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Background and Aims: Acute liver failure is a multisystem disorder with a high mortality and frequent need for emergency liver transplantation. Following massive innate immune system activation, soluble markers of macrophage activation are released during liver damage and their association with disease severity and prognosis requires exploration. Methods: Patients ALF from the United States Acute Liver Failure Study Group (USALFSG, n = 224) and King's College Hospital (n = 40) together with healthy controls (HC, n = 50) were recruited. Serum from early (Days 1–3) and late (>Day 3) time points were analysed for MAMs by enzyme‐linked immunosorbent assay correlated to markers of illness severity and 21‐day spontaneous survival. Surface expression phenotyping was performed via Flow Cytometry on CD14+ monocytes. Results: All MAMs serum concentrations were significantly higher in ALF compared to controls (p <.0001). sCD206 concentration was higher in early and late stages of the disease in patients with bacteraemia (p =.002) and infection in general (p =.006). In MELD‐adjusted multivariate modelling, sCD206 and sCD163 were independently associated with mortality. CD14+ monocyte expression of CD206 (p <.001) was higher in patients with ALF compared with controls and correlated with SOFA score (p =.018). sCD206 was independently validated as a predictor of infection in an external cohort. Conclusions: sCD206 is increased in serum of ALF patients with infections and poor outcome and is upregulated on CD14+ monocytes. Later measurements of sCD163 and sCD206 during the evolution of ALF have potential as mechanistic predictors of mortality. sCD206 should be explored as a biomarker of sepsis and mortality in ALF. [ABSTRACT FROM AUTHOR]

Introduction Acute liver failure (ALF) is a rare clinical syndrome in which coagulopathy, jaundice, and hepatic encephalopathy arise in the context of acute hepatic injury without preexisting chronic liver disease [...], Patients with acute liver failure (ALF) have systemic innate immune suppression and increased susceptibility to infections. Programmed cell death 1 (PD-1) expression by macrophages has been associated with immune suppression during sepsis and cancer. We therefore examined the role of the programmed cell death 1/programmed death ligand 1 (PD-1/PD-L1) pathway in regulating Kupffer cell (KC) inflammatory and antimicrobial responses in acetaminophen-induced (APAP-induced) acute liver injury. Using intravital imaging and flow cytometry, we found impaired KC bacterial clearance and systemic bacterial dissemination in mice with liver injury. We detected increased PD-1 and PD-L1 expression in KCs and lymphocyte subsets, respectively, during injury resolution. Gene expression profiling of [PD-1.sup.+] KCs revealed an immune-suppressive profile and reduced pathogen responses. Compared with WT mice, [PD-1.sup.-]deficient mice and anti-[PD-1.sup.-]treated mice with liver injury showed improved KC bacterial clearance, a reduced tissue bacterial load, and protection from sepsis. Blood samples from patients with ALF revealed enhanced PD-1 and PD-L1 expression by monocytes and lymphocytes, respectively, and that soluble PD-L1 plasma levels could predict outcomes and sepsis. PD-1 in vitro blockade restored monocyte functionality. Our study describes a role for the PD-1/PD-L1 axis in suppressing KC and monocyte antimicrobial responses after liver injury and identifies anti-PD-1 immunotherapy as a strategy to reduce infection susceptibility in ALF.

Author(s): Christine Bernsmeier [sup.1], Charalambos G. Antoniades [sup.1] [sup.2], Julia Wendon [sup.1] Author Affiliations: (1) grid.13097.3c, 0000000123226764, Liver Intensive Therapy Unit, Institute of Liver Studies, King's College London, , Denmark [...]

Changes in monocytes and their subsets (CD14hi/CD16neg, CD14hi/CD16pos and CD14lo/CD16pos) have been described in several diseases. The combination of CD14, CD16 and HLA-DR has been suggested to discriminate monocytes from the CD16pos/HLA-DRneg NK-cells and neutrophils but no data exist whether this strategy can be used in situations when monocyte HLA-DR expression is pathologically reduced. Monocytes and their subsets were concurrently identified through negative (exclusion of CD66bpos neutrophils, CD56pos NKcells, CD19pos B-cells, and CD3pos T-cells) and positive gating (inclusion of monocytes by expression of CD14, CD16, and HLA-DR) strategies on 30 occasions [9 healthy controls (HC) and 21 patients with conditions associated with low monocyte HLA-DR expression]. Bland-Altman and Passing and Bablok regression statistics did not demonstrate any significant measurement bias between the two strategies of monocyte identification. Monocyte subset phenotype was then compared in 18 HC and 41 patients with acute liver failure (ALF). Compared with HC, in ALF, the percentage of CD14hi/CD16pos monocytes was higher (7% vs 4%) whilst the percentage of CD14lo/CD16pos was lower (1.9% vs. 7%) ( P ≤ 0.001); HLA-DR and CD86 MFIs on all monocyte subsets were lower, whilst CCR5, CD64, and CD11b MFIs were higher ( P < 0.05). The relative expression by monocyte subsets of HLA-DR, CCR2, CCR5, CX3CR1, and CD11a was similar in ALF patients and HCs. Repeat analysis of an identical antibody-fluorochrome 'backbone' targeting HLA-DR, CD14, and CD16 was assessed in 189 samples across 5 different experiments. There was excellent agreement in the results obtained using the positive gating strategy (interclass correlation coefficients > 0.8). Monocytes and their subsets can be reliably identified using an antibody-fluorochrome 'backbone' of HLA-DR, CD14, and CD16. CD16pos monocytes continue to constitutively express HLA-DR even in conditions where HLA-DR is pathologically reduced on CD14hi/CD16neg monocytes. Understanding the changes in monocyte pheontype in ALF and similar clinico-pathological diseases may allow the development of novel biomarkers or therapeutic strategies. © 2012 International Society for Advancement of Cytometry [ABSTRACT FROM AUTHOR]

