黄芪皂苷钠治疗后烫伤鼠肺组织细胞凋亡及Fas／FasL的表达

目的探讨黄芪皂苷治疗后烫伤鼠肺组织细胞凋亡及基因调控变化机制,为进一步阐明烫伤鼠肺组织细胞凋亡机制和在细胞凋亡水平防治烧伤后脏器损伤提供理论依据.方法采用Tunel法及免疫组化技术观察黄芪皂苷治疗后烫伤鼠肺组织细胞凋亡,同时测定肺组织Fas/FasL的表达的变化.结果鼠烫伤后肺组织细胞凋亡明显增加,表现为肺泡上皮细胞和肺血管内皮细胞凋亡增加(P＜0.05);Fas抗原、FasL在烫伤鼠肺组织表达明显上调(P＜0.01),Fas抗原、FasL表达的增加与肺组织细胞凋亡增加呈平行关系;用黄芪皂苷治疗后凋亡明显减少,Fas抗原、FasL表达减弱.结论黄芪皂苷治疗后可在一定程度上防治烫伤鼠肺泡上皮和肺血管内皮细胞凋亡,其机理可能与Fas/FasL系统参与有关.     

急性呼吸窘迫综合征患者肺组织Fas/FasL系统表达的变化及其意义

目的：探讨细胞凋亡在急性呼吸窘迫综合征（ＡＲＤＳ）发病中的作用及基因调控机制,为进一步阐明ＡＲＤＳ的发病机制和在细胞凋亡水平防治本病提供理论依据。方法：ＡＲＤＳ组９例,对照组５例,采用ＴＵＮＥＬ法以及免疫组化技术观察ＡＲＤＳ患者肺组织Ｆａｓ／ＦａｓＬ系统表达及细胞凋亡的变化。结果：ＡＲＤＳ早期患者肺组织细胞凋亡率较对照组明显增加,且主要表现为肺泡上皮和肺血管内皮细胞凋亡增加;Ｆａｓ抗原、ＦａｓＬ在ＡＲＤＳ早期患者肺组织表达明显上调,并且Ｆａｓ、ＦａｓＬ表达的增加与肺组织细胞凋亡增加呈平行关系。结论：肺泡上皮和肺血管内皮细胞凋亡增加和Ｆａｓ／ＦａｓＬ系统活化可能参与临床ＡＲＤＳ早期的发病。     

特发性肺纤维化患者支气管/肺泡上皮细胞凋亡和Fas/FasL基因表达

目的：检测细胞凋亡、Fas/FasL mRNA及其蛋白在特发性肺纤维化患者肺泡/支气管上皮细胞的表达,探讨细胞凋亡和促凋亡信号在此疾病中的意义。方法：应用末端原位杂交（TUNEL）、原位杂交、免疫组化技术,对12例特发性肺纤维化患者的肺活检组织（IPF组）及10例正常肺组织（对照组）检测了细胞凋亡、Fas/FasL mRNA及其蛋白表达的变化。结果：特发性肺纤维化组肺泡/支气管上皮细胞凋亡指数上调,明显高于对照组（P〈0.01）;IPF组肺泡/支气管上皮细胞中Fas/FasL mRNA及其蛋白表达上调,高于对照组（P〈0.01）;IPF组肺泡/支气管上皮细胞凋亡指数与其Fas/FasL mRNA及蛋白表达之间均无明显相关（P〉0.05）。结论：肺纤维化时肺泡/支气管上皮细胞凋亡上调,Fas/FasL mRNA及其蛋白表达增强,在肺纤维化发生、发展中起重要作用。     

CD95 ligand (FasL)-induced apoptosis is necessary for corneal allograft survival.

Although anatomical barriers and soluble mediators have been implicated in immune privilege, it appears that the apoptotic cell death of Fas+ cells by tissue-associated CD95 ligand (Fas ligand, FasL) is an important component. One clinical example of the function of an immune privileged site is the success of human corneal transplants, where a very high percentage of transplants accept without tissue matching or immunosuppressive therapy. Since the mouse cornea expresses abundant Fas ligand and immune privilege has been implicated in the success of these transplants, we examined the role of FasL in corneal transplantation. Our results show that human corneas express functional FasL capable of killing Fas+ lymphoid cells in an in vitro culture system. Using a mouse model for corneal allograft transplantation, FasL+ orthografts were accepted at a rate of 45%, whereas FasL- grafts, or normal grafts transplanted to Fas- mice, were rejected 100% of the time. Histological analysis found that FasL+ grafts contained apoptotic mononuclear cells indicating the induction of apoptosis by the graft, while rejecting FasL- corneas contained numerous inflammatory cells without associated apoptosis. Taken together our results demonstrate that FasL expression on the cornea is a major factor in corneal allograft survival and, thus, we provide an explanation for one of the most successful tissue transplants performed in humans.     

