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

Abstract

Idiosyncratic DILI is a challenging condition, believed to involve the immune system. This hypothesis is supported by various identified HLA risk alleles. To evaluate a potential role of the immune system in DILI through leukocyte immunophenotyping. 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. 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. 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