中药淫羊藿苷抑制肝癌HepG2.2.15细胞增殖和免疫逃逸作用研究

目的:观察中药淫羊藿苷(ICA)对HepG2.2.15细胞增殖及对CD3AK细胞杀伤活性的影响,探讨ICA对肝癌细胞Fas/FasL途径免疫逃逸的逆转作用,为ICA的开发应用提供新的理论和实验依据.方法:MTT法检测细胞增殖和细胞杀伤活性;流式细胞术检测细胞表面分子表达水平和细胞凋亡率.结果:50 μg/mlICA作用HepG2.2.15细胞48、72小时的增殖抑制作用明显,抑制率分别为22.04%、29.68%(P＜0.05),呈时间依赖效应.HepG2.2.15细胞经ICA处理后,FasL的表达率由16.22%显著下降至8.29%,Fas表达率由0.79%提高到1.70%(P＞0.05).ICA可明显抑制HepG2.2.15细胞诱导Jurkat细胞凋亡,凋亡率从46.66%下降为18.20%.ICA处理HepG2.2.15细胞后,不同效靶比的CD3AK细胞的杀伤活性,可分别由对照组的15.81%、35.04%、42.85%显著提高至42.58%、67.55%、88.93%(P＜0.05,P＜0.01),呈效靶比依赖效应.结论:ICA能有效地抑制HepG2.2.15细胞增殖,并有一定时间依赖效应;ICA可下调FasL的表达,上调细胞表面Fas的表达,对HepG2.2.15细胞诱导的T淋巴细胞凋亡作用有一定阻断,逆转肿瘤细胞的免疫逃逸作用;ICA显著增强HepG2.2.15细胞对CD3AK细胞杀伤的敏感性.     

Fas/FasL途径介导的人肺癌细胞免疫逃逸

目的：观察在3种人肺癌细胞（A549、EBC-1、LCSC）和人T细胞(Jurkat) Fas/FasL表达情况，探讨人肺癌细胞免疫逃逸及反杀伤作用与Fas/FasL途径的关系。 方法： 用FACScan、RT-PCR方法检测Fas/FasL蛋白及mRNA表达；以荧光染色法观察细胞调亡；用台盼蓝拒染法检测细胞存活。 结果： 3种人肺癌细胞及T-细胞系(Jurkat)均表达 Fas及 FasL；肺癌细胞与Jurkat细胞共培养时，肺癌细胞可导致Jurkat细胞生长抑制(P<0.05)及凋亡；在共培养体系中加入FasL中和性抗体NOK1，可封闭肺癌细胞对Jurkat细胞的生长抑制作用(P>0.05)。 结论： Fas/FasL途径可介导上述3种人肺癌细胞对Jurkat细胞的生长抑制及致凋亡作用；中和性抗体可有效阻断Fas信号转导途径，抑制肿瘤细胞的反杀伤作用，有效保护免疫系统。     

人参总皂苷和小檗碱对肺癌PG细胞"Fas反击"的影响

目的：探讨人参总皂苷（Ginsenosirde，Gs）和小檗碱（Berberine，Ber）对肿瘤“Fas反击”免疫逃逸机制的影响。方法：首先建立肺癌PG细胞与Jurkat细胞的共培养体系；Giemsa染色和流式细胞仪观察和检测共培养后的Jurkat细胞的凋亡；SABC免疫细胞化学法检测Gs和Ber处理后的PG细胞FasL、Fas分子的表达。结果：Jurkat细胞与PG细胞共培养后产生凋亡，Gs和Ber处理的PG细胞诱导的Jurkat细胞凋亡更为显著；Gs和Ber可以上调PG细胞FasL、Fas分子的表达。结论：Gs和Ber可以促进PG细胞诱导Jurkat细胞凋亡的作用，其机制可能与Gs和Ber上调PG细胞FasL分子的表达有关。     

特异性ASODN抑制Fas表达降低FasL介导细胞凋亡的研究

为了研究特异性Fas反义寡核苷酸(ASODN)对T细胞Fas表达及肝癌细胞诱导其凋亡的抑制作用,用脂质体介导法将Fas ASODN导入Jurkat T细胞,并通过用流式细胞术、RT-PCR及与肝癌细胞共培养方法研究Fas ASODN对T细胞Fas表达、Fas mRNA水平及凋亡的影响。结果显示:①Hep G2.2.15细胞表达有功能的FasL,可诱导Jurkat细胞凋亡;②Jurkat细胞转染Fas ASODN后,Fas mRNA降低;细胞表面Fas表达下降;与Hep G2.2.15细胞共培养后的凋亡率下降。表明Fas ASODN转染可以部分逆转肝癌细胞对T细胞的凋亡诱导作用。     

