CTLA4-FasL双功能融合蛋白分子抑制混合淋巴细胞反应及促进淋巴细胞凋亡

目的 构建人CTLA4-FasL融合蛋白真核表达载体，表达CTLA4-FasL融合蛋白，通过体外实验初步研究其生物学特性。方法 通过特异引物分别扩增出CLTA4和FasL胞外区的cDNA，将它们拼接后，克隆入真核表达载体pcDNA3．1( )中，体外表达纯化。Western blot分析CTLA4-FasL融合蛋白的抗原性。体外细胞结合试验研究其结合特异性配体作用。混合淋巴细胞反应研究其抑制免疫应答的效应。结果 测序证实所扩增的PCR产物分别是CLTA4和FasL胞外区的cDNA，其序列与文献报道相符。成功构建了pcDNA3．1-CTLA4-FasL真核表达载体。Western blot分析结果显示，表达获得的蛋白具有CTLA4和FasL的抗原性。体外细胞结合试验显示，CTLA4-FasL融合蛋白可以分别与Jurkat细胞表面的Fas受体和Raji细胞表面的町分子结合。混合淋巴细胞反应结果显示，该融合蛋白可以有效抑制异基因淋巴细胞的刺激作用及诱导淋巴细胞凋亡，并显示了显著的协同效应。结论 成功构建了CTLA4-FasL融合蛋白真核表达载体，体外表达并纯化了CTLA4-FasL融合蛋白，体外实验证实CTLA4-FasL融合蛋白是一个可以有效抑制免疫应答的双功能分子。     

CTLA4.FasL双功能融合基因真核表达载体的构建与表达

目的:构建携带CTLA4.FasL双功能融合基因的真核表达质粒,并在HEK293细胞中表达。方法:PCR扩增得到CTLA4和FasL胞外区编码序列,后用重叠PCR的方法将该两段序列融合,且在两者间插入接头序列(编码一柔性短肽GGSGG),所得的基因片段命名为CTLA4.FasL。XhoⅠ/KpnⅠ双酶切后,定向克隆至质粒pcDNA3.1(-),构建成真核表达载体pcDNA3.1(-)-CTLA4.FasL。转染入HEK293细胞,RT-PCR和Western blot验证融合基因的表达。结果:重叠PCR扩增获得CTLA4.FasL融合基因。真核表达载体pcD-NA3.1(-)-CTLA4.FasL成功构建,并在HEK293细胞表达。结论:成功构建了携带双功能融合基因的真核表达载体,为利用CTLA4.FasL基因修饰肝干细胞用于同种细胞移植治疗奠定了基础。     

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。     

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。     

可溶性人TRAIL分子对Jurkat细胞的杀伤作用

目的　研究可溶性人TRAIL蛋白 (sTRAIL)对Jurkat细胞的生长抑制效应及凋亡诱导作用。方法　通过RT PCR扩增人TRAIL分子胞外区 4 1～ 2 81的密码子 ,利用大肠杆菌DH5α表达该可溶性片段 ,经纯化和复性后 ,诱导Jurkat细胞 ,通过显微镜、台盼蓝排斥试验、MTT法、流式细胞仪和DNA断裂实验检测细胞增殖和细胞凋亡。结果　sTRAIL蛋白纯度达 90 %以上。用 0 .5～ 10 .0 μg/ml的蛋白诱导Jurkat细胞 12h以上细胞的生长和增殖即被显著抑制 ,并且观察到凋亡峰及DNA的片段化等凋亡的特征性变化 ,细胞的生长抑制率与凋亡率也呈剂量依赖和时间依赖关系。结论　利用大肠杆菌制备的sTRAIL41 2 81蛋白对Jurkat细胞具有明显的增殖抑制效应和凋亡诱导作用。     