FAS,FASL及Bcl-2在化疗药物诱导RMA细胞凋亡过程中的表达

本研究通过测定RMA细胞Fas,FasL和Bcl-2表达的变化，探讨其在细胞凋亡过程中的作用。在培养的小鼠T淋巴瘤RMA细胞系中加化疗药物地塞米松（DEX）、足叶乙甙（VP－16）、三氧化二砷（As2O3)及维甲酸（ATRA）以及培养细胞中先分别与细胞国子IL－2，IL－6或GM－CSF共同培养后再加入上述药物，观察对细胞凋亡的影响及细胞凋亡过程中Fas,FasL mRNA,Fas及Bcl-2抗原的表达。DEX和VP－16能上调Fas和FasL表达，促进细胞凋亡，Bcl-2表达无变化。ATRA可下调Bcl-2表达，但不影响Fas和FasL系统，也未观察到有细胞凋亡。As2O3可以诱导细胞凋亡,但Fas,FasL及Bcl-2表达均无变化。提示不同药物对一种细胞可能通过不同的信号途径诱导调亡，而Fas系统诱导的细胞凋亡需要Fas和FasL共同参与。单独用IL－2，IL－6或GM－CSF虽然使Fas蛋白增加，但不引起细胞凋亡；如同时并用IL－2和IL－6则Fas和FasL表达均上升，并诱导细胞凋亡。上述细胞因子与化疗药物并用时可减低药物量，促进药物的凋亡诱导作用。在无FasL表达情况下，抗Fas单克隆抗体能诱导RMA细胞凋亡。实验结果表明，细胞因子与化疗药物可协同作用诱导细胞凋亡，Fas-FasL系统参与DEX和VP－16诱导的RMA细胞凋亡过程，不同的药物可以通过不同的信号途径诱导细胞凋亡。     

缺氧缺血肺损伤新生鼠肺组织细胞凋亡及Fas／FasL mRNA的表达和意义

目的：探讨细胞凋亡与缺氧缺血肺损伤发生、发展的关系以及Fas／FasL系统表达的意义。方法：通过复制缺氧、缺氧后吸入纯氧大鼠肺损伤模型,采用TUNEL法、原位杂交检测、SqRT-PCR技术观察肺组织细胞凋亡情况、FasmRNA、FasLmRNA表达强度。结果：缺氧组或缺氧吸入纯氧组在缺氧4h后即可见大鼠肺泡上皮细胞和肺血管内皮细胞出现凋亡现象,并随着时间延长,细胞凋亡指数增高(P=0．003,P=0．005),同时FasmRNA、FasLmRNA表达上调,且缺氧后吸入纯氧组大鼠FasmRNA、FasLmRNA表达较单纯缺氧组明显增强(P<0．05)。结论：细胞凋亡与FasmRNA、FasLmRNA表达的上调可能参与缺氧和缺氧后吸入纯氧时导致的肺损伤。     

急性肺损伤大鼠肺组织细胞凋亡及Fas/FasL系统表达改变及其意义

目的：探讨细胞凋亡与急性肺损伤（ＡＬＩ）发生、发展的关系以及Ｆａｓ和／ＦａｓＬ系统表达改变的意义。方法：复制内毒素性大鼠ＡＬＩ模型;采用ＴＵＮＥＬ法、原位杂交、半定量逆转录聚合酶链反应（ＳｑＲＴ ＰＣＲ）及免疫组化等技术观察大鼠ＡＬＩ发生过程中,肺组织细胞凋亡变化以及Ｆａｓ／ＦａｓＬ系统蛋白质和ｍ ＲＮＡ表达的改变。结果：内毒素性ＡＬＩ早期（＜ ２４ 小时）,大鼠肺泡上皮细胞和肺血管内皮细胞凋亡明显增加;肺组织Ｆａｓ／ＦａｓＬｍ ＲＮＡ和蛋白质表达明显上调,且与肺组织细胞凋亡的增加相一致。结论：肺组织细胞凋亡以及Ｆａｓ／ＦａｓＬ系统表达明显上调可能参与大鼠ＡＬＩ的发病机制。     