IFNγ调控人肺癌A549细胞Fas／FasL表达对T淋巴细胞生长的影响

为探讨IFNγ调控有肺癌细胞Fas/FasL表达对T细胞生长的影响，分别采用FACScan,RT-PCR方法检测Fas/FasL蛋白质及mRNA表达；以荧光染色及FACScan法观察细胞凋亡；用苔酚兰排除实验分析细胞生长。结果表明，人肺癌细胞A549及T－细胞系（Jurkat)均有Fas及FasL表达；IFNγ可引起A549Fas表达上调，且与剂量相关，并增加了A549细胞凋亡诱导的敏感性；A549细胞与Jurkat细胞共培养实验证明：人A549细胞通过Fas/FasL介导导致Jurkat细胞生长抑制及凋亡诱导；IFNγ处理A549细胞后，减少了其对Jurkat细胞的生长抑制。上述结果提示：Fas/FasL途径介导了A549细胞与Jurkat细胞之间的凋亡，IFNγ通过对人肺癌细胞Fas/FasL系统表达调控，使A549细胞自身对凋亡诱导的敏感性增加，并对T细胞生长的抑制作用减弱，提示IFNγ在防止肿瘤细胞逃避免疫监控有一定作用。     

CpG-ODN下调HeLa细胞功能性Fas配体的表达

为观察CpG-ODN对宫颈癌细胞系HeLa细胞Fas配体(FasL)表达水平的影响,探讨其对由HeLa细胞Fas-FasL途径诱导的淋巴细胞凋亡作用。采用实时荧光RT-PCR方法检测HeLa细胞、正常宫颈上皮细胞中FasL和Jurkat T淋巴细胞中Fas的表达水平,应用HeLa细胞与Jurkat细胞共培养的方法体外研究HeLa细胞FasL诱导T淋巴细胞凋亡作用。结果显示:①HeLa细胞、正常宫颈上皮细胞中FasL表达阳性,其表达水平分别是(0.99±0.05)、(0.68±0.03),差别具有统计学意义(P=0.0007);Jurkat细胞Fas表达呈阳性;②HeLa细胞与Jurkat细胞共培养后Jurkat细胞的凋亡率为(38.23%±4.98%),应用抗体NOK-2中和HeLa细胞的FasL后,Jurkat细胞凋亡率减少为(3.54%±1.61%),两者相比,差别有显著性意义(P=0.0001);③HeLa细胞用CpG-ODN处理前后FasL的表达水平分别是(0.99±0.05)、(0.79±0.04),差别有统计学意义(P=0.005);CpG-ODN预处理的HeLa细胞与Jurkat细胞共培养后Jurkat细胞凋亡率为(6.41%±2.81%),而没有用CpG-ODN预处理的HeLa细胞与Jurkat细胞共培养Jurkat细胞凋亡率为(29.23±6.85)%,二者的差别有统计学意义(t=13.39,P=0.006)。HeLa细胞可能通过表达FasL主动诱导T淋巴细胞凋亡从而在肿瘤的免疫逃逸中发挥作用,CpG-ODN可通过下调FasL的表达而减少肿瘤细胞主动诱导的T淋巴细胞凋亡。     

CD44反义寡核苷酸对肿瘤细胞表面抗原和对CD3AK杀伤敏感性的调节作用

目的：观察CD44反义寡核苷酸调节人低分化黏液腺胃癌MCC80-3细胞Fas分子和凋亡抵抗基因bcl-2的表达水平，提高免疫效应细胞杀伤敏感性的作用和机制。方法：RT-PCR法检测CD44、bcl-2mRNA的表达水平。MTT法检测CD3AK杀伤活性。流式细胞术检测细胞表面CD44及Fas、FasL蛋白表达水平。结果：CD44反义寡核苷酸（1.6μmol／L）处理后，明显地抑制MGC80-3细胞CD44mRNA和蛋白表达水平，在CD44配体低分子量透明质酸（HA）存在下，使MCC80-3表面下调的Fas分子显著增高，表达率从6．69％提高到16．81％（P〈0．01）。CD3AK对反义寡核苷酸处理的MGC80-3细胞杀伤活性显著增高，并呈效靶比依赖效应（P〈0．01）。MGC80-3细胞bcl-2mRNA的相对表达定量值由1．06降至0．32。结论：CD44反义寡核苷酸可通过抑制MGC80-3细胞CD44mRNA和蛋白表达，上调Fas分子的表达，下调凋亡抵抗基因bcl-2的表达，并提高其对免疫效应细胞的杀伤敏感性。     

