Natural killer cells regulate T cell immune responses in primary biliary cirrhosis

Shinji Shimoda, Satomi Hisamoto, Kenichi Harada, Sho Iwasaka, Yong Chong, Minoru Nakamura, Yuki Bekki, Tomoharu Yoshizumi, Ken Shirabe, Toru Ikegami, Yoshihiko Maehara, Xiao Song He, M. Eric Gershwin, Koichi Akashi

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Abstract

The hallmark of primary biliary cirrhosis (PBC) is the presence of autoreactive T- and B-cell responses that target biliary epithelial cells (BECs). Biliary cell cytotoxicity is dependent upon initiation of innate immune responses followed by chronic adaptive, as well as bystander, mechanisms. Critical to these mechanisms are interactions between natural killer (NK) cells and BECs. We have taken advantage of the ability to isolate relatively pure viable preparations of liver-derived NK cells, BECs, and endothelial cells, and studied interactions between NK cells and BECs and focused on the mechanisms that activate autoreactive T cells, their dependence on interferon (IFN)-γ, and expression of BEC major histocompatibility complex (MHC) class I and II molecules. Here we show that at a high NK/BEC ratio, NK cells are cytotoxic for autologous BECs, but are not dependent on autoantigen, yet still activate autoreactive CD4+ T cells in the presence of antigen presenting cells. In contrast, at a low NK/BEC ratio, BECs are not lysed, but IFN-γ production is induced, which facilitates expression of MHC class I and II molecules on BEC and protects them from lysis upon subsequent exposure to autoreactive NK cells. Furthermore, IFN-γ secreted from NK cells after exposure to autologous BECs is essential for this protective function and enables autoreactive CD4+ T cells to become cytopathic. Conclusions: NK cell-mediated innate immune responses are likely critical at the initial stage of PBC, but also facilitate and maintain the chronic cytopathic effect of autoantigen-specific T cells, essential for progression of disease.

Original languageEnglish
Pages (from-to)1817-1827
Number of pages11
JournalHepatology
Volume62
Issue number6
DOIs
Publication statusPublished - Dec 1 2015

All Science Journal Classification (ASJC) codes

  • Hepatology

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    Shimoda, S., Hisamoto, S., Harada, K., Iwasaka, S., Chong, Y., Nakamura, M., Bekki, Y., Yoshizumi, T., Shirabe, K., Ikegami, T., Maehara, Y., He, X. S., Gershwin, M. E., & Akashi, K. (2015). Natural killer cells regulate T cell immune responses in primary biliary cirrhosis. Hepatology, 62(6), 1817-1827. https://doi.org/10.1002/hep.28122