许多实验系统已被利用来理解调节T细胞的发育和功能中的免疫应答的机制。这里使用逆转录病毒转导的基因的方法的描述,这是经济,时间效率,最重要的是,高度信息识别调控通路。
Helper T cell development and function must be tightly regulated to induce an appropriate immune response that eliminates specific pathogens yet prevents autoimmunity. Many approaches involving different model organisms have been utilized to understand the mechanisms controlling helper T cell development and function. However, studies using mouse models have proven to be highly informative due to the availability of genetic, cellular, and biochemical systems. One genetic approach in mice used by many labs involves retroviral transduction of primary helper T cells. This is a powerful approach due to its relative ease, making it accessible to almost any laboratory with basic skills in molecular biology and immunology. Therefore, multiple genes in wild type or mutant forms can readily be tested for function in helper T cells to understand their importance and mechanisms of action. We have optimized this approach and describe here the protocols for production of high titer retroviruses, isolation of primary murine helper T cells, and their transduction by retroviruses and differentiation toward the different helper subsets. Finally, the use of this approach is described in uncovering mechanisms utilized by microRNAs (miRNAs) to regulate pathways controlling helper T cell development and function.
The immune response must be highly regulated to eliminate infections but prevent attacks on self-tissue that lead to autoimmunity. Helper T cells play an essential role in regulating the immune response, and a great deal of effort has been undertaken to understand their development and function (illustrated in several recent reviews 1-3). However, many questions remain, and many approaches have been utilized to study the mechanisms controlling helper T cell development and function. These have ranged from the use of in vitro cell culture systems to whole animals. Cell culture systems, especially those using cell lines, offer the benefit of ease of use and the ability to generate large amount of material to do sophisticated biochemical analyses. However, they suffer from their limited ability to reproduce the actual conditions occurring in an immune response. In contrast, whole animal experiments offer the benefit of relevance, but they can suffer from difficulties in manipulation and the ability to perform precise controls in addition to their large costs and ethical implications. Nevertheless, the vast majority of helper T cells studies today still require the use of whole animal experiments involving primary T cells because of the inability of cell lines to duplicate the exact steps occurring in the whole animal. Therefore, it is essential to utilize cost effective approaches that are highly informative.
Genetics is one powerful tool to study helper T cell development and function, yet traditional methods involving gene knockouts or transgenes are time consuming and expensive so they are often out of reach of small labs. However, retroviral transduction offers a powerful, rapid and, cost effective genetic approach to study the mechanisms of specific gene products. Therefore, it is commonly used in papers studying helper T cell development and function.
We have optimized a procedure for retroviral transduction of helper T cells. It utilizes the pMIG (Murine stem cell virus-Internal ribosomal entry site-Green fluorescent protein) retroviral expression vector, in which the gene of interest can be cloned and thereby expressed from the retrovirus long terminal repeat (LTR) 4. In addition, downstream of the inserted gene of interest is an internal ribosome entry sequence (IRES) followed by the green fluorescent protein (GFP) gene so transduced cells can easily be followed by their expression of GFP. The vector was originally derived from the Murine Stem Cell Virus (MSCV) vectors, which contain mutations in repressor binding sites in the LTRs making them resistant to silencing and thus, giving high expression in many cell types including helper T cells 5,6. Production of high titer retrovirus requires a simple transient transfection protocol of human embryonic kidney (HEK) 293T cells with the MIG vector and a helper virus vector that expresses the retroviral GAG, Pol, and Env genes. For this the pCL-Eco helper virus vector 7 works well in producing high titer replication incompetent retroviruses.
Here these protocols for retroviral production and transduction of primary murine T cells are described in addition to some of our results using this approach to study miRNA regulation of gene expression controlling helper T cell differentiation. miRNAs are small RNAs of approximately 22 nucleotides in length that post-transcriptionally regulate gene expression by targeting homologous sequences in protein encoding messenger RNAs and suppressing translation and inducing message instability 8,9. miRNAs play critical roles in developmental gene regulation. They are essential in the earliest stages of development, as embryos that cannot produce miRNAs die at a very early stage 10. In addition miRNAs are important later on in the development of many tissues. They are thought to function by fine-tuning the expression of genes required for developmental programs 1. In helper T cells miRNAs play multiple roles and are required for regulatory T cell (Treg) development 11-14. We used retroviral transduction as a means to dissect the mechanisms of miRNA regulation of Treg differentiation 15. Through such studies important individual miRNAs were determined by retroviral-mediated overexpression. Subsequently, relevant genes regulated by these miRNAs were identified in order to understand the molecular pathways regulated by miRNAs in helper T cell differentiation.
