EBV-LMP2A重组腺病毒体外转染树突状细胞激发特异性CTL的研究

目的：用EBV潜伏膜蛋白2A(EBV-LMP2A)重组腺病毒转染树突状细胞(DC)激发特异性细胞毒性T细胞(CTL)，分析CTL的特性。方法：用AdS-LaMP2A重组腺病毒转染EBV健康携带者及鼻咽癌患者的DC，与自体来源的外周血单个核细胞(PBMC)混合培养，激发LMP2A特异性CIL。用LDH释放法检测CIL杀伤活性；流式细胞术(FACS)检测培养细胞群体中CD3^ 、CD4^ 、CD8^ 、CD56^ 细胞的组成；生物活性法检测细胞培养上清中IFN-γ含量；RT-PCR分析CTL的FasL mRNA表达。结果：EBV健康携带者及鼻咽癌患者的PBMC，经AdS-LMP2A转染的自体DC两次刺激后，都能诱导出显著的EBV-LMP2A特异的CIL。EBV健康携带者CTL的杀伤活性，随DC刺激次数的增加而逐渐增强，诱导的CTL细胞群体以CD^4 和CD8^ 细胞组成为主，且CD4^ 细胞比例高于CD8^ 细胞，另含少量CD56^ 细胞；在不同时段所诱导的CTL上清中，均含一定量的IFN-γ并随刺激次数和诱导时间的延长呈上升趋势；RT-PCR研究表明，所诱导的CTL有FasL mRNA的表达。结论：以腺病毒载体介导EBV-LMP2A基因转染的成熟DC，在体外能激发较强的LMP2A特异的功能性CTL，可用于EBV相关NPC的免疫治疗。     

CD4+ CD25+调节性T细胞对树突状细胞的杀伤作用

目的 探讨CD4^＋CD25^＋调节性T细胞是否对树突状细胞发挥免疫调节作用及其可能的机制。方法 用MACS（magnetic cell sorting）从BALB／c小鼠静息T细胞分离纯化CD4^＋CD25^＋T细胞，体外细胞增殖实验观察其对CD4^＋CD25^＋T细胞的免疫抑制作用；GM-CSF／IL-4培养自体小鼠骨髓来源DC，FACS（fluorescence-activated cell sorting）鉴定其表面分子特性；以CD3／CD28单克隆抗体活化CD4^＋CD25^＋调节性T细胞，FACS体外杀伤实验研究其对自体DC的调节作用，并观察穿孔素抑制剂EGTA对上述作用的影响。结果 用MACS法成功分离出CD4^＋CD25^＋T细胞，纯度可达98％，特异性表达而Faxp3基因，能明显抑制CD4^＋CD25^＋T细胞的体外增殖；骨髓来源的DC表达CDllc、MHCⅡ及少量协同刺激分子CD80、CD86；FACS体外杀伤实验证实以CD3／CD28抗体体外活化的CD4^＋CD25^＋调节性T细胞对自体DC有显著杀伤作用（P〈0．05），穿孔素抑制剂EGTA能部分抑制该杀伤效应（P〈0．05）。结论 CD4^＋CD25^＋调节性T细胞可通过杀伤作用对自体DC发挥免疫调节作用，穿孔素／颗粒酶杀伤途径可能参与其中。     

CD86对CD8+T细胞分化的影响

目的：探讨CD86(B7-2)对CD8^ T细胞分化的影响。方法：用限制性内切酶Xho Ⅰ酶切质粒pCDM8得到CD86基因，并将其插入pCDNA3，用BamH Ⅰ酶切鉴定。用脂质体法介导pCDNA3-CD86真核表达载体转染人肝癌细胞株HMCT／21，600μg/ml G418筛选，稳定且高表达CD86的抗性克隆用流式细胞仪进行鉴定。从健康志愿者血中分离外周血单个核细胞(PB-MC)，使PBMC与靶细胞之比为20：1，共同培养48h后，用流式细胞仪检测CD3^ T细胞内IL-4和IFN-γ的表达率。结果：成功构建pCDNA3-CD86真核表达载体；CD86在HMC7721-CD86细胞中的表达率为30．8％，而在HMC7721细胞中的表达率为0．98％；健康志愿者CD3^ T细胞内IL-4和IFN-γ的表达率分别为1．92％和24．4％；PBMC与靶细胞共同培养48h后，无论是否用IFN-α刺激，IL-4，IFN-γ的阳性比值在HMC7721-CD86转染组均大于1，而在HMC7721未转染组均小于1。结论：在细胞培养中，CD86可诱导CD8^ T细胞活化，并向Tc2表型转化。     

