York Michael R, Nagai Taro, Mangini Alyson J, Lemaire Raphaël, van Seventer Jean Maguire, Lafyatis Robert
Boston University Medical Center, Boston, Massachusetts 02118, USA.
Arthritis Rheum. 2007 Mar;56(3):1010-20. doi: 10.1002/art.22382.
Microarray analyses of peripheral blood leukocytes have shown that patients with systemic lupus erythematosus express increased levels of type I interferon (IFN)-regulated genes. In this study we examined gene expression by peripheral blood mononuclear cells (PBMCs) from patients with systemic sclerosis (SSc) to better understand the dysregulation of the immune system in this disease.
PBMC gene expression was analyzed by microarray and confirmed by real-time polymerase chain reaction (PCR). Surface protein expression of Siglec-1 was analyzed by flow cytometry in PBMCs from healthy control subjects and patients with SSc, and in control PBMCs that were cultured in vitro with Toll-like receptor (TLR) agonists.
SSc patients showed increased expression of a cluster of IFN-regulated genes, including Siglec-1 (CD169, sialoadhesin). This result was verified and extended by real-time PCR, showing that a subset of the SSc patients expressed strikingly increased levels of Siglec-1 messenger RNA (mRNA). Flow cytometry of PBMCs from SSc patients and healthy controls showed increased Siglec-1 surface protein expression, which was restricted to CD14+ monocytes. In vitro studies showed that type I IFN and certain TLR agonists, including TLR-7 and TLR-9, induced Siglec-1 mRNA and protein expression. Moreover, TLR induction of surface Siglec-1 was shown to be type I IFN-dependent. Increased numbers of Siglec-1+ cells were observed by immunohistochemistry in the skin of SSc patients compared with healthy controls.
Increased expression of Siglec-1 in circulating SSc monocytes and tissue macrophages suggests that type I IFN-mediated activation of monocytes occurs in SSc, possibly through TLR activation of IFN secretion. These observations indicate a potential role for type I IFN-activated monocyte/macrophages in the pathogenesis of SSc.
外周血白细胞的微阵列分析表明，系统性红斑狼疮患者中I型干扰素（IFN）调节基因的表达水平升高。在本研究中，我们检测了系统性硬化症（SSc）患者外周血单个核细胞（PBMC）的基因表达，以更好地了解该疾病中免疫系统的失调情况。
通过微阵列分析PBMC基因表达，并通过实时聚合酶链反应（PCR）进行验证。采用流式细胞术分析健康对照受试者和SSc患者的PBMC中Siglec-1的表面蛋白表达，以及在体外与 Toll样受体（TLR）激动剂培养的对照PBMC中的表达。
SSc患者显示出一组IFN调节基因的表达增加，包括Siglec-1（CD169，唾液酸粘附素）。实时PCR验证并扩展了这一结果，表明一部分SSc患者的Siglec-1信使核糖核酸（mRNA）水平显著升高。SSc患者和健康对照的PBMC流式细胞术显示Siglec-1表面蛋白表达增加，且仅限于CD14+单核细胞。体外研究表明，I型IFN和某些TLR激动剂，包括TLR-7和TLR-9，可诱导Siglec-1 mRNA和蛋白表达。此外，TLR诱导的表面Siglec-1表达是I型IFN依赖性的。与健康对照相比，通过免疫组织化学观察到SSc患者皮肤中Siglec-1+细胞数量增加。
循环中的SSc单核细胞和组织巨噬细胞中Siglec-1表达增加表明，SSc中可能通过TLR激活IFN分泌，发生了I型IFN介导的单核细胞活化。这些观察结果表明I型IFN激活的单核细胞/巨噬细胞在SSc发病机制中具有潜在作用。
