Behrens C K, Igney F H, Arnold B, Möller P, Krammer P H
Tumor Immunology Program, German Cancer Research Center, Heidelberg, Germany.
J Immunol. 2001 Mar 1;166(5):3240-7. doi: 10.4049/jimmunol.166.5.3240.
CD95 (APO-/Fas) ligand (CD95L) is a member of the TNF family predominantly expressed by activated T and NK cells but also by tumors of diverse cellular origin. CD95L trimerizes surface CD95 expressed by target cells that subsequently undergo apoptosis. The role of the CD95/CD95L system in the down-regulation of an immune response (activation-induced cell death) is established. However, it is so far unclear why tumors express CD95L. To investigate whether tumors use the CD95L to down-regulate an anti-tumor immune response, we established a transgenic (tg) mouse model consisting of 1) apoptosis-resistant tumor cells, designated LKC-CD95L, which express functional CD95L and the model tumor Ag K(b); and 2) perforin knockout (PKO) anti-K(b) TCR tg mice. L1210-Fas antisense expressing K(b), crmA, and CD95L (LKC-CD95L) killed CD95(+) unrelated tumor targets and Con A-activated splenocytes from anti-K(b) TCR tg PKO mice by a CD95L-dependent mechanism in vitro. However, we could not detect any cytotoxic activity against anti-tumor (anti-K(b)) T cells in vivo. We also observed reduced growth of LKC-CD95L in nude mice and rapid rejection in anti-K(b) TCR tg PKO mice. Because the tumor cells are resistant to CD95L-, TNF-alpha-, and TNF-related apoptosis-inducing ligand-induced apoptosis and the mice used are perforin-deficient, the involvement of these four cytotoxicity mechanisms in tumor rejection can be excluded. The histological examination of tumors grown in nude mice showed infiltration of LKC-CD95L tumors by neutrophils, whereas L1210-Fas antisense expressing K(b) and crmA (LKC) tumor tissue was neutrophil-free. Chemotaxis experiments revealed that CD95L has no direct neutrophil-attractive activity. Therefore, we conclude that LKC-CD95L cells used an indirect mechanism to attract neutrophils that may cause tumor rejection.
CD95（APO-/Fas）配体（CD95L）是肿瘤坏死因子（TNF）家族的成员之一，主要由活化的T细胞和自然杀伤（NK）细胞表达，但也可由多种细胞来源的肿瘤表达。CD95L可使靶细胞表面表达的CD95三聚化，进而使靶细胞发生凋亡。CD95/CD95L系统在下调免疫反应（激活诱导的细胞死亡）中的作用已得到证实。然而，目前尚不清楚肿瘤为何表达CD95L。为了研究肿瘤是否利用CD95L下调抗肿瘤免疫反应，我们建立了一种转基因（tg）小鼠模型，该模型由以下两部分组成：1）抗凋亡肿瘤细胞，命名为LKC-CD95L，其表达功能性CD95L和模型肿瘤抗原K(b)；2）穿孔素基因敲除（PKO）的抗K(b) TCR转基因小鼠。表达K(b)、crmA和CD95L的L1210-Fas反义基因（LKC-CD95L）在体外通过依赖CD95L的机制杀死CD95(+)无关肿瘤靶细胞以及来自抗K(b) TCR转基因PKO小鼠的刀豆蛋白A激活的脾细胞。然而，我们在体内未检测到针对抗肿瘤（抗K(b)）T细胞的任何细胞毒性活性。我们还观察到LKC-CD95L在裸鼠中的生长减缓以及在抗K(b) TCR转基因PKO小鼠中被快速排斥。由于肿瘤细胞对CD95L、肿瘤坏死因子-α（TNF-α）和肿瘤坏死因子相关凋亡诱导配体诱导的凋亡具有抗性，且所用小鼠缺乏穿孔素，因此可以排除这四种细胞毒性机制参与肿瘤排斥反应。对裸鼠体内生长的肿瘤进行组织学检查发现，LKC-CD95L肿瘤有中性粒细胞浸润，而表达K(b)和crmA的L1210-Fas反义基因（LKC）肿瘤组织则无中性粒细胞浸润。趋化实验表明，CD95L没有直接吸引中性粒细胞的活性。因此，我们得出结论，LKC-CD95L细胞利用间接机制吸引中性粒细胞，这可能导致肿瘤排斥。