树突状细胞负载肝癌可溶性抗原后的免疫应答

目的 用负载肝癌可溶性抗原的DC诱导肝癌特异性T细胞。方法 在体外用GM－CSF和IL－4诱导健康人外周血单核细胞，使其分化为高纯度树突状细胞（DC）。用负载人肝癌细胞株SMMC－7721可溶性抗原的DC诱导自身淋巴细胞。结果 诱导后淋巴细胞增殖指数大于1．5，表面CD56分子表达下降，CD3^ T/CD4^ T和CD3^ T/CD8^ T细胞比例增加，以CD3^ T/CD4^ T细胞比例增加最为明显。CD4／CD8比例由诱导前的0．84增加为1．04，活化前后γδ比例没有改变。活化后的淋巴细胞不但可杀伤SMMC－7721细胞，同时还可不同程度的杀伤其它3株肝癌细胞。另外，诱导7d的DC可不同程度的抑制4株肝癌细胞和胃癌细胞。结论 实验结果为肝癌DC疫苗的研究提供了理论基础。     

树突状细胞与永生化EBV转化B淋巴细胞对抗原提呈作用的比较分析

树突状细胞是抗原提呈功能最强的专职性抗原提呈细胞 ,其显著特征是刺激初始性淋巴细胞增殖 ,而EBV转化B淋巴母细胞是提呈作用较B细胞强的永生化细胞 ,可通过对自体淋巴细胞的刺激作用以及负载抗原后刺激活性的变化 ,来比较这两类细胞的生物学特性。本研究比较了二者对肝癌抗原的提呈作用。1　材料与方法1 1　研究对象　健康成年人。1 2　主要试剂　重组人粒细胞巨噬细胞集落刺激因子 (rhGM CSF) ,重组人白细胞介素 4 (rhIL 4 )购于TEPROTECH公司 ;人白细胞介素 2 (Interleukin 2 )购于北京医科大学免疫系 ;3 H 标记甲基胸腺嘧啶…     

慢性乙型肝炎患者外周血树突状细胞功能状态与HBV载量的关系

目的：探讨慢性乙型肝炎（CHB）患者外周血树突状细胞功能状态与HBV载量的关系。方法：采集23例CHB患者和8例健康人的抗凝外周静脉血，分离外周血单个核细胞（PBMCs），在重组人白细胞介素4和重组人粒细胞-巨噬细胞集落刺激因子的作用下培养使DCs增殖、成熟，以间接免疫荧光流式细胞技术分别检测DCs表面CD80、CD86、HLA-DR及ICAM-1的表达；以ELISA法检测DCs培养上清液中IL-12的水平；将培养成熟的DCs与HBsAg共同孵育，用丝裂霉素C处理后再与自体PBMCs共同培养，在培养结束前12小时加入^3H-TDR，收集细胞，以β液闪计数仪测定cpm值；同期用定量聚合酶链反应技术测定CHB患者外周血HBV载量。结果：患者DCs表面CD86、HLA-DR和ICAM-1的表达水平，DCs的抗原提呈能力及其分泌IL-12的水平均显著低于健康对照组；CD80、CD86、HLA-DR及ICAM-1的表达与HBV载量呈显著负相关关系（分别为P〈0．01、P〈0．01、P〈0．001和P〈0．001）；DCs的抗原提呈能力及其分泌IL-12的水平也与HBV载量呈显著负相关关系（分别为P〈0．001和P〈0．01）。结论：CHB患者外周血DCs的成熟和功能存在障碍，DCs的功能状态与血液中HBV的载量密切相关，并可能对HBV的清除产生重要的影响。     

EB病毒蛋白对免疫球蛋白产生的调节作用

目的检验EB病毒(Epstein-Barr Virus,EBV)蛋白对培养的人B细胞产生免疫球蛋白(Immunoglobulin,Ig)的影响.方法用UV灭活和热处理的EBV刺激培养的人脐带血B细胞,流式细胞仪检测UV灭活EBV组细胞CD5、CD3、CD4和CD8的表达,ELISA法检测培养上清中IgG和IgM,同时与EBV转化B细胞产生的IgG和IgM 作对比.结果第14天未检测到T细胞,CD5+B 细胞占43%;28天时CD5+B细胞占47%.UV灭活EBV组第10、18、22和26天IgG A值与对照组相比有显著差异(P＜0.05),第10天以后各时间点IgM A值与对照组相比有显著差异(P＜0.05).EBV转化培养B细胞40天,IgG和IgM A值与同期其它各组有显著差异(P＜0.05).结论EBV蛋白有诱导Ig产生的作用.     

