The roles of natural killer (NK) cells in shaping the immune system had raised wide interests. Here we intended to explore the regulatory functions of NK cells on CD8+ T cells in severe aplastic anemia (SAA) using human participants and lymphocyte infusion-induced bone marrow failure (BMF) mouse model. In SAA patients, NK cells had over-expressions of NKG2D and NKp46, under-expression of NKG2A and enhanced cytotoxicity. NK cells limited autologous CD8+ T cell immunity in an effector/target ratio manner. The suppression was dependent on the existence of NKG2D. We also observed upregulated MICA expression on activated CD8+ T cells, which were susceptible to NK cell mediated lysis in SAA. Animal model concurred with the data from patients. Infusion of NK cells suppressed the proliferation of CD8+ T cells and decreased IFN-γ production. In conclusion, NK cells served NKG2D-dependent immunoregulatory roles by attenuating autologous CD8+ T cell response in SAA.
Keywords: Autoimmunity; Cytotoxic T cells; Natural killer cells.
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