Presentation of peptides by class I MHC proteins underlies T cell immune responses to pathogens and cancer. The association between peptide binding affinity and immunogenicity has led to the engineering of modified peptides with improved MHC binding, with the hope that these peptides would be useful for eliciting cross-reactive immune responses directed toward their weak binding, unmodified counterparts. Increasing evidence, however, indicates that T cell receptors (TCRs) can perceive such anchor-modified peptides differently than wild-type (WT) peptides, although the scope of discrimination is unclear. We show here that even modifications at primary anchors that have no discernible structural impact can lead to substantially stronger or weaker T cell recognition depending on the TCR. Surprisingly, the effect of peptide anchor modification can be sensed by a TCR at regions distant from the site of modification, indicating a through-protein mechanism in which the anchor residue serves as an allosteric modulator for TCR binding. Our findings emphasize caution in the use and interpretation of results from anchor-modified peptides and have implications for how anchor modifications are accounted for in other circumstances, such as predicting the immunogenicity of tumor neoantigens. Our data also highlight an important need to better understand the highly tunable dynamic nature of class I MHC proteins and the impact this has on various forms of immune recognition.

I 类 MHC 蛋白呈递肽是 T 细胞对病原体和癌症的免疫反应的基础。肽结合亲和力和免疫原性之间的关联导致了具有改进的 MHC 结合的修饰肽的工程设计，希望这些肽可用于引发针对其弱结合、未修饰对应物的交叉反应性免疫应答。然而，越来越多的证据表明，T 细胞受体 (TCR) 能够以不同于野生型 (WT) 肽的方式感知此类锚定修饰肽，尽管区分范围尚不清楚。我们在这里表明，即使对主要锚点的修饰没有明显的结构影响，也可能导致 T 细胞识别明显更强或更弱，具体取决于 TCR。令人惊讶的是，肽锚定修饰的效果可以被远离修饰位点的区域的TCR感知，这表明锚定残基作为TCR结合的变构调节剂的贯穿蛋白质机制。我们的研究结果强调了在使用和解释锚定修饰肽结果时要谨慎，并对如何在其他情况下解释锚定修饰具有影响，例如预测肿瘤新抗原的免疫原性。我们的数据还强调了更好地了解 I 类 MHC 蛋白的高度可调动态性质及其对各种形式的免疫识别的影响的重要需求。