卵巢癌细胞培养上清诱导CD4+CD25-T细胞分化为CD4+CD25+调节性T细胞

目的研究卵巢癌细胞培养上清液是否能诱导外周血CD4^＋CD25^- T细胞转变为CD4^＋CD25^＋调节性T细胞。方法将外周血CD4^＋CD25^- T细胞分离后，对照组用CD3和CD28单抗活化，实验组在对照基础上加用卵巢癌细胞株SKOV3培养上清，72h后分离各组的CD25^＋和CD25^-T细胞，溴化脱氧尿嘧啶掺入标记法测定增殖能力及对静息的自体同源CD4^＋CD25^- T细胞的增殖抑制能力，流式细胞仪测定细胞糖皮质激素诱发型TNF受体（glucocorticoid-induced TNFR,GITR）与CTLA-4分子的表达，RT-PCR检测细胞卿mRNA的表达。结果与对照组相反，实验组的CD4^＋CD25^＋T细胞具有免疫抑制功能，自身增殖能力下降，GITR和CTLA-4分子的表达和CD4^＋CD25^＋调节性T细胞相似，并被诱导表达转录因子Foxp3 mRNA。结论卵巢癌细胞分泌的可溶性物质能诱导外周血CD4^＋CD25^-T细胞转化为CD4^＋CD25^＋调节性T细胞。     

转染自体胃癌细胞总RNA的树突状细胞诱导个体化免疫治疗的体外实验

目的探讨转染自体胃癌细胞总RNA的树突状细胞(DC)体外介导抗胃癌的免疫效应。方法制备短期培养的原代胃癌细胞。用rhGM-CSF、rhIL-4和TNF-α体外诱导胃癌患者外周血单个核细胞(PBMC)中DC的发育和成熟,并转染自体肿瘤细胞总RNA,激活自体T细胞产生CTL,用CCK-8试剂盒检测CTL的杀伤活性。应用流式细胞术及混合淋巴细胞培养技术检测DC的免疫功能状态。用ELISA法测定IL-12和INF-γ的水平。结果转染自体肿瘤细胞总RNA的成熟DC,不仅可高表达MHC-I、II类分子及CD80、CD83和CD86协同刺激分子,并可获得高效刺激自体或异体T细胞增殖的能力。转染RNA的成熟DC,分泌IL-12的水平及其刺激产生的CTL培养上清液中INF-γ的水平显著高于单纯成熟DC及未成熟DC;且CTL对自体胃癌细胞的杀伤率显著高于异体组。结论转染自体胃癌细胞总RNA的成熟DC能够体外诱导产生对自体肿瘤细胞具有高度抗原特异性杀伤活性的CTL。     