层黏素受体靶向RNA干扰在削弱直肠癌免疫逃逸中的作用探讨

为探讨层黏素受体(laminin receptor,LNR)靶向RNA干扰在直肠癌免疫逃逸中的作用,将pGenesil-3-shLNR重组质粒转染SW480细胞,对比干扰组、对照组和空载组细胞中LNR mRNA和蛋白表达情况。建立SW480细胞与人Jurkat细胞Transwell小室旁分泌共培养模型,检测共培养48 h后SW480细胞和Jurkat细胞的凋亡率,并检测2种细胞Fas、FasL、Caspase-8 mRNA和蛋白表达情况。结果显示,重组质粒转染效率为(65.30±6.03)%。与对照组、空载组比较,干扰组LNR mRNA和蛋白相对表达量均较低(P0.05);SW480细胞凋亡率较高(P0.05),Jurkat细胞凋亡率较低(P0.05);SW480细胞Fas、Caspase-8 mRNA和蛋白相对表达量均较高,FasL mRNA和蛋白相对表达量较低,Jurkat细胞Fas、Caspase-8 mRNA和蛋白相对表达量均较低,FasL mRNA和蛋白相对表达量较高(P0.05)。对照组与空载组LNR mRNA及蛋白相对表达量,SW480细胞和Jurkat细胞凋亡率,SW480细胞和Jurkat细胞Fas、FasL、Caspase-8 mRNA及蛋白相对表达量比较,差异均无统计学意义(P 0.05)。以上结果提示LNR靶向RNA干扰可抑制直肠癌细胞中LNR表达,可能通过调节SW480细胞和Jurkat细胞中Fas/FasL信号通路使SW480细胞诱导Jurkat细胞凋亡率降低,同时增强Jurkat细胞杀伤SW480细胞能力,削弱直肠癌细胞的免疫逃逸能力。     

肝癌细胞系HEpG2表达FasL杀伤T淋巴细胞

为研究肝肿瘤细胞系表达FasL逃逸免疫监视的可能 ,采用逆转录 PCR方法和免疫组化法测肝癌细胞株FasL的表达 ,并测T淋巴细胞的凋亡。结果发现HEpG2细胞在mRNA水平和蛋白质水平上皆可检测到FasL的高表达 ,而 772 1细胞未能测到。HEpG2细胞与JurkatT淋巴细胞共培养后 ,19 4%的T细胞发生凋亡 ,抗FasL的单抗能阻断这种凋亡。因而肝肿瘤细胞HEpG2表达功能性的FasL ,能杀伤Fas阳性[1] 的T淋巴细胞。     

SLE患者外周血T细胞亚群凋亡特点及其相关机制的研究

目的:研究系统性红斑狼疮(SLE)患者外周血CD3+、CD4+、CD8+T细胞亚群的凋亡特点及其相关的凋亡机制。方法:采用三色荧光流式细胞术检测高活动性SLE患者、低/非活动性SLE患者以及正常对照者外周血T细胞亚群的百分比例、T细胞亚群膜表面Fas/FasL的表达率、T细胞亚群早期凋亡(AV+PI-)的情况;采用ABC-ELISA法测定各组SLE患者和正常对照者血清IL-10水平;对10例血清IL-10水平异常升高的高活动性SLE患者进行体外PBMCs培养实验,其中分别加入抗FasL抗体和抗IL-10抗体,48小时常规培养后分别检测PBMCs中T细胞亚群百分比例、T细胞亚群膜表面Fas/FasL的表达率、T细胞亚群早期凋亡的变化。结果:SLE患者外周血T细胞凋亡异常增多,其中以高活动性SLE患者CD4+T细胞亚群的凋亡尤为显著(P0.05),CD4+T细胞的异常凋亡与CD4+和CD8+T细胞膜表面表达增高的Fas/FasL密切相关(P0.05);各组SLE患者外周血血清IL-10水平均明显升高(P0.01),高活动性SLE患者更为明显,血清IL-10水平升高不仅与SLE主要临床检验指标相关,而且与CD4+/CD8+比值减少、CD4+T细胞高表达FasL相关(P0.05);随访研究显示,随着SLE病情好转、稳定,血清IL-10水平下降明显、T细胞亚群Fas/FasL的表达率明显减少、T细胞亚群凋亡逐渐减少,以上变化均在CD4+T细胞亚群中体现得最为明显(P0.05)。结论:SLE患者T细胞活动性异常升高,尤其是CD4+T细胞亚群凋亡增加,是SLE疾病发展的重要病理机制,IL-10作为能诱导T细胞高表达Fas/FasL的重要调节因子,参与了SLE患者CD4+T细胞凋亡的免疫调节,SLE患者异常增高的IL-10很可能通过Fas/FasL途径促进了T细胞尤其是CD4+T细胞亚群的凋亡。     

