腺病毒介导入B7—1基因对肝癌细胞免疫原性的影响

目的 研究同时含人ｐ５３、ＧＭ－ＣＳＦ、Ｂ７－１、ＩＬ－２基因的重组腺病毒载体Ａｄ－ｍｕｌｔｉｇｅｎｅｓ,对肝癌细胞免疫原性的影响。方法 应用人外周血淋巴细胞和肿瘤细胞的混合培养、外周血Ｔ淋巴细胞杀伤活性试验,分析导入目的基因的人肝癌细胞免疫原性的变化。结果 导入Ａｄ－ｍｕｌｔｉｇｅｎｅｓ的肝癌细胞系ＨｅｐＧ２、ＢＥＬ－７４０２,体外能刺激正常人外周血Ｔ淋巴细胞的增殖,并能增强Ｔ淋巴细胞的杀瘤细胞活性,加入ＩＬ－１２有协同增强作用。结论 肝癌细胞导入含Ｂ７－１基因的Ａｄ－ｍｕｌｔｉｇｅｎｅｓ后,其免疫原性得到增强。     

共刺激分子B7-1与IL-6协同诱导T细胞活化的研究

目的：探讨Ｂ７－１单独或者与ＩＬ－６联合体外诱导Ｔ细胞活化的能力。方法：在混合淋巴细胞肿瘤细胞培养（ＭＬＴＣＳ）后,测定淋巴细胞增殖指数和ＣＴＬ杀伤活性。结果：Ｂ７－１＾＋的Ｂ１６细胞能够较有效地刺激淋巴细胞增殖,诱导特导ＣＴＬ杀伤活性,当与ＩＬ－６结合时效更加显著。结论：Ｂ７－１基因在肿瘤细胞中表达可增强其免疫原性在体外有效诱导Ｔ细胞活化;在此过程中ＩＬ－６与Ｂ７－１分子存在协同效应。     

鼠抗人B7-1分子功能性单克隆抗体的制备及生物学特性

目的：制备鼠抗人Ｂ７－１分子的功能性单克隆抗体,研究其对高表达相应配基分子细胞的生物学效应。方法：用两株转入Ｂ７－１基因细胞株ＸＧ７－Ｂ７和Ｌ－Ｂ７分别作为免疫原及检测细胞株,利用Ｂ淋巴细胞杂交瘤技术制备单克隆抗体。以快速定性试纸分析法鉴定单抗所属的小鼠ＩｇＧ亚类,采用竞争抑制及间接免疫荧光法分析单抗的特异性和亲和力。以高表达Ｂ７－１分子的恶性淋巴瘤细胞Ｒａｊｉ和Ｄａｕｄｉ为靶细胞,分析单抗对其生     

B7—1基因修饰的肿瘤细胞疫苗抗肿瘤的实验研究

目的：研究B7-1基因修饰的肿瘤细胞作为瘤苗的抗肿瘤作用。方法：通过逆转录病毒载体。将小鼠B7-1基因导入EL-4淋巴瘤细胞中,研究EL-4/B7-1在同系C57BL/6小鼠中的成瘤性及其诱导抗肿瘤免疫的效果。结果：转B7-1基因诱导了CD80的高表达,EL-4/B7-1细胞在小鼠中的成瘤性下降,在肿瘤生长的早期对实验性荷瘤小鼠进行治疗。基因修饰的瘤苗作用明显增强,EL-4/B7-1细胞能有效地保护野生型肿瘤细胞的攻击,射线灭活的EL-4/B7-1瘤苗作用减弱。结论：B7-1基因修饰的肿瘤疫苗可诱导体内的抗肿瘤免疫反应,导致肿瘤的部分根除,为基因修饰的肿瘤疫苗的临床应用提供了实验依据。     