Background: Checkpoint inhibitor-induced hepatitis (CPI-hepatitis) is an emerging problem with the widening use of CPIs in cancer immunotherapy. Here, we developed a mouse model to characterize the mechanism of CPI-hepatitis and to therapeutically target key pathways driving this pathology., Methods: C57BL/6 wild-type (WT) mice were dosed with toll-like receptor (TLR)9 agonist (TLR9-L) for hepatic priming combined with anti-cytotoxic T lymphocyte antigen-4 (CTLA-4) plus anti-programmed cell death 1 (PD-1) ("CPI") or phosphate buffered saline (PBS) control for up to 7 days. Flow cytometry, histology/immunofluorescence and messenger RNA sequencing were used to characterize liver myeloid/lymphoid subsets and inflammation. Hepatocyte damage was assessed by plasma alanine transaminase (ALT) and cytokeratin-18 (CK-18) measurements . In vivo investigations of CPI-hepatitis were carried out in Rag2 -/- and Ccr2 rfp/rfp transgenic mice, as well as following anti-CD4, anti-CD8 or cenicriviroc (CVC; CCR2/CCR5 antagonist) treatment., Results: Co-administration of combination CPIs with TLR9-L induced liver pathology closely resembling human disease, with increased infiltration and clustering of granzyme B + perforin + CD8 + T cells and CCR2 + monocytes, 7 days post treatment. This was accompanied by apoptotic hepatocytes surrounding these clusters and elevated ALT and CK-18 plasma levels. Liver RNA sequencing identified key signaling pathways (JAK-STAT, NF- Κ B) and cytokine/chemokine networks ( Ifnγ, Cxcl9, Ccl2/Ccr2 ) as drivers of CPI-hepatitis. Using this model, we show that CD8 + T cells mediate hepatocyte damage in experimental CPI-hepatitis. However, their liver recruitment, clustering, and cytotoxic activity is dependent on the presence of CCR2 + monocytes. The absence of hepatic monocyte recruitment in Ccr2 rfp/rfp mice and CCR2 inhibition by CVC treatment in WT mice was able to prevent the development and reverse established experimental CPI-hepatitis., Conclusion: This newly established mouse model provides a platform for in vivo mechanistic studies of CPI-hepatitis. Using this model, we demonstrate the central role of liver infiltrating CCR2 + monocyte interaction with tissue-destructive CD8 + T cells in the pathogenesis of CPI-hepatitis and highlight CCR2 inhibition as a novel therapeutic target., Competing Interests: Competing interests: No, there are no competing interests., (© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Changes in monocytes and their subsets (CD14(hi)/CD16(neg), CD14(hi)/CD16(pos) and CD14(lo)/CD16(pos)) have been described in several diseases. The combination of CD14, CD16 and HLA-DR has been suggested to discriminate monocytes from the CD16(pos) /HLA-DR(neg) NK-cells and neutrophils but no data exist whether this strategy can be used in situations when monocyte HLA-DR expression is pathologically reduced. Monocytes and their subsets were concurrently identified through negative (exclusion of CD66b(pos) neutrophils, CD56(pos) NKcells, CD19(pos) B-cells, and CD3(pos) T-cells) and positive gating (inclusion of monocytes by expression of CD14, CD16, and HLA-DR) strategies on 30 occasions [9 healthy controls (HC) and 21 patients with conditions associated with low monocyte HLA-DR expression]. Bland-Altman and Passing and Bablok regression statistics did not demonstrate any significant measurement bias between the two strategies of monocyte identification. Monocyte subset phenotype was then compared in 18 HC and 41 patients with acute liver failure (ALF). Compared with HC, in ALF, the percentage of CD14(hi)/CD16(pos) monocytes was higher (7% vs 4%) whilst the percentage of CD14(lo)/CD16(pos) was lower (1.9% vs. 7%) (P ≤ 0.001); HLA-DR and CD86 MFIs on all monocyte subsets were lower, whilst CCR5, CD64, and CD11b MFIs were higher (P < 0.05). The relative expression by monocyte subsets of HLA-DR, CCR2, CCR5, CX3CR1, and CD11a was similar in ALF patients and HCs. Repeat analysis of an identical antibody-fluorochrome "backbone" targeting HLA-DR, CD14, and CD16 was assessed in 189 samples across 5 different experiments. There was excellent agreement in the results obtained using the positive gating strategy (interclass correlation coefficients > 0.8). Monocytes and their subsets can be reliably identified using an antibody-fluorochrome "backbone" of HLA-DR, CD14, and CD16. CD16(pos) monocytes continue to constitutively express HLA-DR even in conditions where HLA-DR is pathologically reduced on CD14(hi)/CD16(neg) monocytes. Understanding the changes in monocyte pheontype in ALF and similar clinico-pathological diseases may allow the development of novel biomarkers or therapeutic strategies., (Copyright © 2012 International Society for Advancement of Cytometry.)