Benaroya Research Institute at Virginia Mason, Seattle, WA 98101, USA.
J Immunol. 2011 Oct 1;187(7):3511-20. doi: 10.4049/jimmunol.1003880. Epub 2011 Aug 24.
Low Ag dose promotes induction and persistence of regulatory T cells (Tregs) in mice, yet few studies have addressed the role of Ag dose in the induction of adaptive CD4(+)FOXP3(+) Tregs in humans. To this end, we examined the level of FOXP3 expression in human CD4(+)CD25(-) T cells upon activation with autologous APCs and varying doses of peptide. Ag-specific T cells expressing FOXP3 were identified by flow cytometry using MHC class II tetramer (Tmr). We found an inverse relationship between Ag dose and the frequency of FOXP3(+) cells for both foreign Ag-specific and self Ag-specific T cells. Through studies of FOXP3 locus demethylation and helios expression, we determined that variation in the frequency of Tmr(+)FOXP3(+) T cells was not due to expansion of natural Tregs, but instead, we found that induction, proliferation, and persistence of FOXP3(+) cells was similar in high- and low-dose cultures, whereas proliferation of FOXP3(-) T cells was favored in high Ag dose cultures. The frequency of FOXP3(+) cells positively correlated with suppressive function, indicative of adaptive Treg generation. The frequency of FOXP3(+) cells was maintained with IL-2, but not upon restimulation with Ag. Together, these data suggest that low Ag dose favors the transient generation of human Ag-specific adaptive Tregs over the proliferation of Ag-specific FOXP3(-) effector T cells. These adaptive Tregs could function to reduce ongoing inflammatory responses and promote low-dose tolerance in humans, especially when Ag exposure and tolerance is transient.
低剂量抗原促进调节性 T 细胞（Tregs）在小鼠中的诱导和持续存在，但很少有研究探讨抗原剂量在人类适应性 CD4（+）FOXP3（+）Tregs 的诱导中的作用。为此，我们研究了人类 CD4（+）CD25（-）T 细胞在与自体 APC 和不同剂量肽激活后 FOXP3 的表达水平。通过 MHC 类 II 四聚体（Tmr），使用流式细胞术鉴定表达 FOXP3 的抗原特异性 T 细胞。我们发现，对于外来抗原特异性和自身抗原特异性 T 细胞，抗原剂量与 FOXP3（+）细胞的频率呈反比关系。通过对 FOXP3 基因座去甲基化和 helios 表达的研究，我们确定 Tmr（+）FOXP3（+）T 细胞频率的变化不是由于天然 Tregs 的扩增，而是我们发现，FOXP3（+）细胞的诱导、增殖和持续存在在高剂量和低剂量培养物中是相似的，而 FOXP3（-）T 细胞的增殖则在高抗原剂量培养物中更为有利。FOXP3（+）细胞的频率与抑制功能呈正相关，表明适应性 Treg 的产生。FOXP3（+）细胞的频率在 IL-2 维持，但在再次用抗原刺激时不维持。这些数据表明，低抗原剂量有利于人类抗原特异性适应性 Tregs 的短暂产生，而不是抗原特异性 FOXP3（-）效应 T 细胞的增殖。这些适应性 Tregs 可以发挥作用，减少持续的炎症反应，并在人类中促进低剂量耐受，尤其是在抗原暴露和耐受是短暂的时候。
