DC肿瘤融合瘤苗抗肿瘤效应的实验研究

目的:观察DC与肿瘤细胞融合后的瘤苗体内诱导的抗肿瘤免疫应答以及对荷瘤小鼠的治疗作用.方法:应用免疫磁珠分选和贴壁培养方法收集融合细胞,应用3H-TdR掺入法、4h51Cr释放法观察T细胞增殖反应的能力和CTL活性,并观察瘤苗对荷瘤小鼠保护性免疫反应和免疫治疗作用.结果:DC肿瘤融合瘤苗具有强烈的激活T细胞增殖和抗原提呈的能力,在体外、体内诱导出更强的特异CTL细胞毒活性,使免疫小鼠产生一定的免疫保护作用,抵抗Hepa1-6肝癌细胞的再次攻击,使治疗的小鼠肿瘤的生长明显缓慢,具有更明显的治疗作用.结论:DC与肿瘤细胞融合后进行体内免疫和治疗,能诱导出显著的抗肿瘤免疫反应,为DC介导的肿瘤免疫治疗开辟了新的途径.     

MIP-1β基因修饰增强肿瘤相关抗原致敏树突状细胞的抗肿瘤免疫效果

目的:探讨通过增强树突状细胞(dendritic cells,DC)与T细胞的相互作用来进一步增强DC介导的抗肿瘤免疫效果.方法:体外培养的小鼠骨髓DC体外经携带人MIP-1β基因的重组腺病毒(adenovirus expressing human macrophoge inflammatory protein-1 beta,AdhMIP-1β)转染后(MIP-1β-DC),用小鼠CT26结肠腺癌细胞相关抗原冲击致敏,然后免疫正常同系小鼠,观察其体内诱导的细胞毒性T淋巴细胞(cytotoxic T lymphocyte,CTL)的保护性免疫反应;通过体内阻断试验探讨免疫细胞亚群及免疫分子在DC诱导抗肿瘤免疫应答中的作用.结果:经抗原致敏的MIP-1β-DC能更有效地诱导特异CTL活性,能使免疫动物产生更有效的免疫保护作用,抵抗肿瘤细胞的攻击.通过对其抗肿瘤免疫机理的分析发现,CD4 、CD8 T细胞共同参与了经抗原致敏的MIP-1β-DC介导的抗肿瘤免疫反应,是主要的抗瘤效应细胞,NK细胞作用不明显.结论:通过基因修饰增强树突状细胞对T细胞的体内趋化活性,能更有效地诱导抗肿瘤免疫反应,为树突状细胞介导的肿瘤免疫基因治疗开辟了新的途径.     

MIP-1β基因修饰增强肿瘤相关抗原致敏树突状细胞的抗肿瘤免疫效果

目的：探讨通过增强树突状细胞(dendritic cells, DC)与T细胞的相互作用来进一步增强DC介导的抗肿瘤免疫效果。方法：体外培养的小鼠骨髓DC体外经携带人MIP1β基因的重组腺病毒(adenovirus expressing human macrophoge inflammatory protein1 beta, AdhMIP1β)转染后(MIP1βDC)，用小鼠CT26结肠腺癌细胞相关抗原冲击致敏，然后免疫正常同系小鼠，观察其体内诱导的细胞毒性T淋巴细胞(cytotoxic T lymphocyte, CTL)的保护性免疫反应；通过体内阻断试验探讨免疫细胞亚群及免疫分子在DC诱导抗肿瘤免疫应答中的作用。结果：经抗原致敏的MIP1βDC能更有效地诱导特异CTL活性，能使免疫动物产生更有效的免疫保护作用，抵抗肿瘤细胞的攻击。通过对其抗肿瘤免疫机理的分析发现，CD4+、CD8+ T 细胞共同参与了经抗原致敏的MIP1βDC介导的抗肿瘤免疫反应，是主要的抗瘤效应细胞，NK细胞作用不明显。结论：通过基因修饰增强树突状细胞对T细胞的体内趋化活性，能更有效地诱导抗肿瘤免疫反应，为树突状细胞介导的肿瘤免疫基因治疗开辟了新的途径。     

