Unveiling Dynamic Changes and Regulatory Mechanisms of T Cell Subsets in Sepsis Pathogenesis.

Purpose: The pathogenesis of T cell subsets in sepsis during the body's resistance to infection is currently unknown. We aimed to investigate the dynamics and molecular mechanisms of T cells during the development of sepsis.

Patients and methods: Perform single-cell data analysis on peripheral blood mononuclear cells (PBMCs) specimen samples from seven healthy controls, five early-stage sepsis patients, and four late sepsis patients, and the atlas were mapped and analyzed using reference mapping to identify the T cell subpopulations specific to early sepsis. Expression network upstream to investigate the changes of regulatory transcription factors and pathways by pySCENIC.

Results: Twenty-two CD4⁺ T-cell subpopulations and 10 CD8⁺ T-cell subpopulations were identified by mapping analysis. At the early stage of sepsis, we observed altered ratios of multiple immune cells in PBMCs. Three cell types CD4 Tn cells, CD8 (GZMK⁺ early Tem), and CD8 (ZNF683⁺CXCR6^- Tm) showed an upward trend (p < 0.05) in the early stages of sepsis compared to normal and returned to normal levels after two weeks. In addition, we found the presence of four sepsis-specific transcription factors (MXI1, CHD1, ARID5A, KLF9) in these three types of cells, which were validated in two external datasets. The differentially expressed genes in CD4 Tn cells, CD8 (GZMK⁺ early Tem), and CD8 (ZNF683⁺CXCR6^- Tm) cells between the healthy group and the early-stage sepsis group are commonly enriched in the allograft rejection pathway. In addition, it was found that CD8 cells exhibit a trend towards differentiation into CD8 Temra cells in sepsis.

Conclusion: We successfully depicted the dynamic changes of T cell subsets during sepsis onset and progression, which provides important clues for an in-depth understanding of T cells' function and regulatory mechanisms during sepsis pathogenesis.