基因的逆转录病毒介导的过表达是分析在辅助性T细胞功能的有力方式,因为它们的发育和功能通常是由关键调节的表达水平来确定。然而,结果的谨慎的解释是必要的,因为表达水平显著高于内源基因的引入可许多文物。因此,这种技术应该与其他组合以验证的函数的相关性。例如,表达应使用的siRNA或基因敲除(如果可用)降低表达的补充。随着miRNA的,我们通过使用过表达人工miRNA目标是充当竞争性抑制剂的miRNA的15个站点的病毒结合,与阻断过度的实验。逆转录病毒转导的细胞,也可在涉及RNA和蛋白质分析生物化学分析使用。然而,这些实验的一个主要限制是转导资源的效率ulting在转导和未转导的细胞的混合群。因此,这些试验将最有可能需要将GFP +群体的排序。最后, 在体外分化测定法应在体内实验相结合,这是可以实现的一种方式是由导的T细胞过继转移入小鼠和以下它们的分化和它们对免疫反应的影响。
一的该系统的主要限制是,可以打包成逆转录病毒衣壳的RNA基因组的大小。根据我们的经验,为MIG逆转录病毒系统的最大插入尺寸提供了良好的病毒生产3-3.5 KB。因此,更大的基因不能与本系统进行分析,因为它们给差病毒滴度。然而,所以该系统是用于各种基因研究的有用大多数基因比该尺寸更小。
与逆转录病毒转导,这些protoco内的几个备选方案LS已经使用。许多研究者已经利用稳定表达逆转录病毒的基因(例如参照图16)的包装细胞系。然而,我们已获得使用标准的HEK 293T细胞与PCL-生态辅助病毒载体的共转染的最高滴度。幼稚辅助性T细胞的分离,也可以通过细胞分选,而不是磁珠与细胞分离柱协议来实现,但这需要访问一个细胞分选仪,和用于排序时间的费用通常比珠试剂高。最后,还有上用于区分的辅助T细胞分化成不同子集的激活条件的变化。例如,细胞太久的TCR刺激暴露在调节性T细胞诱导条件才能抑制其诱导16。因为逆转录病毒表达需要通过细胞的刺激诱导的细胞分裂这可能是一个问题。然而,我们发现使用此协议与O / N ACTIV高效的调节性T细胞的诱导通货膨胀之前的逆转录病毒转导。
内的这些协议,成功的应用需要几个因素。高滴度逆转录病毒制剂需要的HEK 293T细胞所以高质量DNA并精确地制备2×HBS的有效转染是重要的。此外,HEK 293T细胞的细胞密度需要是在转染的点大约50%,因为转染DNA的良好表达需要将细胞活跃生长的,这将被抑制,如果所述细胞是过于稀疏或密集。在转染过程中最佳密度细胞应在在病毒收集步骤某一点达到汇合,但他们将继续一路过关斩将到最后一集生产高滴度的病毒股票。辅助性T细胞的有效分化需要良好的小区质量,以便确保分离的细胞是在图1所示的纯度。同样地,小区的质量取决于小鼠FROM他们被隔离。对于这些研究,我们使用6-8周龄C57BL / 6小鼠。老年小鼠可具有少幼稚细胞,以及其他菌株可以在其分化不同。例如,如上所述,C57BL / 6的T细胞可能难以诱导Th2应答BALB / c小鼠更容易比C57BL / 6小鼠17这样的Th2应答。此外,任何的分化条件可从实验室稍有变化,以实验室,和基因表达的效果可能仅成为在亚最佳条件表观所以在各偏振条件的细胞因子的浓度可能需要被滴定。最后,对细胞增殖的过表达的基因的作用或偏振条件可以影响转导效率的目的基因的,以便测量效果可能需要优化偏振试剂的定时和浓度。优化所有这些因素应导致该系统信息的结果。
The authors have nothing to disclose.
