Department of Hematology and Oncology, Winship Cancer Institute, Emory University, Atlanta, GA 30322.
J Immunol. 2014 Feb 15;192(4):1491-501. doi: 10.4049/jimmunol.1301828. Epub 2014 Jan 8.
Human bone marrow-derived mesenchymal stromal cells (MSCs) inhibit proliferation of activated T cells, and IFN-γ plays an important role in this process. This IFN-γ-licensed veto property is IDO-dependent. To further decipher the mechanistic underpinnings of MSC veto function on T cells, we investigated the effect of MSCs and IFN-γ-licensed MSCs on T cell effector function as assayed by cytokine secretion of T cells. Although MSCs and IFN-γ-licensed MSCs inhibit T cell proliferation, only IFN-γ-licensed MSCs significantly inhibit Th1 cytokine (IFN-γ, TNF-α, and IL-2) production by T cells. Additionally, IFN-γ-licensed MSCs inhibit T cell degranulation as well as single, double, and triple cytokine-producing T cells. Although IFN-γ-licensed MSCs upregulate their IDO activity, we found that MSC IDO catalytic function is dispensable with regard to MSC-driven inhibition of T cell effector function. Novel flow cytometry based functional screening of MSC-expressed, IFN-γ-licensed inhibitory molecules identified B7H1 and B7DC/PD1 pathways as essential effectors in blocking T cell function. Small interfering RNA-mediated blocking of B7H1 and B7DC reverses the inhibitory potential of IFN-γ-licensed MSCs on T cell effector function. Mechanistic analysis revealed that clustering of MHC and coinhibitory molecules are indispensable for the inhibitory effect of IFN-γ MSCs. Although exogenous IL-2 reverses B7H1-Ig-mediated inhibition of T cell proliferation, it does not affect the veto function of IFN-γ MSCs on both T cell proliferation and effector function. Our results reveal a new immunosuppressive property of IFN-γ-licensed MSCs that inhibits T cell effector function independent of IDO but through the ligands for PD1.
人骨髓间充质基质细胞（MSCs）抑制活化 T 细胞的增殖，IFN-γ 在这个过程中起着重要作用。这种 IFN-γ 许可的否决特性依赖于 IDO。为了进一步阐明 MSC 对 T 细胞否决功能的机制基础，我们研究了 MSCs 和 IFN-γ 许可的 MSCs 对 T 细胞效应功能的影响，方法是检测 T 细胞的细胞因子分泌。虽然 MSCs 和 IFN-γ 许可的 MSCs 抑制 T 细胞增殖，但只有 IFN-γ 许可的 MSCs 显著抑制 Th1 细胞因子（IFN-γ、TNF-α 和 IL-2）的产生。此外，IFN-γ 许可的 MSCs 抑制 T 细胞脱颗粒以及单、双和三细胞因子产生的 T 细胞。虽然 IFN-γ 许可的 MSCs 上调其 IDO 活性，但我们发现 MSC IDO 催化功能对于 MSC 驱动的 T 细胞效应功能抑制是可有可无的。基于流式细胞术的 MSC 表达的 IFN-γ 许可的抑制性分子的新型功能筛选，确定了 B7H1 和 B7DC/PD1 途径作为阻断 T 细胞功能的必需效应物。小干扰 RNA 介导的 B7H1 和 B7DC 阻断逆转了 IFN-γ 许可的 MSCs 对 T 细胞效应功能的抑制潜力。机制分析表明，MHC 和共抑制分子的聚类对于 IFN-γ MSCs 的抑制作用是必不可少的。虽然外源性 IL-2 逆转了 B7H1-Ig 对 T 细胞增殖的抑制作用，但它不影响 IFN-γ MSCs 对 T 细胞增殖和效应功能的否决功能。我们的结果揭示了 IFN-γ 许可的 MSCs 的一种新的免疫抑制特性，该特性通过 PD1 的配体独立于 IDO 抑制 T 细胞效应功能。
