Natural killer cells in dengue hemorrhagic fever/dengue shock syndrome

Natural killer (NK) cell activity against K-562 target cells and HNK-1+ cell levels were serially determined in peripheral blood of 62 Thai children with dengue hemorrhagic fever/dengue shock syndrome aged 4-12 years and 59 age-matched normal controls. The studies were performed on febrile stage, 1st and 2nd day of subsidence of fever (shock stage), 3rd and 4th day of subsidence of fever (early convalescent stage) and once again on the late convalescent stage (approximately 14-18 days after subsidence of fever). The study revealed that during the course of disease the NK cell activity was not changed significantly from the normal controls. In contrast, the levels of HNK-1+ cells, which exhibited almost all NK and killer cell functional activities, were significantly decreased in the febrile and the shock stages and were normal in the early and late convalescent stages. The NK cell activity, on the per-cell basis, was significantly increased in the early disease stage when compared to that of the later period of the disease and of the normal controls. The study also revealed that patients with grade III of disease severity exhibited significantly more NK cell functional activities per cell than grade II on febrile stage and the first day of shock. These results suggest that natural killer cells were active in defense against dengue viral infection and might play some role in the pathogenesis of dengue hemorrhagic fever/dengue shock syndrome. Their functions might also determine the severity of the disease.