Alamino Vanina Alejandra, Montesinos María Del Mar, Soler María Florencia, Giusiano Lucila, Gigena Nicolás, Fozzatti Laura, Maller Sebastián Matías, Méndez-Huergo Santiago Patricio, Rabinovich Gabriel Adrián, Pellizas Claudia Gabriella
Centro de Investigaciones en Bioquímica Clínica e Inmunología (CIBICI-CONICET) and Departamento de Bioquímica Clínica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina.
Laboratorio de Inmunopatología, Instituto de Biología y Medicina Experimental (IBYME-CONICET) and Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina.
Cell Physiol Biochem. 2019;52(2):354-367. doi: 10.33594/000000025. Epub 2019 Feb 28.
BACKGROUND/AIMS: Although a cross-talk between immune and endocrine systems has been well established, the precise pathways by which these signals co-regulate pro- and antiinflammatory responses on antigen-presenting cells remain poorly understood. In this work we investigated the mechanisms by which triiodothyronine (T3) controls T cell activity via dendritic cell (DC) modulation.
DCs from wild-type (WT) and IL-6-deficient mice were pulsed with T3. Cytokine production and programmed death protein ligands (PD-L) 1 and 2 expression were assayed by flow cytometry and ELISA. Interferon-regulatory factor-4 (IRF4) expression was evaluated by RT-qPCR and flow cytometry. The ability of DCs to stimulate allogenic splenocytes was assessed in a mixed lymphocyte reaction and the different profile markers were analyzed by flow cytometry and ELISA. For in vivo experiments, DCs treated with ovalbumin and T3 were injected into OTII mice. Proliferation, cytokine production, frequency of FoxP3 regulatory T (Treg) cells and PD-1 cells were determined by MTT assay, ELISA and flow cytometry, respectively.
T3 endows DCs with pro-inflammatory potential capable of generating IL-17-dominant responses and down-modulating expression of PD-L1 and 2. T3-stimulated WT-DCs increased the proportion of IL-17-producing splenocytes, an effect which was eliminated when splenocytes were incubated with T3-treated DCs derived from IL-6-deficient mice. Enhanced IL-17 expression was recorded in both, CD4 and CD4 populations and involved the IRF-4 pathway. Particularly, γδ-T cells but not natural killer (NK), NKT, B lymphocytes nor CD8 T cells were the major source of IL-17-production from CD4 cells. Moreover, T3-conditioned DCs promoted a decrease of the FoxP3 Treg population. Furthermore, T3 down-modulated PD-1 expression on CD4 cells thereby limiting inhibitory signals driven by this co-inhibitory pathway. Thus, T3 acts at the DC level to drive proinflammatory responses in vitro. Accordingly, we found that T3 induces IL-17 and IFNγ-dominant antigen-specific responses in vivo.
These results emphasize the relevance of T3 as an additional immune-endocrine checkpoint and a novel therapeutic target to modulate IL-17-mediated pro-inflammatory responses.
背景/目的：尽管免疫系统与内分泌系统之间的相互作用已得到充分证实，但这些信号共同调节抗原呈递细胞上促炎和抗炎反应的确切途径仍知之甚少。在本研究中，我们探究了三碘甲状腺原氨酸（T3）通过调节树突状细胞（DC）来控制T细胞活性的机制。
用T3刺激野生型（WT）和白细胞介素6（IL-6）缺陷型小鼠的DC。通过流式细胞术和酶联免疫吸附测定（ELISA）检测细胞因子的产生以及程序性死亡蛋白配体（PD-L）1和2的表达。通过逆转录定量聚合酶链反应（RT-qPCR）和流式细胞术评估干扰素调节因子4（IRF4）的表达。在混合淋巴细胞反应中评估DC刺激同种异体脾细胞的能力，并通过流式细胞术和ELISA分析不同的特征性标志物。对于体内实验，将用卵清蛋白和T3处理的DC注射到OTII小鼠体内。分别通过MTT法、ELISA和流式细胞术测定增殖、细胞因子产生、叉头框蛋白P3调节性T（Treg）细胞和程序性死亡蛋白1（PD-1）细胞的频率。
T3赋予DC促炎潜能，能够产生以白细胞介素17（IL-17）为主导的反应，并下调PD-L1和2的表达。T3刺激的WT-DC增加了产生IL-17的脾细胞比例，当脾细胞与源自IL-6缺陷型小鼠的经T3处理的DC孵育时，这种效应消失。在CD4和CD4细胞群体中均记录到IL-17表达增强，且涉及IRF-4途径。特别是，γδ-T细胞而非自然杀伤（NK）细胞、自然杀伤T（NKT）细胞、B淋巴细胞或CD8 T细胞是CD4细胞产生IL-17的主要来源。此外，经T3处理的DC促进了FoxP3 Treg细胞群体的减少。此外，T3下调了CD4细胞上PD-1的表达，从而限制了由该共抑制途径驱动的抑制信号。因此，T3在DC水平发挥作用，在体外驱动促炎反应。相应地，我们发现在体内T3诱导以IL-17和干扰素γ（IFNγ）为主导的抗原特异性反应。
这些结果强调了T3作为额外的免疫-内分泌检查点以及调节IL-17介导的促炎反应的新型治疗靶点的重要性。