凋亡相关基因Fas和FasL在糖尿病大鼠下颌下腺内的表达

目的：观察糖尿病大鼠下颌下腺内凋亡相关基因Fas和FasL的表达变化。方法：SD雄性大鼠随机分为4周、12周模型组及对照组。用链脲佐菌素复制出糖尿病动物模型，分别于第4、12周后测体重和血糖．并取下颌下腺组织，应用免疫组织化学方法检测Fas及FasL表达变化，计算机图像分析系统测平均光密度值（MOD）。结果：大鼠下颌下腺内有Fas及FasL表达，分布于颗粒曲管、纹状管及小叶间导管上皮细胞胞质及部分细胞核内。对照组呈Fas及FasL弱阳性，4周模型组多呈中等阳性，部分呈强阳性；12周模型组大多呈强阳性。与对照组比较，4周、12周模型组各级导管上皮细胞内Fas及FasLMOD值均增高（P〈0．01）。结论：大鼠下颌下腺内Fas及FasL表达随糖尿病病程延长而增强，可能在糖尿病时下颌下腺组织凋亡中起重要作用。[著者文摘]     

In vivo inhibition of Fas ligand-mediated killing by TR6, a Fas ligand decoy receptor.

TR6, a member of the tumor necrosis factor (TNF) receptor superfamily, has recently been shown to bind to Fas ligand (FasL) and inhibit FasL-mediated cell killing in vitro. In the current study, we demonstrate that TR6 can block the lethal activity of FasL in multiple in vitro systems, and extend this finding to an in vivo model of hepatitis. The binding of human TR6 to human FasL was verified with BIAcore chip technology. Human primary hepatocytes, HT-29 cells and Jurkat cells were assayed for viability to demonstrate TR6 inhibition of FasL-mediated cytotoxicity in vitro. Human TR6 was also shown to cross-react with membrane-bound mouse FasL, since the in vitro cytotoxic activity of L929 cells transfected with murine FasL was inhibited in the presence of human TR6. In vivo, FasL-induced acute, lethal, fulminant hepatic apoptosis resulting in death within 2 h of intravenous injection into Fas+ mice, but not Fas- MRL/lpr mice. Pretreatment of mice with TR6 blocked FasL-induced mortality, presumably by attenuating FasL-induced hepatic apoptosis. Thus, in both in vitro and in vivo systems, TR6 acts as a functional FasL decoy receptor and may be clinically useful in the treatment of hepatitis and other diseases associated with FasL-mediated tissue injury.     

A novel bystander effect involving tumor cell-derived Fas and FasL interactions following Ad.HSV-tk and Ad.mIL-12 gene therapies in experimental prostate cancer

To enhance the NK population induced by Herpes Simplex virus thymidine kinase (HSV-tk) gene transduction and ganciclovir (GCV) treatment, adenovirus-mediated (Ad) expression of IL-12 was added to Ad.HSV-tk + GCV as combination gene therapy. This approach resulted in improved local and systemic growth suppression in a metastatic model of mouse prostate cancer (RM-1). In vitro assay of tumor infiltrating lymphocytes noted superior lysis of both RM-1 and Yac-1 targets with combination therapy, but in vivo depletion of NK cells only negatively impacted on systemic growth inhibition. TUNEL assay of primary tumors noted induction of apoptosis between two and four times higher than controls lasting for 6-8 days post-vector injection. After demonstrating that Ad.HSV-tk/GCV and Ad.mIL-12-induced IFN-gamma independently up-regulated expression of FasL and Fas, respectively, studies examined tumor cell-mediated death through Fas/FasL-induced apoptosis as a mechanism of primary tumor growth suppression. In vitro, combination therapy at low vector doses resulted in synergistic growth suppression, which could be negated by the addition of anti-FasL antibody. In vivo co-inoculation of an adenovirus expressing soluble Fas resulted in combination therapy-treated tumors, which were three times larger than expected, and a reduction in apoptosis to baseline levels. In FasL knockout mice, combination therapy maintained the superior results experienced in wild-type mice, indicating that tumor cell, not host cell FasL, was responsible for Fas transactivation. Therefore, the combination of Ad.HSV-tk/GCV + Ad.mIL-12 results in enhanced local growth control via apoptosis due to tumor cell expression of Fas and FasL and improved anti-metastatic activity secondary to a strong NK response.     