ICA、PJA逆转人高转移肺癌细胞Fas/FasL途径免疫逃逸机制的研究

目的：研究ICA、PJA对人高转移肺癌细胞PG细胞免疫逃逸的逆转作用。方法：MTT法检测ICA、PJh对PG细胞增殖的影响以及对CD3AK杀伤敏感性的影响。流式细胞仪检测细胞表面分子Fas、FasL表达水平和细胞凋亡。应用PG细胞与Jurkat T细胞其培养的方法体外研究FasL诱导T淋巴细胞凋亡的作用。结果：PG细胞高表达FasL，低表达Fas，对CD3AK细胞杀伤敏感性较低，并在与Jurkat T细胞共培养中诱导高表达Fas的Jurkat T细胞凋亡。：ICA、PJA对PG细胞有明显的增殖抑制作用。ICA可明显提高PG细胞Fas的表达率。ICA、PJA可明显降低PG细胞FasL的表达率。ICA、PJA可使PG细胞与Jurkat T细胞共培养中，降低Jurkat T细胞的凋亡率。ICA、PJA可提高CD3AK细胞对PG细胞的杀伤活性。结论：ICA、PJA可逆转人高转移肺癌细胞PG通过Fas／FasL途径逃避机体免疫活性细胞的攻击。     

人4-1BBL胞外区/抗CD20融合蛋白的构建和表达

目的:构建和表达人4-1BBL胞外区/抗CD20双功能融合蛋白,并测定该融合蛋白的生物学活性.方法:采用PCR和ovelap PCR方法构建人4-1BBL胞外区/抗CD20双功能融合蛋白,并用双脱氧终止法测定DNA序列;采用亲和层析法纯化该产物,并用150 g/L SDS-PAGE和Western blot鉴定纯化产物;采用FACS法鉴定纯化产物与靶细胞的结合活性.结果:DNA序列测定结果表明:人4-1BBL胞外区/抗CD20双功能融合蛋白已构建成功,表达可溶性产物的产量达4 mg/L以上,具有与Raji细胞(CD20 )和A549(4-1BB )细胞结合的活性.结论:利用融合蛋白形式,首次成功地构建了人4-1BBL胞外区/抗CD20融合蛋白,并获得较高表达.表达产物具有与相应2个靶抗原结合的活性.     

CTLA4-EGFP融合蛋白在K562细胞中的表达及其亚细胞定位研究

目的 :构建增强型绿色荧光蛋白 (EGFP)与CTLA4融合蛋白真核表达载体 ,分析其在K562细胞中的表达和亚细胞定位。方法 :以RT PCR方法克隆人CTLA4基因 ,构建CTLA4 EGFP融合蛋白的表达载体。以其转染K562细胞后 ,以流式细胞仪和激光共聚焦显微镜分析融合蛋白的表达及其亚细胞定位。结果 :从人外周血细胞中克隆到CTLA4基因的cDNA。通过PCR方法在起始位点前加入Kozak序列并删除终止密码 ,成功地构建CTLA4 EGFP融合蛋白表达载体。以该质粒转染K562细胞 2 4h后 ,CTLA4和EGFP双阳性细胞的百分率为 16%。表达的融合蛋白主要分布于胞内 ,细胞膜上分布较少。相反 ,转染空载体的细胞仅表达EGFP ,且其在细胞内呈弥散样分布。以佛波醇酯加离子霉素刺激后 ,CTLA4 EGFP融合蛋白在细胞表面表达水平升高到 2 9% ,且分布于胞内的融合蛋白向细胞膜靠近并与质膜融合 ;而转染空载体的细胞内EGFP的分布无明显改变。结论 :成功地构建CTLA4 EGFP融合蛋白表达载体 ,并在K562细胞中得到表达。表达的融合蛋白与天然CTLA4在活化T细胞中的定位和转运特点相似     

