ChIP Seq of influenza specific primary, memory and secondary CD4+ T cells [In Vivo]

Immune responses to infection involve a careful balance: too weak a response allows pathogen replication; too strong risks immunopathology. The immunoregulatory cytokine IL-10 is a key factor in this balance, but the impact of IL-10 is context-dependent and current understanding of the factors that regulate IL-10 is incomplete. In this study, we demonstrated that the infection induced cytokine IL-27 promotes IL-10 expression in CD4+ T cells by directing epigenetic changes in H3K4me3, H3K27me3, H3K4me1 and H3K27Ac modifications at the Il10 locus. We showed that primary activation of antigen-specific CD4+ T cells, in the context of murine influenza infection, led to the long-term remodelling of the epigenetic landscape at both the Il10 promoter and a distinct active enhancer element ~ 25 kb upstream of the TSS. Intact IL-27 signalling was an essential requirement for these persistent epigenetic changes in memory CD4+ Tcells. We identified CREB1 as a transcription factor binding the Il10 active enhancer, and we showed that the ability of IL-27 to promote IL-10 expression was dependent on the histone acetyl transferase activity of the CREB1 complex member, p300. Together our data provide mechanistic insight into the action of IL-27 in regulating an immune response. We suggest that infection-induced cytokine signals direct epigenetic changes that moderate cytokine output in response to T cell receptor stimulation, regulating immune activity at sites of infection. Overall design: 20 samples; naïve B6, primary (Day 10), memory (Day 35), secondary (Day 6)

机体针对感染的免疫应答需维持精细平衡：应答过弱将允许病原体增殖，应答过强则存在免疫病理风险。免疫调节性细胞因子白细胞介素10（IL-10）是维持该平衡的关键因子，但其功能具有情境依赖性，目前学界对调控IL-10的相关因素的认知仍不全面。本研究证实，感染诱导产生的细胞因子白细胞介素27（IL-27）可通过调控Il10基因座上H3K4me3、H3K27me3、H3K4me1及H3K27Ac等组蛋白修饰的表观遗传变化，促进CD4阳性T细胞（CD4+ T cells）中IL-10的表达。研究显示，在小鼠流感感染模型中，抗原特异性CD4阳性T细胞的初次活化可促使Il10基因启动子及转录起始位点（TSS, Transcription Start Site）上游约25 kb处的特异性活性增强子区域的表观遗传景观发生长期重塑。完整的IL-27信号通路是记忆性CD4阳性T细胞中这类持续性表观遗传变化的必需条件。本研究鉴定出结合Il10基因活性增强子的转录因子CREB1，并证实IL-27促进IL-10表达的能力依赖于CREB1复合物成员p300的组蛋白乙酰转移酶活性。综上，本研究数据为IL-27调控免疫应答的作用机制提供了深入解析。我们提出，感染诱导产生的细胞因子信号可通过调控表观遗传变化，响应T细胞受体（TCR, T cell receptor）刺激并调节细胞因子分泌水平，从而在感染部位调控免疫活性。实验整体设计：共20个样本；包括未致敏B6小鼠样本、初次免疫样本（第10天）、记忆性样本（第35天）以及二次免疫样本（第6天）