组织内发生的免疫和炎症过程通常无法通过血细胞计数、常规循环生物标志物或成像检测到，这代表了未满足的生物医学需求。在这里，我们概述最近的进展，表明液体活检可以广泛地了解人类免疫系统动态。细胞自由DNA (cfDNA) 的核小体大小片段从死亡细胞释放到血液中，包含丰富的表观遗传信息，如甲基化、断裂和组蛋白标记模式。这些信息可以推断出 cfDNA 细胞的起源，以及细胞死亡前的基因表达模式。我们提出，分析免疫细胞来源的 cfDNA 的表观遗传特征可以揭示健康人群中免疫细胞周转动态，并告知癌症、局部炎症、感染性或自身免疫性疾病，以及对疫苗的反应的研究和诊断。版权所有© 2023 Elsevier Ltd。保留所有权利。

Immune and inflammatory processes occurring within tissues are often undetectable by blood cell counts, standard circulating biomarkers, or imaging, representing an unmet biomedical need. Here, we outline recent advances indicating that liquid biopsies can broadly inform human immune system dynamics. Nucleosome-size fragments of cell-free DNA (cfDNA) released from dying cells into blood contain rich epigenetic information such as methylation, fragmentation, and histone mark patterns. This information allows to infer the cfDNA cell of origin, as well as pre-cell death gene expression patterns. We propose that the analysis of epigenetic features of immune cell-derived cfDNA can shed light on immune cell turnover dynamics in healthy people, and inform the study and diagnosis of cancer, local inflammation, infectious or autoimmune diseases, as well as responses to vaccination.Copyright © 2023 Elsevier Ltd. All rights reserved.