血管活性肠肽(VIP)对大鼠Leydig细胞FasL表达及介导Jurkat细胞凋亡的影响

目的研究VIP对大鼠Leydig细胞FasL表达及介导Jurkat细胞凋亡的影响。方法VIP作用于UU感染的SD大鼠及大鼠Leydig细胞,观察VIP对大鼠Leydig细胞FasL表达的调节,从体外及动物整体水平来探讨VIP对大鼠Leydig细胞FasL表达及介导Jurkat细胞凋亡的影响。结果在睾丸局部感染时,VIP能调节Leydig细胞FasL表达格局并能调节Leydig细胞介导Jurkat细胞的凋亡率。结论VIP参与调节大鼠睾丸局部的免疫豁免。     

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。     

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。     

CTLA-4-Fas ligand functions as a trans signal converter protein in bridging antigen-presenting cells and T cells

Co-stimulator blockade and trans inhibitory signaling, using agents such as CTLA-4-Ig and Fas ligand (FasL) respectively have been invoked as alternative strategies for suppressing pathogenic T cells. This study describes a novel hetero-bifunctional fusion protein, CTLA-4-FasL, designed to combine within a single protein both co-stimulator blocking and trans inhibitory signaling potentials. A chimeric expression cassette, in which the ectodomain coding sequences for CTLA-4 and FasL were linked in-frame, was used to produce a CTLA-4-FasL fusion protein. CTLA-4-FasL binding to both B7-1/B7-2-expressing Daudi B cells and Fas-expressing Jurkat T cells was documented by immunofluorescence and flow cytometry. The capacity of CTLA-4-FasL to induce apoptosis in Jurkat targets was markedly enhanced by the addition of Daudi and other B7-1/B7-2(+) B cell lines, which provided a membrane platform for the otherwise soluble CTLA-4-fusion protein. Moreover, in dual-chamber experiments, Daudi cells pre-coated with CTLA-4-FasL demonstrated Jurkat inhibitory activity that was cell-contact dependent. Significantly, when used to inhibit in vitro cellular proliferation of peripheral blood mononuclear cells, CTLA-4-FasL was approximately 1000-fold more potent than the extensively characterized CTLA-4-Ig fusion protein. Furthermore, the degree of inhibition induced by CTLA-4-FasL substantially surpassed that observed for CTLA-4-Ig and a soluble FasL when used in combination. CTLA-4-FasL represents the first of a novel class of fusion proteins, designated here as 'trans signal converter proteins', that combine trans signal masking and direct trans signaling functions.     

Apoptosis provoked by the oxidative stress inducer menadione (Vitamin K(3)) is mediated by the Fas/Fas ligand system.

Menadione, or vitamin K(3) (VK(3)), a potent oxidative stress inducer, has been recently used as an effective and remarkably safe cytotoxic drug for treatment of several human tumors. VK(3) induces apoptotic cell death through a poorly understood mechanism. Here we show for the first time that VK(3)-induced apoptosis requires the Fas/FasL system. Spleen cells from both Fas- and FasL-deficient mice (C57BL/6-lpr and C57BL/6-gld, respectively) had much lower levels of VK(3) apoptosis in vitro compared to cells from control C57BL/6 mice. VK(3) cytotoxicity toward mouse splenocytes was also blocked with a Fas-Fc fusion protein. VK(3) induced apoptosis in Jurkat cells, coincident with an increase in both Fas and FasL expression. A FasL-resistant variant of these Jurkat cells was also resistant to VK(3)-induced apoptosis. Furthermore, because VK(3) effects were inhibited by glutathione, a potent antioxidant, oxidative stress was linked to the Fas/FasL system. Moreover, since the Jurkat cell lines were p53 null, the activation of Fas/FasL system after oxidative stress apparently acted through a p53-independent pathway. The therapeutic relevance of the K vitamins has been growing in recent years; our findings offer new insight for improving and expanding their applications.     