Expression of Fas antigen and Fas ligand in acute liver injury induced by carbon tetrachloride in rat]

OBJECTIVE: To investigate the dynamics of expression of Fas antigen and Fas ligand (FasL) in a rat model of carbon tetrachloride-induced acute liver injury, and explore the role of apoptosis in liver injury. METHODS: Thirty-five healthy male Wistar rats were randomly divided into normal control group and experiment group, and the latter group was divided into six subgroups: 3, 9, 16, 24, 36 and 48 hours groups with 5 rats in each group. The liver injury was induced by carbon tetrachloride. Sections of liver tissue were stained with hematoxylin and eosin and observed under optical microscope. Fas antigen and FasL in rat liver were determined at different time points with immunohistochemical method. Hepatocytes apoptosis were observed with terminal deoxynucleotidyl-transferase mediated dUTP-biotin nick end labeling (TUNEL) method. Superoxide dismutase (SOD) activity and malondialdehyde (MDA) concentration in the liver tissues were analyzed at the same time point. Serum aspartate aminotransferase (ALT) and alanine aminotransferase (AST) levels were also determined. RESULTS: Fas antigen and FasL were expressed in the liver tissues of control rats. Following carbon tetrachloride challenge, severe liver injury took place in rats as revealed under microscope and a large amount of hepatocytes apoptosis was found. Hepatic Fas and FasL expression were both increased markedly from 3 to 48 hours after carbon tetrachloride challenge in experiment group. Liver MDA concentration and serum ALT and AST were elevated significantly, while SOD activity decreased remarkably in the experiment group compared with control group (P<0.05 or P<0.01). CONCLUSION: Expression of Fas/FasL is remarkably induced in acute liver injury and accords with the changes of hepatocytes apoptosis, which suggests that apoptosis mediated by Fas/FasL may play an important role in the pathogenesis of acute liver injury.     

急性肝损伤大鼠肝脏Fas和FasL的表达及其意义

目的 研究急性肝损伤大鼠肝脏Fas和FasL的表达情况，探讨细胞凋亡在中毒性肝损伤发病中的地位及其意义。方法 健康雄性Wistar大鼠35只，随机分为正常对照组和实验组，实验组再分为3、9、16、24、36和48h6个亚组，每组5只。制备四氯化碳中毒性肝损伤动物模型，采用苏木素-伊红（HE）染色，光镜下观察肝组织损伤情况，采用免疫组化方法测定不同时间点肝组织Fas和FasL的表达，采用末端脱氧核苷酸转移酶介导的dUTP缺口末端标记法（TUNEL）观察肝细胞凋亡情况。同时测定各时间点血清丙氨酸转氨酶（ALT）、天冬氨酸转氨酶（AST）和肝组织超氧化物歧化酶（SOD）活性、肝组织丙二醛（MDA）含量变化。结果 Fas和FasL在正常大鼠肝细胞中未见表达，实验组3h后即开始有明显表达，并随时间延长表达相应增强；病理学和TUNEL检测结果均显示肝脏有严重损伤，大量肝细胞发生凋亡。大鼠染毒后血清ALT、AST活性和肝组织MDA含量明显升高，肝组织SOD活性显著降低，与正常对照组比较差异均十分显著（P〈O．05或P〈O．01）。结论 大鼠急性肝损伤时Fas和FasL表达显著增加，和肝细胞凋亡变化相一致，提示Fas／Fasl。系统及介导的细胞凋亡反应在中毒性肝损伤的发病机制中可能占有重要地位。     

