AIDS and ARC patients compared to that in normals. Our data show that NK cells in AIDS and ARC patients are in a less active state compared to those in normals.