Kremer Kimberly N, Kumar Ashok, Hedin Karen E
Department of Immunology, Mayo Clinic College of Medicine, Mayo Clinic, Rochester, MN 55905, USA.
J Immunol. 2007 Feb 1;178(3):1581-8. doi: 10.4049/jimmunol.178.3.1581.
Costimulation by the chemokine, stromal cell-derived factor-1 (SDF-1)/CXCL12, has been shown to increase the amount of IL-10 secreted by TCR-stimulated human T cells; however, the molecular mechanisms of this response are unknown. Knowledge of this signaling pathway may be useful because extensive evidence indicates that deficient IL-10 secretion promotes autoimmunity. The human IL-10 locus is highly polymorphic. We report in this study that SDF-1 costimulates IL-10 secretion from T cells containing all three of the most common human IL-10 promoter haplotypes that are identified by single-nucleotide polymorphisms at -1082, -819, and -592 bp (numbering is relative to the transcription start site). We further show that SDF-1 primarily costimulates IL-10 secretion by a diverse population of CD45RA(-) ("memory") phenotype T cells that includes cells expressing the presumed regulatory T cell marker, Foxp3. To address the molecular mechanisms of this response, we showed that SDF-1 costimulates the transcriptional activities in normal human T cells of reporter plasmids containing 1.1 kb of all three of the common IL-10 promoter haplotypes. IL-10 promoter activity was ablated by mutating two nonpolymorphic binding sites for the AP-1 transcription factor, and chromatin immunoprecipitation assays of primary human T cells revealed that SDF-1 costimulation enhances AP-1 binding to both of these sites. Together, these results delineate the molecular mechanisms responsible for SDF-1 costimulation of T cell IL-10 secretion. Because it is preserved among several human haplotypes and in diverse T cell populations including Foxp3(+) T cells, this pathway of IL-10 regulation may represent a key mechanism for modulating expression of this important immunoregulatory cytokine.
趋化因子基质细胞衍生因子-1（SDF-1）/CXCL12的共刺激作用已被证明可增加经TCR刺激的人T细胞分泌的IL-10量；然而，这种反应的分子机制尚不清楚。了解这一信号通路可能会有所帮助，因为大量证据表明IL-10分泌不足会促进自身免疫。人IL-10基因座具有高度多态性。我们在本研究中报告，SDF-1对含有通过-1082、-819和-592 bp处的单核苷酸多态性鉴定的所有三种最常见人IL-10启动子单倍型的T细胞分泌IL-10具有共刺激作用（编号相对于转录起始位点）。我们进一步表明，SDF-1主要通过多种CD45RA(-)（“记忆”）表型T细胞共刺激IL-10分泌，这些T细胞包括表达推测的调节性T细胞标志物Foxp3的细胞。为了探究这种反应的分子机制，我们表明SDF-1对含有所有三种常见IL-10启动子单倍型1.1 kb的报告质粒在正常人T细胞中的转录活性具有共刺激作用。通过突变AP-1转录因子的两个非多态性结合位点可消除IL-10启动子活性，对原代人T细胞进行的染色质免疫沉淀分析表明，SDF-1共刺激增强了AP-1与这两个位点的结合。这些结果共同描绘了负责SDF-1共刺激T细胞分泌IL-10的分子机制。由于它在几种人类单倍型以及包括Foxp3(+) T细胞在内的多种T细胞群体中都存在，这种IL-10调节途径可能代表了调节这种重要免疫调节细胞因子表达的关键机制。
