Kasahara Senji, Ando Kazuki, Saito Kuniaki, Sekikawa Kenji, Ito Hiroyasu, Ishikawa Tetsuya, Ohnishi Hiroo, Seishima Mitsuru, Kakumu Shinichi, Moriwaki Hisataka
First Department of Internal Medicine, Gifu University School of Medicine, 40 Tsukasa-machi, Gifu 500-8705, Japan.
J Virol. 2003 Feb;77(4):2469-76. doi: 10.1128/jvi.77.4.2469-2476.2003.
Recent studies have shown that tumor necrosis factor alpha (TNF-alpha) plays critical roles in not only viral clearance but also lymphoid tissue development and stem cell differentiation. In this study, we attempted to induce hepatitis B virus (HBV)-specific cytotoxic T lymphocytes (CTLs) by immunization of TNF-alpha knockout (TNF-alpha(-/-)) mice with HBsAg-encoding plasmid DNA. An immunization with the HBV plasmid failed to induce CTL responses in TNF-alpha(-/-) mice, although CTLs were readily induced in wild-type mice by the same protocol. Weak CTL responses were produced in TNF-alpha(-/-) mice after two sessions of immunization with the HBV plasmid; however, TNF-alpha was required to maintain the responses of these CTL lines to in vitro stimulation and, even then, the responses were lost after 3 weeks. Interestingly, a limiting dilution of a CTL line showed that HBV-specific CTL clones with high specific cytotoxicity were present in TNF-alpha(-/-) mice, but these clones again failed to proliferate for more than 3 weeks. Furthermore, since exogenously added TNF-alpha enhanced the proliferation of a TNF-alpha(-/-) clone but suppressed that of a TNF-alpha(+/+) clone in vitro, TNF-alpha also has a direct effect on the proliferation of CTLs. In conclusion, TNF-alpha is essential rather than important for the proliferation of HBV-specific CTLs both in vivo and in vitro and this effect is not only due to the activation of dendritic cells but is also induced by the direct effect on CTLs.
最近的研究表明，肿瘤坏死因子α（TNF-α）不仅在病毒清除中起关键作用，而且在淋巴组织发育和干细胞分化中也起关键作用。在本研究中，我们试图通过用编码乙肝表面抗原（HBsAg）的质粒DNA免疫TNF-α基因敲除（TNF-α(-/-)）小鼠来诱导乙肝病毒（HBV）特异性细胞毒性T淋巴细胞（CTL）。尽管相同方案能在野生型小鼠中轻易诱导出CTL，但用HBV质粒免疫未能在TNF-α(-/-)小鼠中诱导出CTL反应。用HBV质粒对TNF-α(-/-)小鼠进行两轮免疫后产生了微弱的CTL反应；然而，TNF-α是维持这些CTL系对体外刺激反应所必需的，即便如此，3周后反应仍消失。有趣的是，对一个CTL系进行有限稀释显示，TNF-α(-/-)小鼠中存在具有高特异性细胞毒性的HBV特异性CTL克隆，但这些克隆同样未能增殖超过3周。此外，由于体外添加的TNF-α增强了TNF-α(-/-)克隆的增殖，但抑制了TNF-α(+/+)克隆的增殖，所以TNF-α对CTL的增殖也有直接影响。总之，TNF-α对于体内外HBV特异性CTL的增殖至关重要而非仅仅是重要，并且这种作用不仅归因于树突状细胞的激活，还由对CTL的直接作用诱导产生。
