Background

Immunosuppressive-drugs are needed after solid organ transplantation to prevent allograft rejection but induce severe side effects. Understanding the alloimmune response is critical to modulate it and to achieve graft operational tolerance. The role of regulatory T cells and tolerogenic dendritic cells (Tol-DCs) is undoubtedly essential in tolerance induction. Tacrolimus is considered as the cornerstone of immunosuppression in solid organ transplantation. mTOR inhibitor such as rapamycin are thought to induce tolerance and are used as anticancer drugs in several cancers. The aim of this study was to better understand the effect of these immunosuppressive drugs on the differentiation, maturation and function of human monocyte derived dendritic cells (DCs).

Material and methods

DCs were differentiated from monocytes of healthy donors with either rapamycin (Rapa-DCs) or tacrolimus (Tac-DCs). The phenotype was evaluated by flow cytometry analysis. The production of pro- and anti-inflammatory cytokines was assessed by ELISA. The mRNA expression level of IDO and PD-L1 was assessed by RTqPCR. Mixed leukocytes reactions were performed to analyse suppressive activity of DCs.

Results

Rapa-DC were characterised by a lower expression of the co-stimulatory molecules and CD83 than control-DCs (CTR-DC) (p < 0.05). In contrast, tacrolimus had no effect on the expression of surface markers compared to CTR-DCs. Rapamycin reduced both IL-12 and IL-10 secretions (p < 0.05). Rapa-DCs had a suppressive effect on CD4⁺ allogenic T cells compared to CTR-DCs (p < 0.05). However, neither Rapa-DCs nor Tac-DCs favoured the emergence of a CD4⁺CD25^highFoxp3⁺ population compared to CTR-DCs. Surprisingly, Rapa-DCs had a reduced expression of IDO and PD-L1 compared to Tac-DCs and CTR-DCs.

Conclusion

Rapa-DCs exhibit an incomplete phenotypic tolerogenic profile. To our knowledge this is the first paper showing a reduction of expression of pro-tolerogenic enzyme IDO in DCs. Tacrolimus does not change the phenotypical or functional characteristics of moDCs.

中文翻译：

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雷帕霉素和他克莫司对单核细胞源性树突状细胞表型和功能的调节作用

背景

实体器官移植后需要免疫抑制药物来预防同种异体移植排斥，但会引起严重的副作用。了解同种免疫反应对于调节它和实现移植物操作耐受性至关重要。调节性 T 细胞和致耐受性树突状细胞 (Tol-DCs) 的作用在耐受性诱导中无疑是必不可少的。他克莫司被认为是实体器官移植中免疫抑制的基石。mTOR 抑制剂如雷帕霉素被认为可诱导耐受，并在几种癌症中用作抗癌药物。本研究的目的是更好地了解这些免疫抑制药物对人单核细胞衍生树突状细胞 (DC) 分化、成熟和功能的影响。

材料与方法

用雷帕霉素 (Rapa-DCs) 或他克莫司 (Tac-DCs) 将 DCs 从健康供体的单核细胞中分化出来。通过流式细胞术分析评估表型。通过ELISA评估促炎和抗炎细胞因子的产生。通过 RTqPCR 评估 IDO 和 PD-L1 的 mRNA 表达水平。进行混合白细胞反应以分析 DC 的抑制活性。

结果

Rapa-DC 的特征是共刺激分子和 CD83 的表达低于对照-DC (CTR-DC) (p < 0.05)。相反，与 CTR-DC 相比，他克莫司对表面标志物的表达没有影响。雷帕霉素减少了 IL-12 和 IL-10 的分泌（p < 0.05）。与 CTR-DC 相比， Rapa-DC 对 CD4 ⁺同种异体 T 细胞具有抑制作用（p < 0.05）。然而，与 CTR-DC 相比，Rapa-DC 和 Tac-DC 都不赞成出现 CD4 ⁺ CD25^高Foxp3 ^+群体。令人惊讶的是，与 Tac-DC 和 CTR-DC 相比，Rapa-DC 的 IDO 和 PD-L1 表达降低。

结论

Rapa-DC 表现出不完整的表型耐受性特征。据我们所知，这是第一篇显示 DCs 中促耐受酶 IDO 表达减少的论文。他克莫司不会改变 moDCs 的表型或功能特征。