Spatial heterogeneity and peptide availability determine CTL killing efficiency in vivo.
Spatial heterogeneity and peptide availability determine CTL killing efficiency in vivo.
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DOI：
10.1371/journal.pcbi.1003805
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发表时间：
2014-09
影响因子：
4.3
通讯作者：
Yates A
中科院分区：
文献类型：
--
作者：
Hogan T;Kadolsky U;Tung S;Seddon B;Yates A
细胞毒性T淋巴细胞(CTL)检测感染细胞的速度是脊椎动物对细胞内病原体免疫反应模型的关键因素。在体内细胞毒性试验中，CTL在免疫小鼠的脾中杀死多肽脉冲的脾细胞，从而获得了估计。然而，脾是一个异质的环境，脾细胞由多种类型的细胞组成。是不是某些类型的细胞天生比其他类型的细胞更容易裂解？在定量方面，靶标和效应物的空间分布以及靶细胞表面多肽-MHC的水平会产生什么影响？为了解决这些问题，我们回顾了脾细胞杀伤试验，使用针对流感病毒表位的CTL。我们发现，在细胞群体水平上，T细胞靶标被杀死的速度比B细胞更快。利用建模、定量成像和体外杀伤试验，我们得出结论，这种体内差异可能反映了脾内靶标的不同迁移模式和CTL的异质性分布，两个群体对裂解的内在易感性没有明显差异。对体外检测和杀伤多肽脉冲靶标所涉及的各个阶段的模拟表明，多肽剂量影响CTL与靶标形成偶联的能力，但对偶联导致裂解的概率没有可检测到的影响，并且T细胞靶标的裂解时间比B细胞长。我们还推断，用低剂量多肽冲击的细胞在体内的不完全杀伤可能是由于多肽摄取的异质性和多肽-MHC复合体的解离而不是内化的共同作用。我们的分析表明，免疫反应模型中的群体平均参数如何被剖析以解释空间和细胞的异质性。单个细胞毒性T淋巴细胞(CTL)检测感染细胞并在接触时将其杀死的比率的测量，对于构建脊椎动物对细胞内病原体的免疫反应的预测模型非常重要。以前使用建模和实验相结合的方法估计了监测率，假设CTL和靶细胞很好地混合在一起，所有类型的细胞都以同样的效率被杀死。在这项研究中，我们采取了理论和实验相结合的迭代方法，超越了这样的模型，详细讨论了细胞异质性的影响，发生杀戮的组织的空间组织，以及多肽在靶细胞表面表达水平的影响。我们证明，确定效应细胞和靶细胞的共定位程度，以及靶细胞上的多肽表达水平，对于提高CTL杀伤率的估计是最重要的。此外，虽然CTL与T和B细胞靶标结合后的杀伤概率相似，但T细胞比B细胞需要更长的时间才能杀伤，当CTL数量有限时，这一效果可能会很重要。
The rate at which a cytotoxic T lymphocyte (CTL) can survey for infected cells is a key ingredient of models of vertebrate immune responses to intracellular pathogens. Estimates have been obtained using in vivo cytotoxicity assays in which peptide-pulsed splenocytes are killed by CTL in the spleens of immunised mice. However the spleen is a heterogeneous environment and splenocytes comprise multiple cell types. Are some cell types intrinsically more susceptible to lysis than others? Quantitatively, what impacts are made by the spatial distribution of targets and effectors, and the level of peptide-MHC on the target cell surface? To address these questions we revisited the splenocyte killing assay, using CTL specific for an epitope of influenza virus. We found that at the cell population level T cell targets were killed more rapidly than B cells. Using modeling, quantitative imaging and in vitro killing assays we conclude that this difference in vivo likely reflects different migratory patterns of targets within the spleen and a heterogeneous distribution of CTL, with no detectable difference in the intrinsic susceptibilities of the two populations to lysis. Modeling of the stages involved in the detection and killing of peptide-pulsed targets in vitro revealed that peptide dose influenced the ability of CTL to form conjugates with targets but had no detectable effect on the probability that conjugation resulted in lysis, and that T cell targets took longer to lyse than B cells. We also infer that incomplete killing in vivo of cells pulsed with low doses of peptide may be due to a combination of heterogeneity in peptide uptake and the dissociation, but not internalisation, of peptide-MHC complexes. Our analyses demonstrate how population-averaged parameters in models of immune responses can be dissected to account for both spatial and cellular heterogeneity. Measurements of the rates at which a single cytotoxic T lymphocyte (CTL) can survey for infected cells, and kill them upon encounter, are important for constructing predictive models of vertebrate immune responses to intracellular pathogens. The surveillance rate has been estimated previously using combinations of modeling and experiment, making the assumption that CTL and target cells are well-mixed and that all cell types are killed with equal efficiency. In this study we take an iterative approach with theory and experiment to go beyond such models and detail the effects of cellular heterogeneity, the spatial organisation of the tissue within which killing is taking place, and the influence of the level of expression of peptides on the target cell surface. We demonstrate that determining the degree of co-localisation of effector and target cells, and the level of peptide expression on targets, are most important for improving estimates of CTL killing rates. Further, while the probabilities of killing upon conjugation of CTL with T and B cell targets are similar, T cells take substantially longer to kill than B cells, an effect that may be important when CTL numbers are limiting.
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影响因子：
3.7
作者：
Ganusov VV;Lukacher AE;Byers AM
通讯作者：
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影响因子：
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作者：
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通讯作者：
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DOI：
10.1098/rspb.2011.0453
发表时间：
2011-11-22
影响因子：
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通讯作者：
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DOI：
10.1084/jem.20091279
发表时间：
2010-01-18
期刊：
The Journal of experimental medicine
影响因子：
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作者：
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通讯作者：
Silverstein SC
影响因子：
30.5
作者：
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通讯作者：
von Andrian, Ulrich H.