DataSheet_1_Analysis of Iron and Iron-Interacting Protein Dynamics During T-Cell Activation.pdf

Recent findings have shown that iron is a powerful regulator of immune responses, which is of broad importance because iron deficiency is highly prevalent worldwide. However, the underlying reasons of why iron is needed by lymphocytes remain unclear. Using a combination of mathematical modelling, bioinformatic analysis and experimental work, we studied how iron influences T-cells. We identified iron-interacting proteins in CD4+ and CD8+ T-cell proteomes that were differentially expressed during activation, suggesting that pathways enriched with such proteins, including histone demethylation, may be impaired by iron deficiency. Consistent with this, iron-starved Th17 cells showed elevated expression of the repressive histone mark H3K27me3 and displayed reduced RORγt and IL-17a, highlighting a previously unappreciated role for iron in T-cell differentiation. Quantitatively, we estimated T-cell iron content and calculated that T-cell iron demand rapidly and substantially increases after activation. We modelled that these increased requirements will not be met during clinically defined iron deficiency, indicating that normalizing serum iron may benefit adaptive immunity. Conversely, modelling predicted that excess serum iron would not enhance CD8+ T-cell responses, which we confirmed by immunising inducible hepcidin knock-out mice that have very high serum iron concentrations. Therefore, iron deficiency impairs multiple aspects of T-cell responses, while iron overload likely has milder effects.

近期研究表明，铁（iron）是免疫应答的强效调控因子，该发现具有广泛的研究意义——鉴于缺铁在全球范围内均具有高患病率。然而，淋巴细胞依赖铁的内在机制尚未明确。本研究结合数学建模（mathematical modelling）、生物信息学分析（bioinformatic analysis）与实验技术，探究铁对T细胞（T-cell）的调控效应。我们在活化过程中呈差异表达的CD4+ T细胞（CD4+ T-cell）与CD8+ T细胞（CD8+ T-cell）蛋白质组（proteome）中，鉴定出铁互作蛋白；这提示富含此类蛋白的通路（包括组蛋白去甲基化（histone demethylation）通路）可能因缺铁而功能受损。与此一致，铁饥饿状态下的Th17细胞（Th17 cell）中，抑制性组蛋白标记H3K27me3的表达水平升高，而RORγt与IL-17a的表达水平降低，这凸显了铁在T细胞分化中此前未被认知的调控作用。在定量层面，我们估算了T细胞的铁含量，并测算得出：T细胞活化后，其铁需求会快速且显著上升。我们通过建模发现，临床确诊的缺铁状态无法满足T细胞新增的铁需求，这提示将血清铁（serum iron）水平恢复至正常范围或可改善适应性免疫（adaptive immunity）。与之相反，建模预测血清铁过量并不会增强CD8+ T细胞的应答反应，该结论通过对血清铁水平极高的诱导型铁调素敲除小鼠（inducible hepcidin knock-out mice）进行免疫接种得到了验证。综上，缺铁会损害T细胞应答的多个环节，而铁过载（iron overload）对T细胞的影响则相对更为温和。