多发性硬化患者B淋巴细胞B7-1、B7-2的表达及临床意义

多发性硬化 (Ｍｕｌｔｉｐｌｅｓｃｌｅｒｏｓｉｓ,ＭＳ)病因及发病机制至今未明 ,我们选择抗原提呈细胞Ｂ淋巴细胞 ,观察其Ｂ7分子表达 ,探讨ＭＳ患者免疫学发病机制。研究对象为 45例ＭＳ患者 ,男性 2 3例 ,女性 2 2例 ,年龄 2 0～ 42岁 ,平均 32 .5± 9.1岁 ,病程 2月～ 11年 ,平均病程2 .18年 ,标准 :依据Ｐｏｓｅｒ诊断标准为临床确诊的ＭＳ患者 ,其中活动期 (ａｃｔｉｖｅＭＳ ,ＡＭＳ) 2 5例 ,稳定期 (ｓｔａｂｌｅＭＳ ,ＳＭＳ)2 0例。所有患者在测定Ｂ淋巴细胞表面Ｂ7分子前 2月内未用免疫抑制剂或激素。对照组为 2 0例健康献血员…     

重组B7—2腺病毒载体的构建及其诱导小鼠抗肝癌免疫的初步研究

探讨重组腺病毒介导的Ｂ７－２基因转染对小鼠肝癌细胞免疫原性的影响。构建Ｂ７－２的重组腺病毒载体，通过重组腺病毒介导，将Ｂ７－２和ｌａｃＺ基因分别转染小鼠肝癌细胞Ｈｅｐａｌ－６，并在不同时相检测Ｂ７－２和ｌａｃＺ基因的表达水平，建立小鼠肝癌肿瘤模型，在小鼠体内观察Ｂ７－２基因转染对小鼠肝癌免疫原性的影响。成功地构建了Ｂ７－２的重组腺病毒载体，用Ｂ７－２及ｌａｃＺ重组腺病毒分别转染小鼠肝癌细胞，转染后     

表达人B7-1的重组腺病毒的制备及初步鉴定

目的构建表达B7-1基因的重组腺病毒载体,制备相应的复制缺陷型重组腺病毒并检测其在喉癌细胞中的表达。方法构建携带人B7-1基因的重组穿梭载体pAdtrack-B7-1,PmeI线性化后与腺病毒载体pAdEasy-1共转化大肠杆菌BJ5183,通过同源重组得到重组腺病毒载体pAd-B7-1。将重组腺病毒载体转染HEK293包装细胞制备重组腺病毒,应用病毒悬液感染人喉癌细胞株,RT-PCR检测感染细胞中B7-1基因mRNA表达。结果酶切鉴定证实阳性pAdTrackB7-1重组穿梭载体含有目的基因B7-1,同源重组后制备的病毒载体DNA经酶切鉴定获得了阳性重组腺病毒载体,该载体能有效转染HEK293细胞并在细胞内成功包装,转染3d后可以观察到绿色荧光蛋白(GFP)表达并逐渐增多、增强。制备的Ad-B7在体外能有效感染Hep-2细胞,感染后可维持6d高水平的B7-1的表达,整体表达可持续两周。结论成功构建了同时表达B7-1的重组腺病毒载体并制备出重组腺病毒颗粒,该病毒能有效地感染喉癌细胞并表达高水平的B7-1基因,为进一步研究B7-1的功能及应用B7-1进行基因治疗奠定基础。     

小鼠B7-1基因转染的黑色素瘤细胞免疫原性探讨

目的 探讨Ｂ７－１分子对肿瘤细胞免疫原性的影响。方法 将小鼠Ｂ７－１基因转染的黑色素瘤细胞（Ｂ１６－ｍＢ７．１）与野 生型及空载体转染细胞（Ｂ１６－ｗｔ和Ｂ１６－ｎｅｏ）的免疫原性在体内外进行了比较。同源淋巴细胞肿瘤细胞混合培养（ＭＴＬＣＳ）后测定淋巴增殖指数和ＣＴＬＳ活性,将Ｂ１６－ｎｅｏｐ和Ｂ１６－ｍＢ７．１细胞接种于小鼠皮下,观察肿瘤生长速度。结果 Ｂ１６ｍＢ７．１在体外刺激淋巴细胞增殖和诱     

