Neonatal CD4+ T cells have a characteristic transcriptome and epigenome and respond to TCR stimulation with proliferation and yet a limited immune response

The adaptive immune response is coordinated by CD4+ T cells, which determine the type and strength of the immune response and the effector cells involved. It has been reported that CD4+ T cells are less responsive in neonates, leading to low activation of the cellular response and poor antibody production by B cells. This low response is essential for the tolerant window that favors birth transition from the sterile environment in the womb to the outside world but leaves neonates vulnerable to infection, which is still an important health issue. Neonates have a high morbidity and mortality rate due to infections, and the molecular reasons are still understudied. We asked whether the neonatal naive CD4+ T cells have a genomic program that predisposes them to a low response. Therefore, we evaluated the transcriptome and epigenome of human neonatal and adult naive CD4+ T cells. Our results point to a gene expression profile forming a distinct regulatory network in neonatal cells, which favors proliferation and a low T-cell response. Such expression profile is supported by a characteristic epigenetic landscape of neonatal CD4+ T cells, which correlates with the characteristic transcriptome of the neonatal cells. These results were confirmed by experiments showing a low response to activation signals, higher proliferation, and lower expression of cytokines of neonatal CD4+ T cells as compared to adult cells. Understanding this network could lead to novel vaccine formulations and better deal with life-threatening diseases during this highly vulnerable period of our lives. CD4+T cells were cultured in RPMI 1640 medium supplemented with 2 mM glutamine, commercial antibiotics (50 U/mL penicillin,50lg/mL streptomycin) and 5% fetal coalf serum. Cells were activated with 1µg/mL anti-CD3 (OKT3; TONBO Bio-sciences) and 1µg/mL anti-CD28 (CD28.2;TONBO Biosciences) , cross-linked with 1ug/mL goat anti-mouse (Polyclonal,Bioss) and incubated for 6 h under 5% CO2 at 37°C

适应性免疫应答由CD4+ T细胞协调，后者决定免疫应答的类型、强度以及所涉及的效应细胞。已有研究表明，新生儿体内的CD4+ T细胞应答较弱，导致细胞应答激活水平低下，且B细胞产生抗体的能力不佳。这种低应答状态对于促成胎儿从子宫无菌环境向外界环境过渡的耐受窗口至关重要，但同时也使新生儿易受感染——这至今仍是一项重要的健康问题。新生儿因感染导致的发病率和死亡率居高不下，其分子机制仍有待深入研究。我们旨在探究新生儿初始CD4+ T细胞是否存在使其倾向于产生低应答的基因组程序。为此，我们对人类新生儿与成人初始CD4+ T细胞的转录组（transcriptome）与表观基因组（epigenome）进行了分析。研究结果显示，新生儿细胞中存在一套独特的基因表达调控网络，该网络倾向于促进细胞增殖并维持T细胞低应答状态。这类表达特征得到了新生儿CD4+ T细胞特有的表观遗传图谱的支持，其与新生儿细胞的特征性转录组特征高度相关。上述结果通过实验得到了验证：与成人细胞相比，新生儿CD4+ T细胞对激活信号的应答较弱、增殖能力更强，且细胞因子表达水平更低。阐明这一调控网络或可助力开发新型疫苗制剂，帮助我们在人生这一高度易感的阶段更好地应对危及生命的疾病。CD4+ T细胞培养于添加了2 mM谷氨酰胺、商品化抗生素（50 U/mL青霉素、50 μg/mL链霉素）以及5%胎牛血清的RPMI 1640培养基中。细胞采用1 μg/mL抗CD3（OKT3；TONBO Bio-sciences）与1 μg/mL抗CD28（CD28.2；TONBO Biosciences）进行激活，并以1 μg/mL山羊抗小鼠抗体（多克隆，Bioss）进行交联，随后于37℃、5% CO₂条件下孵育6小时。