CD27 Ligand/CD70  

CD70 (CD27配体) 属于肿瘤坏死因子 (TNF) 家族，是 CD27 (TNFRSF27) 的配体^[1]。CD70 和 CD27 分别是同三聚体 II 型和同二聚体 I 型跨膜糖蛋白，分别表达于活化和静息的 T/B 淋巴细胞上^[2][3]。CD70 参与了肿瘤细胞和调节性 T 细胞的活性调节，激活先天免疫和适应性免疫。CD70 在成熟树突状细胞中表达，并在 CD40 或 Toll 样受体触发时上调^[4]。CD70 在动物疾病模型中有广泛应用，但其在人类中的氨基酸序列与小鼠和大鼠有很大的差异，两两序列的相似性分别为 56.25% 和 55.79%。CD70 是一系列弥漫性大B细胞淋巴瘤中最频繁突变的基因之一，尤其在爱泼斯坦-巴尔病毒 (EBV) 特异性 T 细胞免疫中起作用，更广泛地用于 B 细胞的免疫监视。CD70 能够恢复被缺乏 CD70 且 EBV 感染的 B 细胞刺激的 T 淋巴细胞的扩张来抑制 EBV 感染^[2]。CD70 还能够诱导共刺激 T 细胞增殖，增强细胞溶解性 T 细胞的生成，促进 T 细胞活化^[3]。据报道，CD70 还在调节 B 细胞活化、自然杀伤细胞的细胞毒性功能和免疫球蛋白合成中发挥作用^[5]。

CD70 (CD27 Ligand) belongs to the tumor necrosis factor (TNF) family, is the ligand for CD27 (TNFRSF27)^[1]. CD70 and CD27 are homotrimer type II and homodimer type I transmembrane glycoprotein, expressing on activated and resting T and B lymphocytes, respectively^[2][3]. CD70 involves in tumor cells and regulatory T cells survival, enabling activation of innate and adaptive immunity. CD70 expresses in the mature dendritic cells and is up-regulated upon the triggering of CD40 or Toll-like receptors^[4]. As for a wildly use of CD70 in animal disease model, the sequence of amino acids in human is very different from mouse (56.25%) and rat (55.79%). CD70 as one of the most frequently mutated genes in a series of diffuse large B cell lymphomas, especially acts in a crucial Epstein-Barr virus (EBV)-specific T cell immunity and more generally for the immune surveillance of B cells. CD70 inhibits EBV infection by restoring the expansion of EBV-specific T lymphocytes stimulated by the CD70-deficient EBV-infected B cells^[2]. CD70 induces proliferation of costimulated T cells, enhances the generation of cytolytic T cells, and contributes to T cell activation^[3]. CD70 is also reported to play a role in regulating B-cell activation, cytotoxic function of natural killer cells, and immunoglobulin sythesis^[5].

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