Department of Biochemistry, University of Illinois, Urbana, IL 61801.
Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, United Kingdom.
J Immunol. 2018 Feb 1;200(3):1088-1100. doi: 10.4049/jimmunol.1700236. Epub 2017 Dec 29.
Adoptive T cell therapies have achieved significant clinical responses, especially in hematopoietic cancers. Two types of receptor systems have been used to redirect the activity of T cells, normal heterodimeric TCRs or synthetic chimeric Ag receptors (CARs). TCRs recognize peptide-HLA complexes whereas CARs typically use an Ab-derived single-chain fragments variable that recognizes cancer-associated cell-surface Ags. Although both receptors mediate diverse effector functions, a quantitative comparison of the sensitivity and signaling capacity of TCRs and CARs has been limited due to their differences in affinities and ligands. In this study we describe their direct comparison by using TCRs that could be formatted either as conventional αβ heterodimers, or as single-chain fragments variable constructs linked to CD3ζ and CD28 signaling domains or to CD3ζ alone. Two high-affinity TCRs (K values of ∼50 and 250 nM) against MART1/HLA-A2 or WT1/HLA-A2 were used, allowing MART1 or WT1 peptide titrations to easily assess the impact of Ag density. Although CARs were expressed at higher surface levels than TCRs, they were 10-100-fold less sensitive, even in the absence of the CD8 coreceptor. Mathematical modeling demonstrated that lower CAR sensitivity could be attributed to less efficient signaling kinetics. Furthermore, reduced cytokine secretion observed at high Ag density for both TCRs and CARs suggested a role for negative regulators in both systems. Interestingly, at high Ag density, CARs also mediated greater maximal release of some cytokines, such as IL-2 and IL-6. These results have implications for the next-generation design of receptors used in adoptive T cell therapies.
过继性 T 细胞疗法已取得显著的临床疗效，尤其在血液系统恶性肿瘤中。目前已有两种受体系统被用于重定向 T 细胞的活性，即正常的异二聚体 TCR 或合成嵌合抗原受体（CAR）。TCR 识别肽-HLA 复合物，而 CAR 通常使用抗体衍生的单链可变片段来识别与癌症相关的细胞表面抗原。尽管这两种受体都介导了多样化的效应功能，但由于 TCR 和 CAR 在亲和力和配体方面的差异，对它们的敏感性和信号转导能力进行定量比较一直受到限制。在这项研究中，我们通过使用既可以形成常规的 αβ 异二聚体，也可以与 CD3ζ 和 CD28 信号结构域或单独的 CD3ζ 相连的单链可变片段构建体的 TCR，对它们进行了直接比较。我们使用了两种针对 MART1/HLA-A2 或 WT1/HLA-A2 的高亲和力 TCR（K 值分别约为 50 和 250 nM），允许进行 MART1 或 WT1 肽滴定，以轻松评估抗原密度的影响。尽管 CAR 的表面表达水平高于 TCR，但即使在没有 CD8 共受体的情况下，CAR 的敏感性也低 10-100 倍。数学模型表明，CAR 敏感性较低可能归因于信号转导动力学效率较低。此外，在高抗原密度下，两种 TCR 和 CAR 观察到细胞因子分泌减少，这表明在这两个系统中都存在负调控因子。有趣的是，在高抗原密度下，CAR 还介导了一些细胞因子（如 IL-2 和 IL-6）的更大的最大释放。这些结果对过继性 T 细胞疗法中受体的下一代设计具有重要意义。