Suppression of FasL expression in tumor cells and preventing tumor necrosis factor-induced apoptosis by adenovirus 14.7K is an effective escape mechanism for immune cells

To elucidate if the Fas/FasL signal pathway participates in the immune escape of tumor cells, and if contemporary Fas/FasL and tumor necrosis factor (TNF))-induced apoptosis is better for immune cell survival than just blocking Fas/FasL-induced apoptotic signal. FasL expression in mouse H22 hepatocellular cancer cells was suppressed by the siRNA technique. The wild-type Ad5 14.7K gene was amplified by polymerase chain reaction and transduced into Jurkat T-cells. Apoptosis of target Jurkat cells was detected by flow cytometry. TNF-alpha in the culture supernatant of H22 cells by ELISA was seen. FasL and 14.7K gene expression in stably transfected or transduced clones were determined by Western blotting. As a result, FasL expression in H22 cells was down-regulated after stable transfection with a plasmid encoding antisense FasL cDNA. Down-regulation of FasL expression in H22 cells had no effect on tumor growth in vitro. There was an apparent decrease in the number of apoptotic Jurkat T-cells after coculture with transfected H22 cells, relative to coculture with FasL-expressing untransfected cells. Compared with untransduced Jurkat cells, apoptotic rates in 14.7K-transduced Jurkat cells were significantly reduced in three different E/T ratios (P < 0.01), respectively. We conclude that Fas/FasL signal pathway participates in the immune escape of tumor cells by inducing immune cells apoptosis. Reducing the expression of FasL in tumor cells can decrease the apoptotic rate of immune cells, further blocking the apoptotic signal pathway of immune cells by preventing TNF-induced apoptosis can increase the survival of immune cells.     

转染反义Fas阻断T细胞凋亡及对肿瘤的治疗意义

目的 通过阻断Ｔ细胞的Ｆａｓ信号传递途径,探讨消除肿瘤对Ｔ细胞的攻击及其对肿瘤的治疗意义。方法 流式细胞术、ＲＴ－ＰＣＲ方法检测卵巢癌细胞表达Ｆａｓ和ＦａｓＬ。构建ｐｃＤＮＡ３－反义Ｆａｓ真核表达载体,经脂质体转染Ｊｕｒｋａｔ细胞,流式细胞仪检测Ｆａｓ表达变化。以Ａｎｎｅｘｉｎ－Ｖ和ＭＴＴ法检测转染反义Ｆａｓ基因对Ｊｕｒｋａｔ细胞凋亡的影响。采用ＭＴＴ体外杀伤实验观察３ＡＯ对Ｊｕｒｋａｔ细胞杀伤变化。结果 ６种卵巢癌细胞均表达Ｆａｓ和ＦａｓＬ。ｐｃＤＮＡ３－反义Ｆａｓ基因可以使Ｊｕｒｋａｔ细胞表达Ｆａｓ量下降并部分阻断Ｆａｓ单抗诱导的Ｊｕｒｋａｔ细胞凋亡,３ＡＯ对其杀伤减弱。结论 卵巢癌细胞表达ＦａｓＬ可能是其逃逸免疫监视并产生对淋巴细胞攻击的原因之一;应用反义技术阻断Ｆａｓ表达,可部分阻断Ｆａｓ单抗诱导Ｊｕｒ     

