[The progress of studying the mechanisms of immune cells in the regulation of non-alcoholic fatty liver diseases].

Non-alcoholic fatty liver diseases (NAFLD) are liver diseases which are strongly associated with obesity. The incidence of NAFLD has been gradually increased in recent years. According to different pathology of the liver, NAFLD include three disease states: simple fatty liver, hepatitis (nonalcoholic steatohepatitis, NASH) and fatty liver cirrhosis. The accumulations of fat around the internal organs, which secrete a wide range of adipokines, such as interleukin-6, contribute the development and progress of NAFLD in obesity. In addition, the liver has been recognized as an immune organ containing several immune cells, for instance, inherited macrophages in the live (kupffer cells), nature killer cells, T lymphocytes, T regulatory cells (Tregs), myeloid-derived suppressor cells (MDSCs), and dendritic cells. These immune cells secret a number of cytokines, such as tumor necrosis factor (TNF-α) and monocyte chemoattractant protein (MCP-1), play important roles in the development of NAFLD. Moreover, a high level of fatty acids in the liver microenvironment, leads to suppress CD4(+)T cells and the loss of CD4(+)T cells in the microenvironment of the liver may be one of key factors which is associated with the progress of NAFLD to cirrhosis and liver cancer. This article aims to review the recent studies in the mechanisms of these immune cells involving in the progress of NAFLD, and to explore the novel strategies targeting these immune cells to control the prevalence of NAFLD and reduce liver fibrosis.非酒精性脂肪性肝病（NAFLD）是一类与肥胖相关的代谢性疾病，其发病率有逐年升高的趋势。根据肝脏病理学形态的不同，目前包括单纯性脂肪肝，脂肪性肝炎和脂肪性肝硬化3个疾病状态。肥胖导致脂肪组织在内脏器官周围堆积，脂肪细胞分泌脂肪因子的增加（如白细胞介素6）与NAFLD的发生、发展密切相关。另外，肝脏也被认为是一个重要的免疫器官，含有肝脏内固有的巨噬细胞（枯否细胞）,自然杀伤细胞，T淋巴细胞,调节性T淋巴细胞,髓源抑制性细胞及树突状细胞等免疫细胞。这些免疫细胞通过分泌一些重要的细胞因子，如肿瘤坏死因子和单核细胞趋化蛋白等参与了NAFLD及非酒精性脂肪性肝炎发生、发展过程中的炎症反应。肝脏局部微环境中高水平的脂肪酸通过抑制肝脏组织中CD4(+)T淋巴细胞，使CD4(+)T淋巴细胞在肝脏微环境中的缺失也可能是NAFLD进展为肝硬化及肝细胞肝癌的重要免疫调控异常的因素之一。免疫细胞还可以通过调控肝星状细胞的活化，影响肝纤维化的发生。现通过回顾这些免疫细胞在NAFLD过程中作用机制的研究，以期为临床探索控制NAFLD的进展，减轻肝脏纤维化提供治疗方向。.