IL-18基因修饰增强肿瘤细胞裂解物致敏的树突状细胞的抗肿瘤效应

目的:观察经肿瘤细胞裂解物致敏的白细胞介素18(IL-18)基因修饰的树突状细胞(DC)体内诱导的抗肿瘤免疫应答反应.方法:体外培养的小鼠骨髓树突状细胞经IL-18重组腺病毒感染后(IL18-DC),再经Hepal-6肝癌细胞裂解物冲击致敏后通过皮下注射用于荷瘤小鼠的治疗.用ELISA检测细胞因子,4 h51Cr释放法检测NK细胞活性及CTL杀伤活性.结果:致敏IL18-DC组体内诱导NK细胞活性与未致敏IL18-DC组无明显差别(P＞0.05),但明显高于致敏DC组和DC组(均P＜0.01);致敏IL18-DC组体内诱导特异性CTL杀伤活性明显高于IL18-DC组、致敏DC组和DC组(均P＜0.01);致敏IL18-DC组免疫治疗作用明显优于未致敏IL18-DC组、致敏DC组和DC组(均P＜0.01).结论:肿瘤细胞裂解物致敏的IL-18基因修饰的DC疫苗进行体内免疫治疗,能诱导出显著的抗肿瘤免疫反应,为DC介导的肿瘤基因治疗开辟了新的途径.     

GM-CSF/IL-4基因修饰的瘤苗不同的免疫途径诱导不同免疫反应的观察

对细胞因子基因修饰瘤苗的研究表明,IL-2、IL-4、IFN-γ、GM-CSF等一系列细胞因子基因以不同载体转入肿瘤细胞制成瘤苗后皮下免疫小鼠,均可增强机体抗肿瘤免疫力,其机制可能是由于瘤苗分泌的细胞因子促进了免疫细胞对肿瘤抗原的识别、提呈及对肿瘤细胞的杀伤能力.有文献报道,逆转录病毒介导的GM-CSF和IL-4共同转染瘤苗可以有效激发机体抗肿瘤免疫力,为探讨不同途径瘤苗免疫后机体的免疫反应,我们采用皮下、腹腔、脾内、静脉四种途径接种GM-CSF、IL-4基因双重转染的小鼠红白血病细胞FBL-3瘤苗,发现免疫途径不同,所激发的免疫应答类型不同,诱导机体生成的免疫力不同,提示某些瘤苗应用时应选择适当的免疫途径.     

脐血树突状细胞介导的食管癌瘤苗体内抗癌效应

背景与目的:用杂交瘤技术制备脐血树突状细胞(DC)和食管癌细胞的融合瘤苗,探讨其在体内诱导抗肿瘤效应.材料与方法:分离脐血CD34+干细胞诱导扩增为成熟DC,与EC109细胞经聚乙二醇(PEG)法融合;免疫磁珠法筛选EC109-DC,鉴定瘤苗表型和致瘤性;观察该瘤苗的体内成瘤性、保护性免疫反应和免疫治疗效果.结果:融合瘤苗可体外生长,并高表达CD80、CD83、CD86和叶酸受体(FR);瘤苗接种小鼠体内未见肿瘤形成;经瘤苗免疫的小鼠,肿瘤生长的潜伏期较对照组明显延长(P＜0.05),肿瘤的大小和肿瘤重量均明显小于对照组(P＜0.05).用融合瘤苗治疗的荷瘤小鼠,肿瘤的大小和重量也均明显小于对照组(P＜0.05).结论:融合瘤苗EC109-DC同时表达EC109和DC特异性抗原,无体内致瘤性,对EC109细胞的攻击有明显的抵抗作用,对治疗荷瘤小鼠有一定的作用.     

