Barroeta Seijas Amairelys Belen, Simonetti Sonia, Vitale Sara, Runci Daniele, Quinci Angela Caterina, Soriani Alessandra, Criscuoli Mattia, Filippi Irene, Naldini Antonella, Sacchetti Federico Maria, Tarantino Umberto, Oliva Francesco, Piccirilli Eleonora, Santoni Angela, Di Rosa Francesca
Institute of Molecular Biology and Pathology, National Research Council (CNR), c/o Department of Molecular Medicine, University of Rome "Sapienza", Rome, Italy; Department of Molecular Medicine, University of Rome "Sapienza", Rome, Italy.
Department of Molecular Medicine, University of Rome "Sapienza" , Rome , Italy.
Front Immunol. 2017 Feb 16;8:147. doi: 10.3389/fimmu.2017.00147. eCollection 2017.
Stem cell factor (SCF), the ligand of c-kit, is a key cytokine for hematopoiesis. Hematopoietic precursors express c-kit, whereas differentiated cells of hematopoietic lineage are negative for this receptor, with the exception of NK cells, mast cells, and a few others. While it has long been recognized that dendritic cells (DCs) can express c-kit, several questions remain concerning the SCF/c-kit axis in DCs. This is particularly relevant for DCs found in those organs wherein SCF is highly expressed, including the bone marrow (BM). We characterized c-kit expression by conventional DCs (cDCs) from BM and demonstrated a higher proportion of c-kit cells among type 1 cDC subsets (cDC1s) than type 2 cDC subsets (cDC2s) in both humans and mice, whereas similar levels of c-kit expression were observed in cDC1s and cDC2s from mouse spleen. To further study c-kit regulation, DCs were generated with granulocyte-macrophage colony-stimulating factor (GM-CSF) from mouse BM, a widely used protocol. CD11c cells were purified from pooled non-adherent and slightly adherent cells collected after 7 days of culture, thus obtaining highly purified BM-derived DCs (BMdDCs). BMdDCs contained a small fraction of c-kit cells, and by replating them for 2 days with GM-CSF, we obtained a homogeneous population of c-kit CD40 MHCII cells. Not only did BMdDCs express c-kit but they also produced SCF, and both were striking upregulated if GM-CSF was omitted after replating. Furthermore, a small but significant reduction in BMdDC survival was observed upon SCF silencing. Incubation of BMdDCs with SCF did not modulate antigen presentation ability of these cells, nor it did regulate their membrane expression of the chemokine receptor CXCR4. We conclude that the SCF/c-kit-mediated prosurvival circuit may have been overlooked because of the prominent use of GM-CSF in DC cultures , including those human DC cultures destined for the clinics. We speculate that DCs more prominently rely on SCF in some microenvironments, with potential implications for graft-versus-host disease and antitumor immunity.
干细胞因子（SCF）是c-kit的配体，是造血过程中的关键细胞因子。造血前体细胞表达c-kit，而造血谱系的分化细胞除自然杀伤细胞、肥大细胞等少数细胞外，该受体呈阴性。虽然长期以来人们都认识到树突状细胞（DC）可以表达c-kit，但关于DC中SCF/c-kit轴仍存在一些问题。这对于在SCF高度表达的器官（包括骨髓（BM））中发现的DC尤为重要。我们对来自骨髓的传统DC（cDC）的c-kit表达进行了表征，并证明在人类和小鼠中，1型cDC亚群（cDC1）中c-kit阳性细胞的比例高于2型cDC亚群（cDC2），而在小鼠脾脏的cDC1和cDC2中观察到相似水平的c-kit表达。为了进一步研究c-kit的调节，我们使用粒细胞-巨噬细胞集落刺激因子（GM-CSF）从小鼠骨髓中生成DC，这是一种广泛使用的方案。从培养7天后收集的非贴壁和轻度贴壁细胞池中纯化CD11c阳性细胞，从而获得高度纯化的骨髓来源的DC（BMdDC）。BMdDC中含有一小部分c-kit阳性细胞，通过用GM-CSF将它们再培养2天，我们获得了均一的c-kit阳性CD40 MHCII阳性细胞群体。BMdDC不仅表达c-kit，还产生SCF，并且如果在再培养后省略GM-CSF，两者都会显著上调。此外，在SCF沉默后观察到BMdDC的存活率有小幅但显著的降低。用SCF孵育BMdDC不会调节这些细胞的抗原呈递能力，也不会调节它们趋化因子受体CXCR4的膜表达。我们得出结论，由于在DC培养中，包括那些用于临床的人类DC培养中广泛使用GM-CSF，SCF/c-kit介导的促存活回路可能被忽视了。我们推测，在某些微环境中，DC更显著地依赖SCF，这对移植物抗宿主病和抗肿瘤免疫可能有潜在影响。
