Echinococcus multilocularis induces surface high expression of inhibitory killer immunoglobulin-like receptor on natural killer cells.

Alveolar echinococcosis (AE) is a malignant and fatal parasitic disease caused by the larvae of Echinococcus multilocularis (E. multilocularis), which inhibits the activity and proliferation of natural killer (NK) cells. In this study, the functional alteration of hepatic NK cells and their related molecules were studied. The AE-infected patient's tissue was fixed with formalin, embedded in paraffin, and stained with Masson's trichrome or hematoxylin and eosin (H&E). Single cells from AE-infected patient or E. multilocularis-infected mice were blocked with Fc-receptor (FcR), and stained with monoclonal antibodies, including CD16, CD56, CD3, KIR2DL1, granzyme B, perforin, Interferon gamma (IFN-γ), and tumor necrosis factor-α (TNFα) or isotype control, to measure molecules and cytokines of NK cells and analyzed by flow cytometry. The Sirius red staining was used to quantitate hepatic fibrosis by calculating quantitative collagen deposition. AE can adjust both the number of hepatic CD56+ NK cells and its KIR2DL1 expression processes. Moreover, the overexpression of KIR2DL1 in NK cells could downregulate the functioning of immune cells in the liver area close to parasitic lesions. The number and dysfunction of NK cells in E. multilocularis infection could be related to the molecule dynamics of cell surface inhibitory receptor Ly49A, leading to hepatic damage and progression of fibrosis. This study illustrated significant increase in hepatic fibrogenesis and apparent upregulation of hepatic CD56+ NK cell population and its KIR2DL1 expression in AE-infected patients. This opposite variation might be related to the impaired NK cells functioning, such as granzyme B, IFN-γ, and TNF-α secretion. In addition, the cell surface inhibitory receptor Ly49A was related to the intracellular cytokine secretion functions of NK cells.