放疗或化疗诱导淋巴细胞减少联合免疫重建和瘤苗免疫

目的利用淋巴细胞减少期T细胞发生增殖活化的原理,以全身照射或环磷酰胺引起淋巴细胞减少,联合免疫重建及肿瘤疫苗免疫,以增强机体的肿瘤特异性免疫反应。方法分别以放疗或化疗（环磷酰胺）引起小鼠淋巴细胞减少,然后输入同系小鼠的未致敏脾细胞,建立免疫重建的淋巴细胞减少小鼠模型（RLM）。用黑色素瘤细胞F10对前者行免疫．肿瘤攻击实验,并行T细胞亚群清除试验。而化疗-RLM-免疫模型的抗肿瘤免疫反应效果通过过继免疫治疗检测。免疫用瘤苗为GMCSF修饰的黑色素瘤细胞D6-G6。免疫后9～10d,采集肿瘤疫苗接种部位的引流淋巴结,制备效应T细胞,然后过继回输给荷瘤3d（D5）的小鼠。2周后处死小鼠,计数肺转移灶数目。结果63．2％的放疗-RLM-免疫组小鼠可对肿瘤攻击产生抵抗,显著高于正常-免疫组（16．7％,P〈0．0001）。CD8^＋T细胞是介导抗肿瘤保护性免疫的主要效应细胞。延长免疫重建和瘤苗接种之问的间隔可削弱保护性抗肿瘤免疫。化疗-RLM-免疫组效应T细胞的在体抗肿瘤活性显著强于正常．免疫组。结论在放、化疗引起的淋巴细胞减少期进行瘤苗免疫,有助于打破机体对肿瘤的免疫耐受,增强抗肿瘤免疫反应。     

人巨噬细胞炎性蛋白-1β基因修饰肿瘤细胞的体内致瘤性和瘤苗效果

目的 探讨人巨噬细胞炎性蛋白-1β(hMIP-1β)基因修饰小鼠结肠腺癌CT26细胞的致瘤性和瘤苗免疫效果.方法 通过重组腺病毒载体介导,将hMIP-1β基因导入CT26细胞中,X-gal染色法检测基因转染效率;采用酶联免疫吸附试验(ELISA)法检测hMIP-1β基因修饰CT26细胞培养上清中hMIP-1β的含量;采用Boyden趋化小室法检测培养上清对CD4+ T细胞、CD8+ T细胞、NK细胞和未成熟树突状细胞(imDC)的趋化作用.BALB/c小鼠皮下接种hMIP-1β基因修饰的CT26细胞,观察其体内致瘤性的改变和对免疫细胞的趋化作用;制备hMIP-1β基因修饰的CT26细胞瘤苗并免疫BALB/c小鼠,观察其诱导免疫细胞的杀伤活性和保护性免疫反应.结果 腺病毒载体可介导hMIP-1β基因转染CT26细胞和表达,X-gal染色的阳性率可达95.0%以上.在培养上清中hMIP-1β水平为980 pg/ml细胞,并对CD4+ T细胞、CD8+ T细胞、NK细胞和imDC有显著的趋化作用,与转染对照基因LacZ的CT26细胞及野生型CT26细胞比较,差异有统计学意义(P＜0.01).体内致瘤实验显示,hMIP-1β基因修饰的CT26细胞皮下接种后,成瘤率降低,肿瘤生长速度减慢,肿瘤内可见明显坏死灶,坏死灶内和周围可见较多淋巴细胞浸润.hMIP-1β基因修饰的CT26细胞瘤苗免疫小鼠能有效诱导肿瘤特异性CTL活性和非特异性NK活性,产生明显的免疫保护作用,可抵抗肿瘤细胞的再攻击.结论 hMIP-1β基因修饰的CT26细胞致瘤性显著下降,其瘤苗可诱导强烈的抗肿瘤免疫反应,提示hMIP-1β基因修饰瘤苗有望成为更有效的抗肿瘤免疫治疗手段.     

