Functional abnormalities of natural killer cells in childhood hemophagocytic syndrome

To analyze the abnormality of natural killer (NK) cells in childhood hemophagocytic syndrome (HPS), we investigated the numbers, cytolytic functions of circulating NK cells, and responsiveness to cytokines by flow cytometry, ⁵¹Cr-releasing and single-cell assay in 13 patients. In the active phase, the relative number of CD 16⁺ cells was decreased in 3 patients. NK activity was depressed in 6 patients but normal in the remaining 7 in the active phase. Lymphokine-activated killer (LAK) activity showed the similar tendency. The responsiveness of NK cells to IFN-γ was absent, but that to IL-2 was normal in the active phase. Single-cell assay showed depressed maximal recycling capacity (MRC) and killing capacity values in the active phase and in remission phase, respectively. From these results, NK cells have such functional abnormalities as the absence of responsiveness to IFN-γ and depressed recycling capacity in the active phase of childhood HPS. Further, abnormality of killing capacity of NK cells may exist even in the remission phase.