Expression of functional Fas ligand in choriocarcinoma

PROBLEM: In the course of pregnancy, fetal trophoblast cells and in that of choriocarcinoma-etiology, trophoblast derived tumor cells, invade the uterine mucosa without causing rejection by decidual leukocytes. Fas ligand (FasL, CD95L, APO-IL), a central regulator of the immune system, has been implicated in the maintenance of immune privileged sites, such as the eye, the testis and the pregnant uterus by inducing apoptosis in activated infiltrating leukocytes. In normal pregnancy FasL, which is expressed by trophoblast cells, appears to contribute to the immune privilege of the pregnant uterus. As choriocarcinoma derives from trophoblast we wanted to assess the expression of FasL in this tissue. METHOD OF STUDY: Immunohistochemistry, immunofluorescence, TUNEL-assay, Western blotting, coculture experiments and flourescence-associated cell sorter-analysis were the techniques used. RESULTS: Expression of FasL was found on cells of choriocarcinoma in paraffin sections in situ and on three choriocarcinoma cell lines such as JEG-3, JAR and BeWo. These results were confirmed by Western blotting. In coculture experiments choriocarcinoma cells induced apoptosis in a Jurkat cell line - sensitive to FasL mediated killing. However, when the Jurkat cells were pre-incubated with a Fas-blocking monoclonal antibody, apoptosis was abolished to a great extent. CONCLUSION: Our findings show that choriocarcinoma cells express FasL and this aforementioned molecule is biologically active. We assume that FasL expression on choriocarcinoma cells may contribute to control of anti-tumor responses by inducing apoptosis in activated Fas bearing leukocytes.     

Apoptosis induced in T cells by human neuroblastoma cells: role of Fas ligand

The CD95/CD95L (Fas/Fas ligand) receptor/ligand system plays an important role in regulation of cell survival and induction of a programmed cell death. It is also involved in regulation of effector phase of T and NK cell cytotoxicity, establishment of immune privilege sites, and tumor escape from immune recognition. In this study, we assessed expression of CD95L in tumors obtained from patients with neuroblastoma (NB) and in established NB cell lines. We measured the presence of intratumoral T cell infiltrates and T cell survival in tumor tissue samples. High levels of apoptosis were observed in tumor-associated lymphocytes as well as in Jurkat T cells cocultured with NB cells in vitro. T cell death was reduced after treatment of NB cells (in vitro) with antibody to FAS ligand (FasL). Overall, our data suggest that NB-induced apoptosis of Fas-sensitive Jurkat T cells is mediated by functional FasL expressed on NB and Fas/FasL interaction may be responsible for the elimination of T cells in the NB microenvironment.     

Death of solid tumor cells induced by fas ligand expressing primary myoblasts

Anticancer therapy for solid tumors suffers from inadequate methods for the localized administration of cytotoxic agents. Fas ligand (FasL) has been reported to be cytotoxic to a variety of cells, including certain tumor cell lines. We therefore postulated that myoblasts could serve as non-transformed gene therapy vehicles for the continuous localized delivery of cytotoxic anticancer agents such as FasL. However, contrary to previous reports, fluorescence activated cell sorting (FACS) analyses revealed that both primary mouse and human myoblasts express Fas, the receptor for FasL. To avoid self-destruction and test the cytotoxic potential of myoblasts, the cells were isolated from mice deficient in Fas (lpr/lpr), the mouse counterpart of human autoimmune lymphoproliferative syndrome (ALPS). These primary mouse myoblasts were transduced with a retroviral vector encoding mouse FasL and expression of a biologically active and soluble form of the molecule was confirmed by the apoptotic demise of cocultured Fas-expressing Jurkat cells, the standard in the field. To test whether the lpr myoblasts expressing FasL could be used in anticancer therapy, human rhabdomyosarcoma derived cell lines were assayed for Fas and then tested in the apoptosis coculture assay. The majority of Fas-expressingmuscle tumor cells were rapidly killed. Moreover, FasL expressing myoblasts were remarkably potent; indeed well characterized cytotoxic antibodies to Fas were only 20% as efficient at killing rhabdomyosarcoma cells as FasL expressing myoblasts. These findings together with previous findings suggest that primary myoblasts, defective in Fas but genetically engineered to express FasL, could function as potent anticancer agents for use in the localized destruction of solid tumors in vivo by three synergistic mechanisms: (1) directly via Fas/FasL mediated apoptosis, (2) indirectly via neutrophil infiltration and immunodestruction, and (3) as allogeneic inducers of a bystander effect via B and T cells.     

