Xu Junfa, Huang Baojun, Xiong Ping, Feng Wei, Xu Yong, Fang Min, Zheng Fang, Gong Feili
Department of Immunology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, China.
Cell Mol Immunol. 2006 Jun;3(3):235-40.
B7-H3 is a recently identified member of the B7 gene family. Its ubiquitous expression in both lymphoid and nonlymphoid tissues suggests that it could play an important role in the maintenance of self-tolerance. However, the exact function of B7-H3 is still elusive. The purpose of current study is to demonstrate the possible function of soluble mouse B7-H3 for prevention of DC-mediated T cell activation. For this purpose, we established a soluble mouse B7-H3 fusion protein (mB7h3-hIg) eukaryotic expression vector (pmB7h3-hIg) with a C-terminal human IgG1 Fc. A C57BL/6 (B6)-derived dendritic cell line (DC2.4 cells) was used for the establishment of stable transfectants for generation of soluble mB7h3-hIg. Ectopic mB7h3-hIg expression was confirmed by RT-PCR, Western blot and ELISA analyses. A 49.7 kD protein was detected by Western blot from DC2.4 cells transfected with pmB7h3-hIg. It was found that soluble mB7h3-hIg expression has no effect on cell cycling and apoptosis and the expression of CD80 and CD86 of the DC2.4 cells. However, ectopic soluble mB7h3-hIg expression was found to significantly affect the allo-stimulatory capability for DC2.4 cells. DC2.4 cells expressing soluble mB7h3-hIg showed a significant reduced allo-stimulatory capability as compared with the controls determined by MLC. Further studies revealed that soluble mB7h3-hIg could also inhibit IL-2 and IFN-gamma production of allogenic T cells. These results suggested a great potential of soluble B7-H3 for treatment of graft rejection and autoimmume disease.
B7-H3是B7基因家族中最近发现的成员。它在淋巴组织和非淋巴组织中普遍表达，这表明它可能在维持自身耐受性方面发挥重要作用。然而，B7-H3的确切功能仍然不清楚。本研究的目的是证明可溶性小鼠B7-H3在预防树突状细胞（DC）介导的T细胞活化中的可能功能。为此，我们构建了一个带有C端人IgG1 Fc的可溶性小鼠B7-H3融合蛋白（mB7h3-hIg）真核表达载体（pmB7h3-hIg）。使用源自C57BL/6（B6）的树突状细胞系（DC2.4细胞）来建立稳定转染子，以产生可溶性mB7h3-hIg。通过RT-PCR、蛋白质印迹和ELISA分析证实了异位mB7h3-hIg的表达。蛋白质印迹法从用pmB7h3-hIg转染的DC2.4细胞中检测到一种49.7 kD的蛋白质。发现可溶性mB7h3-hIg的表达对DC2.4细胞的细胞周期、凋亡以及CD80和CD86的表达没有影响。然而，发现异位可溶性mB7h3-hIg的表达显著影响DC2.4细胞的同种异体刺激能力。与通过混合淋巴细胞培养（MLC）测定的对照相比，表达可溶性mB7h3-hIg的DC2.4细胞显示出显著降低的同种异体刺激能力。进一步的研究表明，可溶性mB7h3-hIg还可以抑制同种异体T细胞产生白细胞介素-2（IL-2）和γ干扰素（IFN-γ）。这些结果表明可溶性B7-H3在治疗移植排斥和自身免疫性疾病方面具有巨大潜力。
