Abstract：
Liver is the largest internal organ of the body with vital functions. In addition to its endocrine and exocrine activities, liver also plays a pivotal role in the immune system, including haematopoietic functions. Liver parenchymal cells, which are epithelial cells, have been found to possess innate immune functions by expressing pattern-recognition receptors (PRRs), producing complement components, and secreting cytokines. Intriguingly, in recent years, it has been discovered that liver epithelial cells also produce immunoglobulins (Igs), which have long been thought to be produced exclusively by B cells. Notably, even liver epithelial cells from B lymphocyte-deficient mice, including SCID mice and μMT mice, could also produce Igs. Compelling evidence has revealed both the physiological and pathological functions of liver-derived Igs. For instance, liver epithelial cells-derived IgM can serve as a source of natural and specific antibodies that contribute to innate immune responses, while liver-produced IgG can act as a growth factor to promote cell proliferation and survival in normal hepatocytes and hepatocarcinoma. Similar to that in B cells, the toll-like receptor 9 (TLR9)-MyD88 signaling pathway is also actively involved in promoting liver epithelial cells to secrete IgM. Liver-derived Igs could potentially serve as biomarkers, prognostic indicators, and therapeutic targets in the clinical setting, particularly for liver cancers and liver injury. Nevertheless, despite significant advances, much remains unknown about the mechanisms governing Ig transcription in liver cells, as well as the detailed functions of liver-derived Igs and their involvement in diseases and adaptive immunity. Further studies are still needed to reveal these underlying, undefined issues related to the role of liver-derived Igs in both immunity and diseases.
摘要：
肝脏是人体最大的内脏器官，具有重要功能。除了它的内分泌和外分泌活动，肝脏在免疫系统中也起着举足轻重的作用,包括造血功能。肝实质细胞,是上皮细胞，已发现通过表达模式识别受体（PRR）具有先天免疫功能，产生补体成分，分泌细胞因子.有趣的是，近年来,已经发现肝上皮细胞也产生免疫球蛋白（Igs），长期以来一直被认为是由B细胞产生的。值得注意的是,甚至来自B淋巴细胞缺陷小鼠的肝上皮细胞，包括SCID小鼠和μMT小鼠，也可以产生Igs。令人信服的证据揭示了肝脏衍生的Ig的生理和病理功能。例如,肝脏上皮细胞衍生的IgM可以作为天然和特异性抗体的来源，有助于先天免疫反应，而肝脏产生的IgG可以作为生长因子促进正常肝细胞和肝癌的细胞增殖和存活。类似于B细胞，Toll样受体9(TLR9)-MyD88信号通路也积极参与促进肝上皮细胞分泌IgM。肝脏衍生的Igs可能作为生物标志物，预后指标，和临床上的治疗目标，特别是肝癌和肝损伤。然而，尽管取得了重大进展，关于肝细胞中控制Ig转录的机制仍然未知，以及肝源性Ig的详细功能及其在疾病和适应性免疫中的参与。仍然需要进一步的研究来揭示这些潜在的，与肝脏衍生的Ig在免疫和疾病中的作用有关的未定义问题。