胃肠肿瘤患者外周血树突状细胞功能失调与CD4+CD25+T细胞失衡的临床意义

目的：探讨胃肠肿瘤（GIC）患者外周血单个核细胞（PBMCs）来源树突状细胞（DCs）和CD4^＋CD25^＋T细胞（Tregs）的免疫功能状态，以及其与肿瘤临床病理分期和手术的关系。方法：收集早期胃肠癌（Ⅰ／Ⅱ期）患者术前、术后第7天以及晚期癌（Ⅲ／Ⅳ期）患者外周血，以健康成人外周血为对照。提取单个核细胞（PBMCs），流式细胞术（FACS）分别检测Tregs占CD4^＋T细胞的比例。PBMCs经贴壁法分离提取DCs，经rhGM。CSF、rhIL-4体外扩增培养至第5天，获得未成熟DCs（imDCs），FACS检测表型；imDCs经rhTNF-α诱导培养至第7天，获得成熟DCs（mDCs），MTT法和ELISA法分别检测mDCs与自体T细胞混合培养时mDCs刺激T细胞增殖能力以及上清液中IFN-γ的含量。结果：晚期胃肠癌患者imDCs表型HIA-DR、CD80及CD86均显著低于健康成人和早期癌患者（P〈0．01）；早期胃肠癌术后第7天患者imDC8表型HIA-DR及CD86表达显著低于健康成人（P〈0．05）。晚期胃肠癌患者mDCs刺激自体T细胞增殖及分泌IFN-γ的能力与健康成人相比均有所减弱（P=0．073，P=0．182）CD4^＋T细胞中Tregs的比例显著低于健康成人和早期癌患者（P〈0．001）；早期胃肠癌患者术后Tregs比例略低于术前（P=0．148）及健康成人（P=0．068）。HLA-DR、CD86表达与Tregs比例呈负相关性。结论：胃肠肿瘤患者尤其晚期和术后患者外周血DCs功能失调以及Tregs失衡可能和机体抗肿瘤细胞免疫耐受密切相关。     

Human antigen-presenting cell/tumour cell hybrids stimulate strong allogeneic responses and present tumour-associated antigens to cytotoxic T cells in vitro

Most tumours do not stimulate effective antitumour immune responses in vivo. In order to enhance the immunogenicity of human tumour cells, we fused a variety of tumour cell lines with an Epstein-Barr virus transformed B-lymphoblastoid cell line (EBV B-LCL) in vitro, to produce stable hybrid cells. Hybrid cell lines showed a marked increase in their ability to stimulate primary allogeneic T-cell responses in vitro, as compared with the parent tumour cells. The hybrid cells induced proliferation of naive (CD45RA+) as well as memory (CD45RO+) T lymphocytes, and both CD4+ and CD8+ subpopulations of T cells were directly stimulated. The stimulatory hybrids expressed human leucocyte antigen (HLA) class I and II, and a wide range of surface accessory molecules, including the T-cell co-stimulatory ligand molecules CD40, CD80 (B7.1) and CD86 (B7.2), the expression of which was required for optimal stimulation of T-cell responses. Fusion of the EBVB-LCL with a melanoma cell line (518.A2) yielded hybrid cells that expressed the melanoma-associated antigens MAGE-1 and MAGE-3, and presented these antigens to antigen-specific, HLA class I-restricted cytotoxic T-lymphocyte clones with greater efficiency than the parent melanoma cell line. These findings suggest that the generation of human antigen-presenting cell/tumour cell hybrids offers promise as an approach to cancer immunotherapy.     

A human-human hybridoma producing cytotoxic antibody to HLA-B15, cross-reacting with B17, B5, B35 and B18

Mononuclear blood cells from a multiparous woman were transformed with Epstein Barr virus, and a cell line (Tr2D8) producing anti-HLA antibody was obtained. This cell line was immortalized by hybridization to the human fusion partners KR4 and KR12. While the EBV line died after 7 months, the hybridomas have remained stable for 13 months. The EBV line supernatant (40 micrograms IgM/ml) lysed peripheral blood mononuclear cells (PBMC) bearing B15, B17, B5 and B35. Consistent lysis of B18 bearing cells was only observed with lymphoblastoid cell lines. The supernatant from the Tr2D8 (EBV line X KR4) hybridoma (2.7 micrograms IgM/ml) only lysed B15 bearing PBMC. At a concentration of 13.5 micrograms IgM/ml, the hybridoma antibody lysed lymphoblastoid cell lines bearing B15, B17, B5, B35 and B18.     

CpG基序联合EB病毒建立永生化B淋巴母细胞系

目的 体外建立慢性乙型肝炎患者永生化的B淋巴母细胞系(LCLs).方法 用EB病毒感染自慢性乙型肝炎患者外周血中分离的单个核细胞(PBMC),加入CpG DNA免疫调节基序以诱导B淋巴细胞增殖,环胞菌素A(CysA)抑制T淋巴细胞的活性.光学显微镜下观察LCLs的形态特征,利用流式细胞术分析LCLs膜表面分子CD19和CD23的表达水平.结果 46例患者PBMC经EBV感染4周后,42例转化成永生化B淋巴母细胞系,成功率为91.3%.转化后的B淋巴母细胞体积增大积聚成团,可进一步分裂增殖并长期传代培养.结论 CpG免疫调节基序联合EBV感染人PBMC,提高转化效率,转化后的LCL保持了成熟B淋巴细胞的生物学特性,可作为体外研究HBV特异性免疫应答的刺激细胞和靶细胞.     