B7家族的新成员—B7-H1、B7-H2、B7-H3、B7-DC

T细胞的活化需要TCR与抗原肽-MHC的第一信号，以及共刺激因子的第二信号系统。B7家族是重要的共刺激分子，属于免疫球蛋白家族。除B7-1和B7-2外，近几年又发现了B7家族的新成员——B7-H1、B7-H2、B7-H3、B7-DC等，与T、B细胞的活化及免疫应答等有关。深入研究B7家族成员的结构和作用机制，有助于T、B细胞活化机制以及免疫耐受、肿瘤免疫研究的深入和发展。     

一个新的MAGE—1表位为肝癌细胞表面HLA—B7分子递呈

目的：肿瘤抗原的存在是机体识别肿瘤并激活免疫系统的物质基础。机体抗肿瘤免疫以细胞免疫为主,故寻找被T细胞识别的肝癌细胞抗原肽,为肝癌免疫治疗奠定基础。方法：对于肝癌细胞系HHCC（HLA-A2,A29,B7,B51）,应用细胞膜酸洗技术使抗原肽从细胞膜表面脱落,经过凝胶层析,反相高效液相色谱层板得到不同组份多肽,高效液相色谱=质谱仪联用技术获得抗原肽的一级结构。通过氨基酸锚定位点分析,预测其HLA配体类型;互联网上氨基酸同源性分析确定其同源性用技术获得抗原肽的一级结构,通过氨基酸锚定位点分析,预测其HLA配体类型,互联网上氨基酸同源性分析确定其同源性序列;人工合成抗原肽,HLA同型树突状细胞递呈合成抗原肽刺激特异性CTL反应,^51Cr杀伤实验检测CTL对肿瘤细胞系的杀伤作用。结果：经过反相高效液相色谱层析后可以获得10多个组份,其中一个组份经过液质联用鉴定和氨基酸同源性分别确定其序列为EPVTKAEML,是黑色素瘤抗原-1,MAGE-1（121-129）表位。由HLA-B7分子递呈,体外诱导实验表明其可以诱导出较强的CTL反应。结论：液质联用技术是寻找抗原肽的有效方法,MAGE-1抗原肽EPVTKAEML地于HLA-B7阳性及阳性的肝癌患者具有潜在的免疫治疗作用。     

Human B7-1 is more efficient than B7-2 in providing co-stimulation for alloantigen-specific T cells

Besides a signal via the T cell receptor/CD3 complex, an additional co-stimulatory signal is required for optimal T cell activation. This signal can be delivered by interaction of either B7-1 or B7-2 expressed by antigen-presenting cells with CD28 on the T cells. Comparison of the function of B7-1 and B7-2 in different experimental animal systems generated conflicting data on the roles for the co-stimulatory molecules. We therefore investigated whether there are differences between B7-1 and B7-2-mediated co-stimulation in an alloantigen-specific primary T cell response induced by B7-transfected human cell lines of epithelial origin. Both transfected keratinocyte cell lines efficiently induce T cell proliferation and the ratios of stimulator versus responder cells are similar. The kinetics of proliferation and interleukin (IL)-2, IL-4 and interferon-γ production are also comparable between both transfectant lines. However, despite equal B7 expression levels, it is consistently found that the magnitude of the B7-1-induced T cell proliferation was higher than that of B7-2. Comparison of precursor frequencies of helper T lymphocytes responsive with either B7-1 or B7-2 revealed that the frequency of B7-1-responsive T cells was higher than that of B7-2, and that the frequency of cells activated by a combination of B7-1 and B7-2 did not differ significantly from that of B7-1 alone. We therefore conclude that the B7-2-responsive T cells are part of the B7-1-responsive population, and that B7-1 on keratinocytes is more efficient in providing co-stimulation for alloantigen-specific T cells.     

