Interleukin-7 expression and its effect on natural killer cells in patients with multiple sclerosis

Decreased NK cell numbers and impairment of NK cell function are reported in patients with multiple sclerosis (MS). Interleukin-7 (IL-7) is a member of the common gamma-chain (γc) cytokine superfamily that has well documented roles in lymphocyte development and homeostasis. The interleukin-7 receptor α chain (IL-7Rα) gene was identified as a top non-major histocompatibility complex-linked risk locus for MS. The objective of this study was to test biological function of IL-7/IL-7Rα on NK cells in MS patients. We observed markedly lower IL-7 levels in MS sera, and relatively higher IL-7Rα expression in NK cells of MS. Upon IL-7 stimulation, IL-7Rα on NK cells from MS patients was significantly down-regulated compared with healthy controls (HCs). IL-7 induced a higher increase of IFN-γ production in CD56(bright) NK cells and a pronounced enhancement of cytotoxicity in NK cells from MS. IL-7 did not impact the proliferation of NK cells differently in MS and HC. In contrast, IL-7 promoted a higher survival of CD56(bright) NK cells in MS and inhibited their apoptosis by increasing Bcl-2 expression, but had no effect on CD56(dim) NK cell survival in MS. In conclusion, MS patients have lower serum IL-7 and a higher membrane IL-7Rα expression on CD56(bright) NK cells. The skew at the IL-7 and IL-7Rα level influences functional responsiveness of NK cells in MS.