Epstein-Barr virus interactions with human lymphocyte subpopulations: virus adsorption, kinetics of expression of Epstein-Barr virus-associated nuclear antigen, and lymphocyte transformation.

In order to further understand Epstein-Barr virus (EBV)-lymphocyte interactions, we investigated a chain of events including: (i) EBV binding to human lymphocyte subpopulations; (ii) the earliest appearance of EBV-determined nuclear antigen (EBNA) in the lymphocytes after EBV infection; and (iii) establishment of continuous lymphoblastoid cell lines (LCL) by infecting with EBV different types of lymphocyte preparations from the same as well as from different donors. By using direct membrane immunofluorescence assay, we found that only a small fraction of human peripheral blood and cord blood lymphocytes (CBL), and possibly less than 31% of the T cell-depleted lymphocyte population, carry receptors for P3HR-1 strain of EBV. The number of cells carrying receptors for EBV did not vary considerably among different blood lymphocyte populations from several normal donors. EBV adsorption on lymphocyte subpopulations showed that purified thymus-dependent (T) cells and thymocytes did not adsorb EBV, in contrast to T cell-depleted lymphocyte populations and lymphoid cells from fetal liver and spleen. In CBL infected with EBV strain B95-8, EBNA was detected by anti-complement immunofluorescence as early as 18 h after infection. This indicates that EBNA is the earliest detectable EBV-determined intracellular antigen to appear after infection and before or during lymphocyte transformation by EBV. Transformation was observed only in lymphocyte cultures containing detectable thymus-independent B cells but not in cultures of purified T cells. With one exception (es-b-1), all the EBV-transformed LCL from different origins carried surface-bound immunoglobulins (a B cell marker). These included also the 10 LCL obtained by infecting cultures of adherent cells from different donors. With regard to its surface markers, ES-B-1 appeared to be an exceptional EBV genome-carrying line, and it also lacked the ability to form spontaneous rosettes with sheep erythrocytes (a T cell marker). Therefore, it is possible that ES-B-1 was derived from an atypical B cell or B cell precursor or from a so-called "null cell" transformed by EBV.     

Inhibition of cell growth and Epstein-Barr virus reactivation by CD40 stimulation in Epstein-Barr virus-transformed B cells

The CD40 molecule plays important roles in B cell activation, proliferation, and immunoglobulin (Ig) class switching. In Epstein-Barr virus (EBV)-transformed lymphoblastoid cell lines (LCL), CD40 mediates growth inhibition and EBV reactivation via the CD40 signaling pathways. CD40 cross-linking with a monoclonal antibody arrests cell growth in G1 and induces expression of p27kip1 cyclin-dependent kinase inhibitor. CD40 cross-linking also induces EBV reactivation, as detected by the induction of EBV-specific early antigen, immediate early BZLF1 RNA, and its protein product ZEBRA. These results support hypotheses that the proliferation of EBV-infected B cells in vivo can be inhibited by interactions with the CD40 ligand on activated helper T cells, and latent EBV is reactivated via the signaling pathways controlled by CD40 interactions.     

Human T cell responses to beta-galactosidase.

The peripheral blood of most normal individuals has been shown to contain T cells that respond to beta-galactosidase (beta-Gal), presumably as a result of natural priming. Three T cell clones (clones 1,2,4) specific for beta-Gal were isolated from peripheral blood mononuclear cells (PBMC) after pretreatment with leucine methyl ester (LeuOMe); a fourth clone from the same individual was isolated from untreated cells. All four clones were CD4+ CD8- alpha beta TcR+ and clone 1 was additionally shown to be cytotoxic. Epstein-Barr virus (EBV) transformed B cell lines were derived from LeuOMe-treated or untreated PBMC and used to study the efficiency of presentation of beta-Gal to one of the clones. The results indicated that B cells transformed after LeuOMe treatment presented beta-Gal at lower concentrations than untreated controls. beta-Gal would therefore appear to be a highly suitable model antigen for studies of immunoregulation in humans.     

