O-2 ROLE OF IMMUNE CHECKPOINTS AND ACTIVATED HELPER AND CYTOTOXIC T-CELLS IN DRUG-INDUCED LIVER INJURY (DILI)

Abstract

Introduction: Idiosyncratic DILI is a challenging condition, believed to involve the immune system. This hypothesis is supported by various identified HLA risk alleles. Objectives: To evaluate a potential role of the immune system in DILI through leukocyte immunophenotyping. Methods: Blood samples were collected from adjudicated DILI (n=12) and viral hepatitis (VH, 13) at day 1 (recognition), 7 and >30. A single blood sample was extracted from healthy liver controls (HLC, 54). Leukocyte populations and immune checkpoint expressions were determined based on cell surface receptors, except for CTLA-4 that was determined intracellularly, using multiparametric flow cytometry. Results: No differences were detected in leukocytes, lymphocytes or neutrophils counts at day 1. However, DILI (0.57 × 10E09/L, p=0.037) and HV (1.41 × 10E09/L, p<0.0001) had increased monocyte levels than HLC (0.35 × 10E09/L). At day 1 DILI presented higher levels of activated helper T-cells (CD4+/DR+) and activated cytotoxic T-cells (CD8+/DR+) than HLC (14%vs6.3%, p<0.0001; 31%vs15%, p=0.0003, respectively). The same trend was detected for VH. A strong correlation between activated CD4+ and CD8+ was found in DILI (r=0.85, p<0.001), but less in VH (r=0.58, p=0.0015). Regarding helper T-cell subpopulations, DILI had higher level of Th1 (52vs42%, p=0.0358), while VH had lower level of Th9 than HLC (13%vs18%, p=0.0112). Regarding immune checkpoint expressions on CD4+, DILI presented higher intracellular CTLA-4 level than HLC (28%vs18%, p=0.0192). Higher expression of checkpoint ligand PD-1L on monocytes was also found in DILI (5.3%vs3.4%, p=0.0452) and VH (9.1%vs3.4%, p<0.0001). The level of all leukocyte populations and checkpoint expressions in DILI and VH approached HLC levels in the later samples, except for CD28 and CD86 that are constitutively expressed. Conclusion: Our findings suggest that an adaptive immune response is involved in DILI in which activated CD4+ and CD8+ play important roles. Increased expression of negative immune checkpoints and ligands reflects restoration of immune homeostasis. Funding:PI16/01748, PI19/00883, CIBERehd-ISCIII