Expression and function of B7-1 (CD80) and B7-2 (CD86) on human epidermal Langerhans cells

In addition to T cell receptor triggering, activation of T cells requires co-stimulatory signals that have been shown to be mainly initiated through CD28. We analyzed the expression and function of the two ligands for CD28, B7-1 (CD80) and B7-2 (CD86), on human Langerhans cells (LC), the antigen-presenting cells from epidermis. Human LC freshly isolated from epidermis (fLC) expressed significant level of B7-2, which was increased upon a short culture in vitro. In contrast, B7-1 was undetectable on fLC but appeared at the cell surface after a 3-day culture in vitro. Pre-incubation of 18-h cultured LC with anti-B7-2 monoclonal antibodies (mAb) was sufficient to abrogate the binding of CTLA4-Ig fusion protein, while a combination of both mAb against B7-1 and B7-2 was necessary to obtain a complete inhibition of CTLA4-Ig binding on 3-day cultured LC, showing the absence of a third CTLA4 ligand. The function of B7-1 and B7-2 on human LC has been analyzed by adding mAb at the beginning of mixed epidermal cell lymphocyte reactions. Anti-B7-2 mAb and CTLA4-Ig, but not anti-B7-1 mAb, strongly inhibited allogeneic, as well as recall antigen-induced T cell proliferation supported by fLC or 3-day cultured LC. Collectively, these results demonstrate that B7-2 is the major ligand for CD28/CTLA4 at the LC surface and that it plays a crucial role in human LC co-stimulatory function with little, if any, dependence on B7-1 expression.     

Expression and function of B7-1 and B7-2 in hapten-induced contact sensitivity

We analyzed the expression and function of the co-stimulatory molecules B7-1 (CD80) and B7-2 (CD86) during contact sensitivity reactions induced by the hapten 2,4-dinitrofluorobenzene (DNFB). In the normal skin, only a few epidermal Langerhans cells or dermal dendritic cells express B7-2. In contrast, following challenge with DNFB, expression of B7-2 is up-regulated in both epidermis and dermis. Importantly, B7-1 is induced later and at lower levels compared to B7-2. Intravenous injections of anti-B7-2 mAb, but not anti-B7-1 mAb partially inhibit the hapten-induced contact sensitivity reaction. Experiments in which mice are injected differentially with anti-B7-2 mAb, either before the afferent or before the efferent phase of the contact sensitivity response, suggest that B7-2 is important for successful antigen priming.     

Potential role of B7-1 and CD28 molecules in immunosuppression in leprosy

In order to understand the mechanism of unresponsiveness towards Mycobacterium leprae antigens in leprosy, we evaluated the role of M. leprae sonicate antigens in regulating the expression of the costimulatory molecules B7-1, CD28, intercellular adhesion molecule-1 (ICAM-1), LFA-1α, LFA-1β and Mac-1 on the lymphocytes of both leprosy patients and healthy subjects. It was observed that the expression of B7-1 and CD28 was significantly decreased but the levels of ICAM-1 and LFA-1α were increased in patients with untreated borderline leprosy (BL)/lepromatous leprosy (LL) disease. No remarkable change was noticed in the case of borderline tuberculoid (BT) leprosy or treated BL/LL patients. Further, a striking finding was that lymphocytes from healthy subjects cultured with a particularly high dose of M. leprae sonicate antigens down-regulated the expression of B7-1 and CD28 molecules, but up-regulated the display of ICAM-1 and LFA-1α. Furthermore, proliferation induced by M. leprae sonicate was inhibited only by anti-B7-1 antibody. Mycobacterium leprae antigen-induced suppression of the proliferation of lymphocytes of healthy volunteers and LL patients was reversed by culturing the lymphocytes with purified protein derivative (PPD). It may be concluded from the findings in this study that down regulation of B7-1 and CD28 in BL/LL leprosy patients may be responsible for a defective T cell signalling by the B7-1/CD28 pathway caused by M. leprae antigens. This may lead to clonal inactivation of M. leprae-reactive T cells, consequently the bacilli grow without restriction in macrophages.     