Identification of CD8+ T-cell epitopes specific for immediate-early transactivator Rta of Epstein-Barr virus

Nasopharyngeal carcinoma (NPC) is a human epithelial tumor with a high incidence in Southern Chinese population, with contributions from Epstein-Barr virus (EBV), human leukocyte antigen (HLA), and environmental factors to its etiology. It has been shown previously that the recognition of immediate-early transactivator Rta of EBV by CD8+ T cells may have a significant impact on controlling EBV and, indirectly, NPC. The current study used two computer-aided prediction methods and competition-based HLA-peptide binding assays to screen for HLA B2704/B4601/B5801 restricted T-cell epitopes derived from Rta. HLA tetrameric complexes containing these potential T-cell epitopes were synthesized. Rta-specific CD8+ T-cell responses in healthy virus carriers were then defined by these tetramers and IFN-gamma ELISPOT assays. We clearly demonstrated that healthy virus carriers have detectable Rta-specific CD8+ T cells restricted by B2704 in the circulation. However, there were no B4601/B5801 tetramer-reactive T cells specific for Rta in the peripheral blood of matched/mismatched donors. On the other hand, B4601 tetramers containing the computer-predicted B4601 binder EBNA3A (318-326) showed detectable tetramer-reactive T cells in the circulation of healthy virus carriers. topes also elicited IFN-gamma responses as detected by ELISPOT.     

Effective antigen presentation to helper T cells by human eosinophils

Although eosinophils are inflammatory cells, there is increasing attention on their immunomodulatory roles. For example, murine eosinophils can present antigen to CD4⁺ T helper (Th) cells, but it remains unclear whether human eosinophils also have this ability. This study determined whether human eosinophils present a range of antigens, including allergens, to activate Th cells, and characterized their expression of MHC class II and co‐stimulatory molecules required for effective presentation. Human peripheral blood eosinophils purified from non‐allergic donors were pulsed with the antigens house dust mite extract (HDM), Timothy Grass extract (TG) or Mycobacterium tuberculosis purified protein derivative (PPD), before co‐culture with autologous CD4⁺ Th cells. Proliferative and cytokine responses were measured, with eosinophil expression of HLA‐DR/DP/DQ and the co‐stimulatory molecules CD40, CD80 and CD86 determined by flow cytometry. Eosinophils pulsed with HDM, TG or PPD drove Th cell proliferation, with the response strength dependent on antigen concentration. The cytokine responses varied with donor and antigen, and were not biased towards any particular Th subset, often including combinations of pro‐ and anti‐inflammatory cytokines. Eosinophils up‐regulated surface expression of HLA‐DR/DP/DQ, CD80, CD86 and CD40 in culture, increases that were sustained over 5 days when incubated with antigens, including HDM, or the major allergens it contains, Der p I or Der p II. Human eosinophils can, therefore, act as effective antigen‐presenting cells to stimulate varied Th cell responses against a panel of antigens including HDM, TG or PPD, an ability that may help to determine the development of allergic disease.     

Expression of B7 (CD80) and CD40 antigens and the CD40 ligand in Hodgkin's disease is independent of latent Epstein-Barr virus infection

Aim-To examine the expression of CD40 and B7 (CD80) antigens and the CD40 ligand in Hodgkin's disease.Methods-Antigen and ligand expression was studied in 17 cases of Hodgkin's disease using immunohistochemistry. The study included 11 cases of Hodgkin's disease in which latent Epstein-Barr virus (EBV) infection could be demonstrated within tumour cells by in situ hybridisation for the EBV encoded early RNAs (EBERs).Results-In all cases, irrespective of EBV status, Reed-Sternberg cells and their variants (HRS cells) showed strong expression of both B7 and CD40 antigens. CD40 ligand expression was not shown in HRS cells but was confined to a subset of small lymphocytes some of which were seen to be in intimate contact with HRS cells.Paraffin wax sections from a further 60 cases of Hodgkin's disease were examined for CD40 and EBER expression alone. The CD40 antigen was identified in HRS cells in all of these cases irrespective of EBER expression.Conclusions-As CD40 and B7 expression are features of professional antigen presenting cells, these results provide further evidence that HRS cells may have antigen presenting properties and that this may contribute to the characteristic recruitment and activation of non-malignant lymphocytes which is a feature of Hodgkin's disease. The ability of HRS cells to activate T(h) cells may in turn contribute to their own survival through the induction of the gp39/CD40 pathway.