Yu H, Fehniger T A, Fuchshuber P, Thiel K S, Vivier E, Carson W E, Caligiuri M A
Divisions of Human Cancer Genetics, Hematology/Oncology, and Surgical Oncology, Department of Pathology, and the Comprehensive Cancer Center of The Ohio State University, Columbus, OH.
Blood. 1998 Nov 15;92(10):3647-57.
Interleukin-15 (IL-15) is produced by human bone marrow (BM) stromal cells and can induce CD34(+) hematopoietic progenitor cells (HPCs) to differentiate into CD56(+)CD3(-) natural killer (NK) cells in the absence of stromal cells. IL-15 mediates its effects by signaling through the beta and gammac chains of the IL-2/15 receptor (R). The c-kit ligand (KL), also produced by stromal cells, enhances the expansion of NK cells from CD34(+) HPCs in the presence of IL-15, but alone has no ability to differentiate NK cells. Mice deficient in KL do not appear to have a quantitative deficiency in NK cells, suggesting that other stromal cell factors may contribute to NK cell expansion. Flt3 ligand (FL) is also produced by BM stromal cells and has homology with KL. Furthermore, mice with a targeted disruption of the FL gene have reduced numbers of NK cells. We evaluated here the effects of FL on human NK cell development and expansion from CD34(+) HPCs. Like KL, FL significantly enhanced the expansion of NK cells from CD34(+) HPCs in the presence of IL-15, compared with IL-15 alone. However, FL alone had no effect on NK cell differentiation. We therefore explored the mechanism by which FL promotes IL-15-mediated NK cell development. FL was found to induce IL-2/15Rbeta (CD122) expression on CD34(bright) HPCs. The CD34(bright) CD122(+) cell coexpressed CD38, but lacked expression of CD7, CD56, NK cell receptors (NKRs), or cytotoxic activity in the absence of IL-15. Using limiting dilution analysis in the presence of IL-15 alone, we demonstrated that the FL-induced CD34(bright)CD122(+) HPCs had an NK cell precursor frequency 20- to 60-fold higher than the CD34(dim/neg)CD122(-) HPCs and 65- to 235-fold higher than fresh CD34(+) HPCs. KL had similar effects as FL, but induced a significantly lower percentage of CD34(bright)CD122(+) cells (P </=.01). Both FL and KL also increased IL-15R transcript in CD34(+) HPCs. Culture of CD34(+) HPCs in FL or KL, followed by culture in IL-15 alone, induced expression of both C-type lectin and Ig-superfamily NKRs on CD56(+) cells. These data collectively support a role for FL in early human NK cell development. FL or KL generate a unique CD34(bright) CD122(+)CD38(+) human NK cell intermediate from CD34(+) HPCs that lacks NK features yet is IL-15-responsive. IL-15 is then required for the induction of CD56 and NKRs, LGL morphology, cytotoxic activity, and the ability to produce abundant cytokines and chemokines.
白细胞介素-15（IL-15）由人骨髓（BM）基质细胞产生，在无基质细胞的情况下，可诱导CD34(+)造血祖细胞（HPCs）分化为CD56(+)CD3(-)自然杀伤（NK）细胞。IL-15通过IL-2/15受体（R）的β链和γc链信号传导介导其作用。同样由基质细胞产生的c-kit配体（KL），在IL-15存在的情况下可增强CD34(+) HPCs来源的NK细胞的扩增，但单独使用时无分化NK细胞的能力。KL缺陷的小鼠似乎不存在NK细胞数量上的缺陷，这表明其他基质细胞因子可能有助于NK细胞的扩增。Flt3配体（FL）也由BM基质细胞产生，与KL具有同源性。此外，FL基因靶向破坏的小鼠NK细胞数量减少。我们在此评估了FL对人NK细胞从CD34(+) HPCs发育和扩增的影响。与KL一样，与单独的IL-15相比，FL在IL-15存在的情况下显著增强了CD34(+) HPCs来源的NK细胞的扩增。然而，单独的FL对NK细胞分化无影响。因此，我们探究了FL促进IL-15介导的NK细胞发育的机制。发现FL可诱导CD34(bright) HPCs上IL-2/15Rβ（CD122）的表达。在无IL-15的情况下，CD34(bright) CD122(+)细胞共表达CD38，但缺乏CD7、CD56、NK细胞受体（NKRs）的表达或细胞毒性活性。在仅存在IL-15的情况下进行有限稀释分析，我们证明FL诱导的CD34(bright)CD122(+) HPCs的NK细胞前体频率比CD34(dim/neg)CD122(-) HPCs高20至60倍，比新鲜CD34(+) HPCs高65至235倍。KL具有与FL类似的作用，但诱导的CD34(bright)CD
