Data_Sheet_8_Biogenesis of HLA Ligand Presentation in Immune Cells Upon Activation Reveals Changes in Peptide Length Preference.PDF

Induction of an effective tumor immunity is a complex process that includes the appropriate presentation of the tumor antigens, activation of specific T cells, and the elimination of malignant cells. Potent and efficient T cell activation is dependent on multiple factors, such as timely expression of co-stimulatory molecules, the differentiation state of professional antigen presenting cells (e.g., dendritic cells; DCs), the functionality of the antigen processing and presentation machinery (APPM), and the repertoire of HLA class I and II-bound peptides (termed immunopeptidome) presented to T cells. So far, how molecular perturbations underlying DCs maturation and differentiation affect the in vivo cross-presented HLA class I and II immunopeptidomes is largely unknown. Yet, this knowledge is crucial for further development of DC-based immunotherapy approaches. We applied a state-of-the-art sensitive MS-based immunopeptidomics approach to characterize the naturally presented HLA-I and -II immunopeptidomes eluted from autologous immune cells having distinct functional and biological states including CD14+ monocytes, immature DC (ImmDC) and mature DC (MaDC) monocyte-derived DCs and naive or activated T and B cells. We revealed a presentation of significantly longer HLA peptides upon activation that is HLA allotype specific. This was apparent in the self-peptidome upon cell activation and in the context of presentation of exogenously loaded antigens, suggesting that peptide length is an important feature with potential implications on the rational design of anti-cancer vaccines.

诱导有效抗肿瘤免疫是一个复杂的过程，涵盖肿瘤抗原的精准呈递、特异性T细胞活化以及恶性细胞清除等多个环节。强效且高效的T细胞活化依赖于多重因素，包括共刺激分子的适时表达、专职抗原呈递细胞（如树突状细胞（dendritic cells）；DCs）的分化状态、抗原加工呈递系统（antigen processing and presentation machinery, APPM）的功能活性，以及呈递给T细胞的HLA I类与II类结合肽库（称为免疫肽组（immunopeptidome））。迄今为止，DCs成熟与分化背后的分子扰动如何调控体内交叉呈递的HLA I类与II类免疫肽组，这一问题尚不明晰。然而，该领域的认知对于基于DC的免疫治疗策略的进一步开发至关重要。本研究采用当前最先进的高灵敏度基于质谱（MS）的免疫肽组学方法，对从不同功能与生物学状态的自体免疫细胞中洗脱得到的天然呈递HLA I类与II类免疫肽组进行表征，这些自体免疫细胞包括CD14+单核细胞、单核细胞衍生的未成熟树突状细胞（immature DC, ImmDC）与成熟树突状细胞（mature DC, MaDC），以及初始或活化的T、B细胞。本研究发现，细胞活化后呈递的HLA肽段长度显著更长，且该现象具有HLA同种异型特异性。该现象在细胞活化后的自身肽组中，以及外源负载抗原的呈递场景中均显著存在，这表明肽段长度是一项重要特征，对抗癌疫苗的合理设计具有潜在指导意义。