介白素27和肝臟組織駐留T細胞在肝臟微環境中調控免疫耐受性的研究

Abstract

肝臟發炎是許多肝臟疾病的共同特徵，不受控的肝炎可能進一步造成肝臟損傷。例如乙型肝炎病毒感染，可能透過肝炎導致肝硬化和肝癌等。然而，肝臟過去被認為是免疫耐受器官，目前肝炎及肝臟免疫耐受機制仍不清楚。而調控免疫反應的細胞激素中，介白素27在過去研究中被認為同時具有促炎性及抑炎性的功能，其在肝臟微環境中扮演的角色仍需進一步研究探討。此外，組織駐留型記憶T細胞在近年被許多研究發現存在不同器官中，提供了對後續感染的增強保護。肝臟中也存在表達特定表徵的駐留型T細胞。 因此，本研究旨在探討介白素27及表達無唾液酸神經節苷脂的肝臟駐留型CD8 T細胞在肝臟免疫微環境中扮演的角色。研究結果顯示，乙型肝炎病毒誘導肝內介白素27產生，肝臟內介白素27濃度與病毒清除有統計顯著相關，並造成CD8 T細胞表達細胞耗竭表徵及減少干擾素-γ產生，使肝臟維持免疫耐受狀態。且清除巨噬細胞譜系細胞來源介白素27後，可以觀察到相同的結果。顯示乙型病毒轉染後巨噬細胞譜系細胞產生的介白素27，能使肝臟維持免疫耐受狀態。而單細胞定序分析結果顯示，肝內ASGM1陽性CD8 T細胞可以分為不同類群，其中具有與組織駐留型記憶T細胞相似基因表現的細胞群高表達干擾素-γ。透過過繼細胞實驗顯示，體外活化後的肝內ASGM1陽性CD8 T細胞具有促進肝炎發生的能力。肝內ASGM1陽性CD8 T細胞在肝臟免疫微環境中扮演促炎角色。 本研究為肝臟免疫微環境提供了新見解，透過乙型肝炎病毒轉染小鼠模型顯示介白素27在肝臟中具有維持免疫耐受的功能，顯示介白素27具有做為乙型肝炎治療標靶的潛力。過繼轉移實驗顯示ASGM1陽性CD8 T細胞扮演肝內免疫微環境中促炎性的角色，該細胞群則具有活化肝臟免疫反應的潛力。

Liver inflammation is a common feature of many liver diseases, and uncontrolled hepatitis can further cause liver damage. For example, hepatitis B virus (HBV) infection may lead to cirrhosis and liver cancer through inflammation. However, the liver has traditionally been considered an immune-tolerant organ, and the mechanisms of hepatitis and hepatic immune tolerance remain unclear. Interleukin-27 (IL-27) has pro-inflammatory and anti-inflammatory functions among the cytokines that regulate immune responses. Its role in the liver microenvironment requires further investigation. Additionally, tissue-resident memory T cells (TRM) have been discovered in various organs in recent years, providing enhanced protection against subsequent infections. TRM cells expressing specific markers are also present in the liver. In our previous studies, it was found that IL-27 is expressed at higher levels compared to IL-10 and TGF-β in the livers in a mouse model of hepatitis B virus (HBV) infection. Therefore, we hypothesize that IL-27 may help maintain immune tolerance in the liver during viral infection. Additionally, previous studies have identified a group of CD8 T cells expressing asialoganglioside (ASGM1) that play an important role in acute hepatitis induced by HBV transfection and concanavalin A,and can back to the liver after transfered. Thus, this study aims to investigate the roles of IL-27 and ASGM1+ CD8 T cells in the liver immune microenvironment. The results show that HBV induces IL-27 production in the liver, and IL-27 levels are statistically significantly correlated with viral clearance. This IL-27 production leads to the expression of exhaustion markers on CD8 T cells and reduced interferon-γ production, thereby maintaining immune tolerance in the liver. The same results were observed after depleting macrophage lineage cells derived IL-27, indicating that IL-27 produced by macrophage lineage cells following HBV transfection maintains immune tolerance in the liver. Single-cell RNA sequencing analysis revealed that intrahepatic ASGM1+ CD8 T cells could be divided into different groups, with one group showing high expression of interferon-γ similar to TRM cells. Adoptive transfer experiments demonstrated that in vitro activated intrahepatic ASGM1+ CD8 T cells could promote hepatitis. ASGM1+ CD8 T cells play a pro-inflammatory role in the liver immune microenvironment. This study provides new insights into the liver microenvironment. Using a HBV transfection mouse model, we demonstrate that IL-27 maintains immune tolerance in the liver, suggesting its potential as a therapeutic target for HBV. Adoptive transfer experiments show that ASGM1+ CD8 T cells play a pro-inflammatory role in the liver immune microenvironment, indicating their potential to activate hepatic immune responses.