肝癌（H22）固化瘤苗对荷瘤小鼠的主动免疫作用

目的 观察肝癌(H_(22))固化瘤苗对荷瘤小鼠的主动免疫作用。方法 将小鼠原发性肝癌细胞(H_(22))经1000GYγ射线照射灭活,经65℃10min条件下制备成固化瘤苗,免疫荷瘤鼠,观察小鼠生存时间,瘤体直径、瘤重、脾及胸腺重要指标。结果 表明固化瘤苗对荷瘤鼠有主动特异性免疫治疗作用。结论 固化瘤苗可较好地诱发机体的免疫反应,其作为“癌疫苗”疗法可有潜在的应用价值。     

肿瘤浸润性树突状细胞的研究进展

树突状细胞(DCs)是最具潜能的抗原提呈细胞，它能激活初始型T细胞，在启动抗瘤免疫应答中扮演着重要角色。肿瘤浸润性树突状细胞(TIDCs)反映了荷瘤宿主的抗瘤免疫能力，其浸润密度可能与肿瘤预后有关。TIDC是功能低下或无功能的树突状细胞，肿瘤细胞分泌的免疫抑制因子对其表型特征的改变可能是致使其功能低下的原因。以上研究为DC介导的肿瘤免疫治疗提供了理论基础，并指导人们从不同途径利用DC诱导抗瘤免疫反应，从而达到治疗肿瘤的目的。     

Natural killer cells play a critical role in the immune response following immunization with melanoma-antigen-engineered dendritic cells

Tumor antigen gene-modified dendritic cells (DC) generates robust antigen-specific protective antitumor responses. Though the role of CD4 positive and CD8 positive cells in the immunological response to gene-modified DC has been well-characterized, the role of NK cells in this response has been somewhat less clear. Owing to the significant contribution of innate immunity in other model systems, we postulated that NK cells would hold a critical position in the generation of an immune response following immunization with tumor antigen-engineered DC. Immunization with MART-1 melanoma antigen-engineered DC in C57BL/6 mice resulted in the generation of antigen-specific cytotoxic T lymphocytes and in vivo protective responses to the murine B16 melanoma. These responses were dependent on the presence of functional NK cells, although NK cells alone were not sufficient in generating protective responses. Adoptive transfer of NK cells into an NK-deficient but T-cell-competent environment restored the protective response to gene-modified DC immunization. In conclusion, protective immunity after tumor antigen gene-modified DC immunization requires collaboration between CD4+ and CD8+ T cells and NK cells.     

Induction of protective immunity to RM-1 prostate cancer cells with ALVAC-IL-2/IL-12/TNF-alpha combination therapy

Human prostate cancers characteristically express low levels of major histocompatibility complex (MHC) Class I, which makes it challenging to induce protective antitumor responses involving T cells. Here we demonstrate that a whole cell tumor vaccine can induce protective T cell immunity to a low MHC Class I-expressing mouse prostate cancer cell line, RM-1. ALVAC recombinant canarypox viruses encoding interleukin-2, interleukin-12 and tumor necrosis factor-alpha were used to create therapeutic vaccines in 2 different ways. The RM-1 cells were pre-infected in vitro with the viruses prior to injection (pre-infection vaccine) or the RM-1 cells were injected alone, followed by the viruses (separate injection vaccine). The vaccines were each tested subcutaneously or intradermally. The pre-infection vaccine resulted in 100% clearance of primary tumors, whereas intradermal delivery of the separate injection vaccine cleared 40-60% of primary tumors. Despite the highly efficient primary tumor clearance by the pre-infection vaccine, only the separate injection vaccine generated protection upon rechallenge. Tumor-free survival induced by the separate injection vaccine required natural killer (NK) cells, CD4(+), and CD8(+) T cells. None of these cells alone were sufficient to induce tumor-free survival to the primary challenge, demonstrating an important cooperativity between NK cells and T cells. Secondary clearance of tumors also required NK and CD8(+) T cells, but not CD4(+) T cells. We report for the first time the generation of T cell immunity to the RM-1 prostate cancer cell line, demonstrating that it is possible to generate protective T cell immunity to a MHC I-low expressing tumor.     