大肠腺癌Fas-FasL表达及其浸润淋巴细胞FasL的表达和临床病理研究

目的:探讨大肠腺癌Fas-FasL表达及其浸润淋巴细胞FasL表达的临床病理意义。方法:采用免疫组织化学方法分别检测40例大肠正常粘膜上皮、20例良性增生息肉、44例腺瘤和50例腺癌(含各分期)的Fas-FasL的表达,结合流式细胞仪检测大肠腺癌组织细胞的凋亡率。结果:免疫组织化检测40例正常粘膜上皮、20例增生性息肉、44例腺瘤、25例高分化腺癌、15例中分化腺癌、10例低分化腺癌,Fas表达逐渐下调,FasL逐渐上调。大肠腺癌组织、腺瘤与正常粘膜上皮的Fas-FasL阳性率表达均有显著性差异(P<0·05),正常粘膜上皮与增生性息肉的Fas-FasL阳性率表达无显著性差异(P>0·05),不同分化程度的大肠腺癌组织中Fas-FasL的表达均无显著性差异(P>0·05)。流式细胞仪检测50例大肠腺癌组织细胞凋亡率显示,在Fas蛋白阳性组中,浸润淋巴细胞FasL表达量与癌细胞凋亡指数呈正相关(P<0·05)。Fas蛋白阴性组中大肠腺癌凋亡指数与浸润淋巴细胞FasL表达无相关性(P>0·05)。结论:①Fas和FasL从正常粘膜上皮到腺瘤至癌变均有上调或下调的表达,推测Fas-FasL系统在大肠粘膜上皮癌变过程中可能起重要作用。②大肠腺癌细胞免疫逃避的机制之一可能是不表达或是低表达Fas。     

N-乙酰半胱氨酸对百草枯中毒大鼠肺组织细胞凋亡及Fas/FasL的影响

目的 探讨百草枯( paraquat,PQ)中毒所致大鼠急性肺损伤时N-乙酰半胱氨酸( N-acetylcysteine,NAC)对肺组织的细胞凋亡和Fa/FasL表达的影响.方法 将SD大鼠随机(随机数字法)分为对照组、PQ染毒组和NAC治疗组,每组15只.复制PQ染毒大鼠急性肺损伤模型,腹腔注入2％百草枯液( 25 mg/ kg);NAC治疗组为0.5h后对PQ染毒大鼠,再腹腔注射NAC (200 mg/kg)进行干预;对照组腹腔注射等量生理盐水.利用原位缺口末端标记(TUNEL)法检测肺组织细胞凋亡率,采用逆转录-聚合酶链反应(RT-PCR)和蛋白质印迹(Western blot)方法分别检测肺组织Fas/FasL mRNA和蛋白的表达.结果 PQ组和对照组相比细胞凋亡率和Fas/FasL系统表达差异均具有统计学意义(P＜0.05);NAC治疗组细胞凋亡率和fas/fasL表达明显降低,和PQ组相比差异均有统计学意义(P＜0.05).结论 NAC可能通过抑制Fas/FasL系统活化抑制百草枯中毒大鼠肺组织细胞凋亡.     

Functional expression of Fas and Fas ligand on human colonic intraepithelial T lymphocytes

The expression of Fas, a cell surface receptor directly responsible for triggering cell death by apoptosis, and its ligand (FasL) was investigated on both human colonic intraepithelial T lymphocytes (IELs) and peripheral blood mononuclear lymphocytes (PBMLs). FACS analysis indicated that IELs have increased expression of Fas compared with PBMLs, together with the progress activation marker, CD45RO. A discrete fraction of freshly isolated IELs also constitutively expressed FasL, perhaps as a result of recent in vivo activation. Using monoclonal antibody APO2.7, which detects mitochondrial 7A6 antigen specifically expressed by cells undergoing apoptosis, we further investigated the apoptosis-inducing effect of anti-Fas monoclonal antibody (CH11) on both IELs and PBMLs. FACS analysis revealed that CH11 increased the percentage of apoptotic cells, in IELs but not in PBMLs. Culture with anti-FasL monoclonal antibody (4H9) significantly recovered cell viability in IELs, but not in PBMLs. These results indicate that IELs constitutively express both Fas and FasL and that Fas crosslinking generates signals resulting in apoptosis, outlining a potential mechanism involved in intestinal tolerance.     

Functional expression of Fas and Fas ligand on human gut lamina propria T lymphocytes. A potential role for the acidic sphingomyelinase pathway in normal immunoregulation.

