Background/Aims: The occurrence and development of hepatitis B virus-associated acute-onchronic liver failure (HBV-ACLF) is closely related to the immune pathway. We explored the heterogeneity of peripheral blood T cell subsets and the characteristics of exhausted T lymphocytes, in an attempt to identify potential therapeutic target molecules for immune dysfunction in ACLF patients. Methods: A total of 83,577 T cells from HBV-ACLF patients and healthy controls were screened for heterogeneity by single-cell RNA sequencing. In addition, exhausted T-lymphocyte subsets were screened to analyze their gene expression profiles, and their developmental trajectories were investigated. Subsequently, the expression of exhausted T cells and their capacity in secreting cytokines (interleukin 2, interferon γ, and tumor necrosis factor α) were validated by flow cytometry. Results: A total of eight stable clusters were identified, among which CD4 + TIGIT + subset and CD8 + LAG-3 + subset, with high expression of exhaust genes, were significantly higher in the HBV-ACLF patients than in normal controls. As shown by pseudotime analysis, T cells experienced a transition from naïve T cells to effector T cells and then exhausted T cells. Flow cytometry confirmed that the CD4 + TIGIT + subset and CD8 + LAG-3 + subset in the peripheral blood of the ACLF patients were significantly higher than those in the healthy controls. Moreover, in vitro cultured CD8 + LAG-3 + T cells were significantly fewer capable of secreting cytokines than CD8 + LAG-3- subset. Conclusions Peripheral blood T cells are heterogeneous in HBV-ACLF. The exhausted T cells markedly increase during the pathogenesis of ACLF, suggesting that T-cell exhaustion is involved in the immune dysfunction of HBV-ACLF patients.

Acute-on-chronic liver failure (ACLF) is a syndrome characterized by multiple organ failure and high short-term mortality rate, and it has always been a research hotspot in the field of severe liver diseases. Therefore, early and accurate risk stratification and timely intervention are of great significance to improve prognosis. This article summarizes the serum biomarkers identified in recent years for evaluating the prognosis of patients with ACLF, and it is pointed out that new serum biomarkers have an important guiding significance in the prognostic evaluation of ACLF patients.