Intratumoral administration of immature dendritic cells following the adenovirus vector encoding CD40 ligand elicits significant regression of established myeloma

Our previous study showed that J558 myeloma cells engineered CD40L lost their tumorigenicity in syngeneic mice, and the inoculation of J558/CD40L tumor cells further led to the protective immunity against wild tumors. In the present study, we investigated whether the vaccine can exert more efficient antitumor immunity by combination with adenovirus mediated CD40L gene therapy and immature dendritic cells (iDCs). The results demonstrated that intratumoral administration of iDCs 2 days after AdVCD40L injection, not only significantly suppressed the tumor growth, but also eradiated the established tumors in 40% of the mice. The potent antitumor effect produced by the combination therapy correlated with high expression of MHC, costimulatory and Fas molecules on J558 cells, which was derived from CD40L transgene expression. In addition, transgene CD40L expression could dramatically induce J558 cell apoptosis. Effectively capturing apoptotic bodies by iDCs in vivo could induce DC maturation, prime tumor-specific CTLs and tend to Th1-type immune response. Finally, in vivo depletion experimentation suggested both CD4+ and CD8+ T cells were involved in mediating the antitumor immune responses of combined treatment of AdVCD40L and iDCs, with CD8+ T cells being the major effector. These findings could be beneficial for designing strategies of DCs vaccine and CD40L for anticancer immunotherapy.     

Targeting the immunoregulator SRA/CD204 potentiates specific dendritic cell vaccine-induced T-cell response and antitumor immunity

Although dendritic cell (DC) vaccines offer promise as cancer immunotherapy, further improvements are needed to amplify their clinical therapeutic efficacy. The pattern recognition scavenger receptor SRA/CD204 attenuates the ability of DCs to activate CD8(+) T-cell responses. Therefore, we examined the impact of SRA/CD204 on antitumor responses generated by DC vaccines and we also evaluated the feasibility of enhancing DC vaccine potency by SRA/CD204 blockade. DCs from SRA/CD204-deficient mice were more immunogenic in generating antitumor responses to B16 melanoma, compared with DCs from wild-type mice. Similarly, siRNA-mediated knockdown of SRA/CD204 by lentiviral vectors improved the ability of wild-type DCs to stimulate the expansion and activation of CD8(+) T cells specific for idealized or established melanoma antigens in mice. Using SRA/CD204-silenced DCs to generate antigen-targeted vaccines, we documented a marked increase in the level of antitumor immunity achieved against established B16 tumors and metastases. This increase was associated with enhanced activation of antigen specific CTLs, greater tumor infiltration by CD8(+) T cells and NK cells, and increased intratumoral ratios of both CD4(+) and CD8(+) T-effector cells to CD4(+)CD25(+) T-regulatory cells. Our studies establish that downregulating SRA/CD204 strongly enhances DC-mediated antitumor immunity. In addition, they provide a rationale to enhance DC vaccine potency through SRA/CD204-targeting approaches that can improve clinical outcomes in cancer treatment.     

Fractalkine transgene induces T-cell-dependent antitumor immunity through chemoattraction and activation of dendritic cells

Fractalkine (FK, also called neurotactin or CX3CL1) is a CX3C chemokine that can chemoattract T lymphocytes, monocytes and NK cells. In our study, we investigated the induction of antitumor response by FK gene transfer. FK gene-modified 3LL lung carcinoma cells (3LL-FK) could both secrete soluble form and express membrane-bound form of FK. The tumor growth of 3LL-FK was decreased. Vaccination with 3LL-FK was effective in the induction of protective immunity and CTL. In vivo depletion analysis demonstrated that CD8(+) T cells are the main participating cells of the antitumor response. Obvious infiltrations of CD8(+) T cells, CD4(+) T cells and dendritic cells (DC) were observed in the tumor sites, suggesting that 3LL-FK might induce antitumor immunity through chemoattraction and activation of T cells and DC. Then we investigated the chemoattraction and activation of DC by 3LL-FK. Chemotaxis assay showed that the supernatants of 3LL-FK could chemoattract immature DC, which were found to express FK receptor CX3CR1, and the immature DC could obviously adhere to 3LL-FK. Adherence of DC to 3LL-FK resulted in phenotypic maturation and upregulated IL-12 secretion of DC, and more strong stimulation of allogeneic T-cell proliferation by DC. The increased production of IL-2 and IFNgamma in 3LL-FK tumor tissue was also observed. Our data suggested that FK gene transfer to tumor cells could induce T-cell-dependent antitumor immunity through chemoattraction and activation of DC.     

