The functional role of natural killer cells early in clinical sepsis

Although much information is available for the function of circulating monocytes when signs of sepsis are apparent, little is known for natural killer (NK) cells. NK cells were isolated from 10 healthy controls and from 103 patients with sepsis within the first 24 h from diagnosis. NK cells were stimulated with lipopolysaccharide for cytokine production. Release of tumor necrosis factor-alpha and of interleukin (IL)-6 was below the limit of detection. Release of IL-23 and of interferon-gamma (IFNγ) was significantly greater among patients than among healthy volunteers. Release of IFNγ was pronounced in septic shock. Patients were divided into two subgroups based on the ratio of IFNγ to IL-23 released by the NK cells after stimulation: those with ratio ≤5 and 28-day survival 13.5%, and those with ratio >5 and 28-day survival 29.4% (p: 0.048). It is concluded that early after clinical development of sepsis, NK cells remain active for the production of IFNγ. Their activity is associated with the final outcome.