Myers Lara, Croft Michael, Kwon Byoung S, Mittler Robert S, Vella Anthony T
Division of Immunology, University of Connecticut Health Center, Farmington, CT 06032, USA.
J Immunol. 2005 Jun 15;174(12):7625-32. doi: 10.4049/jimmunol.174.12.7625.
We identified a murine peptide-specific CD8 T regulatory cell population able to suppress responding CD4 T cells. Immunization with OVA, poly(I:C), and anti-4-1BB generated a population of SIINFEKL-specific CD8 T regulatory cells that profoundly inhibited peptide-responding CD4 T cells from cellular division. The mechanism of suppression required IFN-gamma, but IFN-gamma alone was not sufficient to suppress the responding CD4 T cells. The data show that CD8 T regulatory cells were unable to suppress unless they engaged IFN-gamma. Furthermore, even in the absence of recall with peptide, the CD8 T regulatory cells suppressed CD4 responses as long as IFN-gamma was present. To examine the effector mechanism of suppression, we showed that neutralizing TGF-beta inhibited suppression because inclusion of anti-TGF-beta rescued the proliferative capacity of the responding cells. TGF-beta-based suppression was dependent completely upon the CD8 T regulatory cells being capable of binding IFN-gamma. This was the case, although peptide recall of primed IFN-gamma (-/-) or IFN-gammaR(-/-) CD8 T cells up-regulated pro-TGF-beta protein as measured by surface latency-associated peptide expression but yet were unable to suppress. Finally, we asked whether the CD8 T regulatory cells were exposed to active TGF-beta in vivo and showed that only wild-type CD8 T regulatory cells expressed the TGF-beta-dependent biomarker CD103, suggesting that latency-associated peptide expression is not always congruent with elaboration of active TGF-beta. These data define a novel mechanism whereby IFN-gamma directly stimulates CD8 T regulatory cells to elaborate TGF-beta-based suppression. Ultimately, this mechanism may permit regulation of pathogenic Th1 responses by CD8 T regulatory cells.
我们鉴定出了一个能够抑制反应性CD4 T细胞的小鼠肽特异性CD8 T调节细胞群体。用卵清蛋白（OVA）、聚肌胞苷酸（poly(I:C)）和抗4-1BB进行免疫接种，产生了一群SIINFEKL特异性CD8 T调节细胞，这些细胞能显著抑制肽反应性CD4 T细胞的细胞分裂。抑制机制需要γ干扰素（IFN-γ），但仅IFN-γ不足以抑制反应性CD4 T细胞。数据表明，CD8 T调节细胞除非与IFN-γ结合，否则无法发挥抑制作用。此外，即使没有肽的再次刺激，只要有IFN-γ存在，CD8 T调节细胞就能抑制CD4反应。为了研究抑制的效应机制，我们发现中和转化生长因子β（TGF-β）可抑制抑制作用，因为加入抗TGF-β可恢复反应细胞的增殖能力。基于TGF-β的抑制作用完全依赖于CD8 T调节细胞能够结合IFN-γ。尽管通过表面潜伏期相关肽表达检测发现，对经IFN-γ预处理的IFN-γ基因敲除（-/-）或IFN-γ受体基因敲除（-/-）的CD8 T细胞进行肽再次刺激会上调前TGF-β蛋白，但它们仍无法发挥抑制作用，情况依然如此。最后，我们探究了CD8 T调节细胞在体内是否接触到活性TGF-β，并发现只有野生型CD8 T调节细胞表达TGF-β依赖性生物标志物CD103，这表明潜伏期相关肽表达并不总是与活性TGF-β的产生一致。这些数据定义了一种新机制，即IFN-γ直接刺激CD8 T调节细胞产生基于TGF-β的抑制作用。最终，这种机制可能使CD8 T调节细胞能够调控致病性Th1反应。