ICA和PJA对高转移性人肺癌细胞体外侵袭转移能力抑制的研究

目的：将新型抗癌药物淫羊藿甙（ＩＣＡ）和济南假单胞菌制剂（ＰＪＡ）作用于ＰＧ细胞,从肿瘤转移抑制的多个方面和环节探讨ＰＪＡ、ＩＣＡ抗转移作用的机制。方法：采用粘附实验、运动侵袭实验、逆转录ＰＣＲ（ＲＴ－ＰＣＲ）、细胞免疫组化等多种方法进行了检测。结果：ＰＪＡ、ＩＣＡ可降低ＰＧ细胞对胞外基质的粘附性及侵袭、运动能力,减少ＰＧ细胞表面粘附分子ＣＤ４４Ｖ６、ＬＮ－Ｒ及胞浆内ＣＫ１８的表达,同时细胞内ｃ－ｍｙｃ、Ｔｉａｍ－１基因ｍＲＡＮ水平均有不同程度的降低,而Ｎｍ２３－Ｈ１ ｍＲＮＡ水平有不同程度的升高,且两药有明显的协同作用。结论：ＰＪＡ、ＩＣＡ通过对肿瘤转移多个步骤的抑制而发挥抗转移作用。     

Activation through CD40 ligation induces functional Fas ligand expression by Langerhans cells

Langerhans cells (LC) are professional antigen-presenting cells of dendritic cell (DC) lineage and are critical for the induction of primary immune responses in skin. Following antigenic stimulation, LC migrate to regional lymph nodes and induce antigen-specific activation of T cells. After primary expansion, the majority of T cells undergo Fas/Fas ligand (FasL)-mediated apoptotic cell death, thereby suppressing their excessive expansion. Although recent investigations have indicated an immunoregulatory function for DC, whether LC could be involved in Fas/FasL-mediated suppression of activated T cells is still unclear. In this study, we found that LC express FasL after activation triggered through CD40 molecules on their surface, but not by stimulation with LPS or IFN-gamma. The functional significance of FasL expression by LC was demonstrated using two different assays for apoptosis induced in Jurkat cells. The apoptosis in Jurkat cells was completely blocked by anti-FasL blocking antibody, suggesting a Fas/FasL-mediated mechanism. These results indicate a new feedback mechanism to down-regulate T cell activation by LC through the interaction of the TNF receptor/ligand superfamily, CD40/CD40L and Fas/FasL.     

Expression of Fas and Fas ligand and apoptosis in tumor-associated lymphocytes and in tumor cells from malignant pleural effusions

The CD95 (APO-1/Fas)-Fas ligand (FasL) system is an important mediator of antitumor T cell cytotoxicity. The aim of the current study was to assess its significance in human cancer. Malignant effusions were selected as an environment allowing direct cell-to-cell contact in a fluid phase. Malignant pleural effusions collected from 23 patients with metastatic carcinoma of the bronchus, ovary, stomach or breast were examined by means of flow cytometry. The expression ofFas and FasL, probed with the appropriate antibodies, apoptosis of tumor cells and the characteristics of tumor-associated lymphocytes (TAL) were determined by TUNEL reaction in malignant and nonmalignant (control) effusions. All malignant cells had partially or completely lost the expression of CD95 and expressed an elevated level of FasL. In contrast, TAL obtained from malignant pleural effusions demonstrated a marked decrease in the expression of surface FasL and an increase in surface-bound Fas. The percentage of apoptotic malignant cells was significantly decreased, as compared to TAL and lymphocytes from nonmalignant pleural effusions. There were also differences in the expression of Fas and FasL among mononuclear cells from malignant and nonmalignant pleural effusions. The ability of TAL from malignant pleural effusions to induce apoptosis of K562 cells was diminished, as compared to peripheral blood lymphocytes. Taken together, these data suggest that tumor cells in the microenvironment of malignant pleural effusions can evade immune attack by downregulation of the CD95 receptor and by killing lymphocytes through the expression of FasL. These results confirm earlier reports which showed that lymphocytes from a tumor microenvironment appear to have a depressed cytotoxic action.