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     

CD40.FasL inhibits human T cells: evidence for an auto-inhibitory loop-back mechanism

A chimeric CD40.FasL (CD40-CD95L) protein was designed with the combined capacities to bind to two surface receptors on activated T cells, CD40 ligand (CD40L; CD154) and Fas receptor (CD95). CD40.FasL, once tethered to the cell surface via one of its ends, can transmit a signal via its other end. In principle, simultaneous triggering from both ends is possible, and thus there is the intriguing potential for 'auto-inhibition' if such dual triggering occurs on the same cell itself. Several lines of evidence support this mechanism: (i) CD40.FasL is cytotoxic to Fas receptor-positive cell lines of different cell lineages, (ii) CD40.FasL's function is potentiated when there is enforced expression of CD40L on target cells, (iii) CD40.FasL inhibition does not require intercellular contact, as demonstrated by soft agar clone formation and cell dilution analysis and (iv) introduction of exogenous CD40 into the system interferes with CD40.FasL inhibition. Taken together, these data are consistent with a 'loop-back' inhibitory mechanism within individual activated (CD40L and Fas receptor expressing) T cells causing suicide of these T cells. Significantly, this type of fusion protein provides a unique way to confine immunoinhibition to activated T cells.     

Synergistic action of protein kinase C theta and calcineurin is sufficient for Fas ligand expression and induction of a crmA-sensitive apoptosis pathway in Jurkat T cells

Deletion of activated peripheral T cell clones by apoptosis requires the regulated expression of Fas ligand (FasL) and sensitization of these cells to CD95-mediated signaling. To investigate the signaling pathways responsible for FasL expression in T cells, we tested-besides subfamily-selective protein kinase C (PKC) inhibitors - the effect of constitutively active mutants of representatives of all PKC subfamilies, i.e. PKCalpha,epsilon,theta,iota, on FasL luciferase promoter reporter constructs. In synergy with a constitutively active form of protein phosphatase 2B calcineurin (CaN), only PKCtheta, but not PKCalpha,epsilon,iota, preferentially induced FasL promoter reporter activity and, consequently, FasL protein expression in Jurkat T cells. Activation of an inducible PKCtheta AE-estrogen receptor fusion mutant led to a CaN-dependent and rapid FasL reporter activity detected as early as 4 h after addition of 4-hydroxytamoxifen, incidating a direct effect of PKCtheta action on FasL expression. Consistently, in Jurkat T cells, expression of PKCtheta AE / CaN significantly enhanced FasL protein expression and apoptosis in a CD95-dependent manner since cell death was not observed in T cells co-expressing the caspase-8 inhibitor crmA. Taken together, our results support the notion that PKCtheta and CaN are sufficient to regulate apoptosis through FasL expression.     

脱氢表雄酮诱导CD4~+T细胞系Jurkat细胞凋亡的初步探索

为研究脱氢表雄酮(DHEA)对Jurkat细胞增殖活性和凋亡的影响,用不同浓度的DHEA处理Jurkat细胞12 h、24 h后,用MTT法测定细胞活性;Hoechst染色观测细胞形态的改变;碘化丙啶(PI)染色检测细胞凋亡;Annexin V/PI双染法检测细胞膜变化;DNA阶梯状电泳分析细胞DNA断裂;荧光显微镜分析细胞线粒体膜电位变化;并用RT-PCR和流式检测凋亡时细胞中Fas和FasL的mRNA和蛋白表达的情况。结果显示,DHEA在10~(-7)mol/L时对Jurkat细胞有显著的增殖抑制作用(P<0.05)和诱导凋亡效果,细胞凋亡率比对照组分别升高2.48%和2.52%;Annexin V/PI双染法检测,处理组凋亡细胞比率比对照组也明显增加;且随着DHEA剂量的增加细胞线粒体膜电位倒塌明显增强,Fas和FasL的mRNA和蛋白水平也随之增加。以上结果表明,DHEA在高浓度时对Jurkat细胞有一定的抑制增殖并诱导其凋亡的作用,Fas/FasL通路和膜电位的改变在此机制中发挥了相应的作用。