Both CD28 ligands CD80 (B7-1) and CD86 (B7-2) activate phosphatidylinositol 3-kinase, and wortmannin reveals heterogeneity in the regulation of T cell IL-2 secretion

In this report, the co-stimulatory signals provided by CD80(B7-1) or CD86 (B7-2) were compared to CD28 ligation by mAb.We demonstrate that while both anti-CD3 and anti-CD28 antibodiesinduced activation of phospholnositide (PI) 3-kinase, the kineticsof activation differed. Anti-CD28 produced a sustained activationof PI 3-kinase while anti-CD3 induced activation was transient.Both B7-1 and B7-2 could induce prolonged activation of PI 3-kinase.The co-stimulatory effects of B7-1 and B7-2 were dependent onCD28 cross-linking, based on complete inhibition of PI 3-kinaseactivation by CD28 antibody Fab fragments. While Jurkat T cellsco-stimulated with anti-CD3 and B7-1 or B7-2 secreted high levelsof IL-2, there were distinct effects of anti-CD28 mAb and B7-1or B7-2 on IL-2 secretion in conjunction with protein kinaseC activation. To assess functional effects of CD28 ligation,pharmacologic inhibitors of PI 3-kinase were evaluated. In Jurkatcells, efficient inhibition of PI 3-kinase activation afterB7-2 stimulation was achieved using wortmannin; however, weobserved a surprising increase in IL-2 secretion after B7 oranti-CD28 stimulation. The effect of wortmannin was concentrationdependent. Moreover, the effect was specific for receptor-mediatedactivation as wortmannin did not enhance phorbol ester pluslonomycin-induced IL-2 secretion. Another inhibitor of PI 3-kinase,LY294002, also resulted in augmentation of anti-CD28-inducedIL-2 secretion by Jurkat cells. The effects of wortmannin onIL-2 secretion were also examined in primary T cells. In markedcontrast, wortmannin resulted in a potent inhibition of anti-CD3plus B7-1 or anti-CD28-induced IL-2 secretion while phorbolester plus lonomycin-induced IL-2 secretion was wortmannin resistant.Together these observations demonstrate that signal transductionby both B7-1 and B7-2 involves PI 3-kinase, and that PI 3-kinaseor other wortmannin-sensitive targets are important for IL-2secretion. Finally, treatment of Jurkat cells with PI 3-kinaseinhibitors alone was sufficient to induce low levels of IL-2secretion. This is consistent with the notion that a wortmannin-sensitivetarget such as PI 3-kinase may down-regulate IL-2 secretionin Jurkat cells.     

Heterogeneous effects of B7-1 and B7-2 in the induction of both protective and therapeutic anti-tumor immunity against different mouse tumors

Experimental mouse tumors are classified as intrinsically immunogenic when, after a single injection into syngeneic mice as nonreplicating cell vaccines, they elicit a protective immune response against a subsequent lethal challenge. Tumors that do not retain this residual immunogenicity are defined as poorly immunogenic or nonimmunogenic. The expression of the B7-1 co-stimulatory molecule on immunogenic tumors can further increase their capacity to induce a T cell-dependent anti-tumor immunity, whereas it has limited effects on nonimmunogenic tumors. Recently, B7-2, a second molecule with an apparently similar co-stimulatory activity, has been cloned. In this report, we compare the efficiency of nonreplicating cells from one immunogenic and two nonimmunogenic mouse tumors transfected with B7-1 or B7-2 in the induction of protective and curative anti-tumor immunity. Immunogenic lymphoma cells expressing B7-1 or B7-2 are equally effective in both protecting against a subsequent challenge and curing established tumors. By contrast, nonimmunogenic adenocarcinoma and melanoma cells expressing B7-2 provide superior protective immunity, and only B7-2⁺ adenocarcinoma cells induce an efficient curative immunity. CD8⁺ and polymorphonuclear cells, but not CD4⁺ T cells, are critically involved in the rejection of the adenocarcinoma elicited by both B7-1⁺ and B7-2⁺ vaccines. These data indicate that B7-1 and B7-2 are not redundant co-stimulatory molecules and that, in these experimental models, B7-2 is superior to B7-1 in the induction of an efficient immunity when the immunogenicity of a tumor is a limiting factor.