Division of Gastroenterology, Hepatology, and Endoscopy, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115;
Department of Medicine I, University Medical Center Dresden, Technical University Dresden, 01307 Dresden, Germany.
Proc Natl Acad Sci U S A. 2017 Sep 26;114(39):10449-10454. doi: 10.1073/pnas.1701428114. Epub 2017 Sep 11.
Invariant natural killer T (iNKT) cells recognize lipid antigens presented by CD1d and play a central role in regulating immunity and inflammation in peripheral tissues. However, the mechanisms which govern iNKT cell homeostasis after thymic emigration are incompletely understood. Here we demonstrate that microsomal triglyceride transfer protein (MTP), a protein involved in the transfer of lipids onto CD1d, regulates liver iNKT cell homeostasis in a manner dependent on hepatocyte CD1d. Mice with hepatocyte-specific loss of MTP exhibit defects in the function of CD1d and show increased hepatic iNKT cell numbers as a consequence of altered iNKT cell apoptosis. Similar findings were made in mice with hepatocyte-specific loss of CD1d, confirming a critical role of CD1d in this process. Moreover, increased hepatic iNKT cell abundance in the absence of MTP is associated with susceptibility to severe iNKT cell-mediated hepatitis, thus demonstrating the importance of CD1d-dependent control of liver iNKT cells in maintaining immunological homeostasis in the liver. Together, these data demonstrate an unanticipated role of parenchymal cells, as shown here for hepatocytes, in tissue-specific regulation of CD1d-restricted immunity and further suggest that alterations in lipid metabolism may affect iNKT cell homeostasis through effects on CD1d-associated lipid antigens.
不变自然杀伤 T(iNKT)细胞识别由 CD1d 呈递的脂质抗原,并在调节外周组织的免疫和炎症中发挥核心作用。然而,iNKT 细胞在离开胸腺后的自我平衡机制尚未完全清楚。在此,我们证明微粒体甘油三酯转移蛋白(MTP),一种参与脂质转移到 CD1d 的蛋白,以依赖于肝细胞 CD1d 的方式调节肝脏 iNKT 细胞的自我平衡。肝细胞特异性缺失 MTP 的小鼠表现出 CD1d 功能缺陷,并由于 iNKT 细胞凋亡改变而导致肝脏 iNKT 细胞数量增加。在肝细胞特异性缺失 CD1d 的小鼠中也发现了类似的发现,证实了 CD1d 在这一过程中的关键作用。此外,在缺乏 MTP 的情况下,肝脏 iNKT 细胞的丰富度增加与严重的 iNKT 细胞介导的肝炎易感性有关,因此证明了 CD1d 依赖性控制肝脏 iNKT 细胞在维持肝脏免疫平衡中的重要性。总之,这些数据表明,实质细胞(如本文中的肝细胞)在组织特异性调节 CD1d 限制免疫方面发挥了意想不到的作用,并进一步表明脂质代谢的改变可能通过影响与 CD1d 相关的脂质抗原来影响 iNKT 细胞的自我平衡。
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