The expression and function of Fas (CD95/APO-1), a cell surface receptor directly responsible for triggering cell death by apoptosis, was investigated on human T lymphocytes resident within the intestinal lamina propria, a major site of antigen challenge and persistent lymphocyte activation. Three color immunofluorescence and FACS analysis indicated that virtually all freshly isolated human gut lamina propria T lymphocytes (T-LPL) express Fas, together with the marker of progress activation CD45R0. A discrete fraction of freshly isolated T-LPL also constitutively expressed Fas ligand (FasL), perhaps as a result of recent in vivo activation. Importantly, whereas Fas cross-linking did not result in apoptosis induction in peripheral blood T lymphocytes (T-PBL), Fas was found to be fully effective in generating the apoptotic signal in T-LPL. This was associated with the activation of an acidic sphingomyelinase and with ceramide generation, early events known to be involved in Fas-mediated apoptotic signaling. By contrast, acidic sphingomyelinase activation and ceramide production were not detectable in T-PBL after Fas cross-linking. However C2-ceramide, a cell permeant synthetic analog of ceramide, could efficiently induce apoptosis in T-LPL and T-PBL when added exogenously. These data indicate that T-LPL constitutively express both Fas and FasL and that Fas cross-linking generates signals resulting in sphingomyelin hydrolysis and apoptosis, outlining a potential mechanism involved in intestinal tolerance. Moreover, they provide the first evidence of a role for ceramide-mediated pathways in normal immunoregulation.     

Nonviral genetic transfer of Fas ligand induced significant growth suppression and apoptotic tumor cell death in prostate cancer in vivo

To accomplish efficient nonviral gene therapy against prostate cancer (PC), Epstein-Barr virus (EBV)-based plasmid vectors containing EBNA1 gene and oriP were employed and combined with a cationic polymer or cationic lipid. When EBV-plasmid/poly-amidoamine dendrimer complex was injected into PC-3-derived tumors established in severe combined immunodeficiency mice, a considerable expression of marker gene was obtained in the tumors, and the expression level was more than eight-fold higher than that achieved by conventional plasmid vector/dendrimer. Since most PC cells express the apoptotic signal molecule Fas (Apo-1/CD95) on their surface, Fas ligand (FasL) gene was transferred into PC cells to kill the tumor cells. In vitro transfection with pGEG.FasL (an EBV-plasmid with the FasL gene) significantly reduced the viability of PC cells, which subsequently underwent apoptosis. Intratumoral injections of pGEG.FasL into PC induced significant growth suppression of the xenograft tumors, in which typical characteristics of apoptosis were demonstrated by TUNEL staining and electron microscopic observations. When pGEG.FasL transfer was accompanied by systemic administrations of cisplatin, the tumors were inhibited even more remarkably, leading to prolonged survival of the animals. FasL gene transfection by means of EBV-based plasmid/cationic macromolecule complexes may provide a practical therapeutic strategy against PC.     

Differential expression of Fas (CD95) and Fas ligand on normal human phagocytes: implications for the regulation of apoptosis in neutrophils

Human neutrophils, monocytes, and eosinophils are known to undergo apoptotic cell death. The Fas/Fas ligand pathway has been implicated as an important cellular pathway mediating apoptosis in diverse cell types. We conducted studies to examine the importance of the Fas/FasL system in normal human phagocytes. Although Fas expression was detected on neutrophils, monocytes, and eosinophils, constitutive expression of FasL was restricted to neutrophils. The three types of phagocytes demonstrated differential sensitivity to Fas-induced apoptosis. Only neutrophils were highly susceptible to rapid apoptosis in vitro after stimulation with activating anti-Fas IgM (mAb CH-11). Fas-mediated neutrophil apoptosis was suppressed by incubation with G-CSF, GM-CSF, IFN-gamma, TNF-alpha, or dexamethasone, as well as the selective tyrosine kinase inhibitors, herbimycin A and genistein. Spontaneous neutrophil death in vitro was partially suppressed by Fas-Ig fusion protein or antagonistic anti-Fas IgG1 (mAb ZB4). In coculture experiments, neutrophils released a soluble factor inducing death in Fas-susceptible Jurkat cells via a mechanism sensitive to the presence of Fas-Ig or anti-Fas IgG1. Immunoblot analysis using specific anti- human FasL IgG1 (mAb No. 33) identified a 37-kD protein in lysates of freshly isolated neutrophils and a 30-kD protein in the culture supernatant of neutrophils maintained in vitro. Our results suggest that mature neutrophils may be irrevocably committed to autocrine death by virtue of their constitutive coexpression of cell-surface Fas and FasL via a mechanism that is sensitive to proinflammatory cytokines, glucocorticoids, and inhibitors of tyrosine kinase activity. Furthermore, neutrophils can serve as a source of soluble FasL, which may function in a paracrine pathway to mediate cell death.