This work was supported by a Biotechnology and Biological Sciences Research Council (BBSRC) grant (BB/H018573/1) and a BD Biosciences grant.
RPMI | Sigma | R8758 | |
DMEM | Sigma | D5671 | |
Penicillin Streptomycin solution | Sigma | P4333 | |
L-Glutamine | Sigma | G7513 | |
β-mercaptoethanol | Sigma | M3148 | |
DPBS | Sigma | D8537 | |
MIG vector | Addgene | Plasmid 9094 | |
pCL-Eco vector | Addgene | Plasmid 12371 | |
Cell strainer | BD Falcon | 352350 | |
Magnetic beads mouse CD4 cell kit | Invitrogen (Dynabeads) | 11415D | |
Streptavidin Beads | Miltenyi Biotech | 130-048-102 | |
MS cell separation columns | Miltenyi Biotech | 130-042-201 | |
LS cell separation columns | Miltenyi Biotech | 130-042-401 | |
CD25 Biotenylated MAb | BD Biosciences | 85059 | clone 7D4 |
CD62L Biotenylated MAb | BD Biosciences | 553149 | clone MEL-14 |
Polybrene (Hexadimethrine Bromide) | Sigma | 107689 | |
Anti-CD3 | eBiosciences | 16-0031-85 | clone 145-2C11 |
Anti-CD28 | eBiosciences | 16-0281-85 | clone 37.51 |
Anti-IL-4 | BD Biosciences | 559062 | clone 11B11 |
Anti-IFN-gamma | BD Biosciences | 559065 | clone XMG1.2 |
Anti-IL-2 | BD Biosciences | 554425 | cloneJES6-5H4 |
Recombinant IL-12 p70 | eBiosciences | 14-8121 | |
Recombinant IL-4 | BD Biosciences | 550067 | |
Recombinant TGF-beta | eBiosciences | 14-8342-62 | |
Recombinant IL-6 | eBiosciences | 14-8061 | |
Recombinant IL-2 | eBiosciences | 14-8021 | |
PMA | Sigma | P8139 | |
Ionomycin | Sigma | I0634 | |
Brefeldin A | eBiosciences | 00-4506 | |
Paraformaldehyde | Sigma | 16005 | Paraformaldehyde is toxic so use appropriate caution when handling |
Foxp3 staining buffer set | eBiosciences | 00-5523 | |
Anti-CD4 FITC | eBiosciences | 11-0041 | clone GK1.5 |
Anti-CD8a perCP-cy5.5 | eBiosciences | 45-0081-80 | clone 53-6.7 |
Anti-MHCII PE | eBiosciences | 12-0920 | clone HIS19 |
Anti-CD25 PE | eBiosciences | 12-0251-82 | clone PC61.5 |
Anti-CD62L PE | eBiosciences | 12-0621-82 | clone MEL-14 |
Anti-CD44 APC | eBiosciences | 17-0441 | clone IM7 |
Anti-IFN-gamma FITC | eBiosciences | 11-7311-81 | clone XMG1.2 |
Anti-IL-4 PE | BD Biosciences | 554435 | clone 11B11 |
Anti-IL-9 PE or APC | eBiosciences/Biolegend | 50-8091-82/514104 | clone RM9A4 |
Anti-IL-17a PE | BD Biosciences | 559502 | clone TC11-18H10 |
Anti-Foxp3 APC or PE | eBiosciences | 17-5773-82/12-5773-80 | clone FJK-16s |
NaCl | Sigma | S7653 | |
KCl | Sigma | P9333 | |
Na2HPO4-2H2O | Sigma | 71643 | |
Dextrose/Glucose | Sigma | G7021 | |
HEPES, free acid | Sigma | H3375 | |
NH4Cl | Sigma | A9434 | |
Disodium EDTA | Sigma | D2900000 | |
KHCO3 | Sigma | 237205 | |
CaCl2 | Sigma | C5670 |