Interleukin 18 transfection enhances antitumor immunity induced by dendritic cell-tumor cell conjugates

Dendritic cell (DC)-based tumor vaccine represents a promising approach to the immunotherapy of malignant tumors. We prepared a novel type of DC-based vaccine, stable conjugates of DCs and EL4 cells transduced with cDNA of OVA (E.G7). Immunization with DC-E.G7 conjugates led to generation of T helper (Th) 1 cytokine-producing cells, antigen-specific CD8(+) T cells, and strong antitumor immunity that is dependent on both CD4(+) T cells and CD8(+) T cells. To further increase the potency of the vaccine, interleukin 18-transfected DCs were used to prepare the IL18DC-E.G7 conjugates. Immunization with such conjugates significantly increased the production of Th1 cytokine-producing cells and the number of antigen-specific CD8(+) T cells, as well as stronger antitumor immunity. Furthermore, the increased Th1 cytokine production and stronger antitumor effect were not observed in mice depleted of IFN-gamma. These data indicated that DC-tumor cell conjugates are a potent tumor vaccine. Interleukin 18 can be administrated using gene-transfected cells and enhances antitumor immunity, which is mainly mediated by IFN-gamma.     

Engineered fusion hybrid vaccine of IL-4 gene-modified myeloma and relative mature dendritic cells enhances antitumor immunity

Dendritic cell (DC)-tumor fusion hybrid vaccine which facilitates antigen presentation represents a new powerful strategy in cancer therapy. In the present study, we investigated the antitumor immunity derived from vaccination of fusion hybrids between wild-type J558 or engineered J558-IL-4 myeloma cells secreting cytokine interleukin-4 (IL-4) and immature DCs (DC(IMAT)) or relative mature DCs (DC(RMAT)). DC(RMAT) displayed an up-regulated expression of immune molecules (Ia(d), CD40, CD54, CD80 and CD86) and certain cytokines/chemokines, and enhanced ability of allogeneic T cell stimulation when compared to DC(IMAT). These DCs were fused with myeloma cells by polyethylene glycol (PEG). The fusion efficiency was approximately 20%. Our data showed that immunization of C57BL/6 mice with DC(RMAT)/J558 hybrids induced protective immunity against a high dose of J558 tumor challenge (1x10(6) cells) in 3 out of 10 immunized mice, compared with no protection seen in mice immunized with DC(IMAT)/J558 hybrids. Furthermore, immunization of mice with engineered DC(RMAT)/J558-IL-4 hybrids elicited stronger J558 tumor-specific cytotoxic T lymphocyte (CTL) responses in vitro and induced more efficient protective immunity (10/10 mice; tumor free) against J558 tumor challenge in vivo than DC(RMAT)/J558 hybrid vaccines. The results demonstrate the importance of DC maturation in DC-tumor hybrid vaccines and indicate that the engineered fusion hybrid vaccines which combine gene-modified tumor and DC vaccines may be an attractive strategy for cancer immunotherapy.     

腺病毒介导的AFP基因修饰树突状细胞的体外生物学特性

目的: 探讨腺病毒介导AFP基因修饰树突状细胞瘤苗体外生物学活性。方法:将携带小鼠AFP全长cDNA的重组腺病毒表达载体AdAFP转染BMDC，构建AFPDC肝癌瘤苗，采用电化学发光免疫测定法确证AFPDC转染的有效性，FACS检测表面分子和内吞功能，3HTdR掺入法检测T细胞增殖反应的能力，51Cr 释放法检测CTL活性。结果: AFP基因转染12 h后DC及其培养上清中可检到AFP的表达，表明腺病毒介导的AFP基因转染的有效性。AFPDC与BMDC比较B7分子明显上调，MHC分子也有轻度升高，内吞功能降低(P<0.05)。AFPDC激发同基因型小鼠T细胞增殖功能均明显高于DC对照组和LacZDC组(P<0.05)。AFPDC体外诱导CTL对Hepa16肿瘤细胞的杀伤作用具有特异性。结论: 肝癌相关基因AFP可作为抗肝癌基因治疗的切入点，该研究为肝癌树突状细胞体内免疫治疗提供了实验依据。     

Reciprocal activating interaction between 6-sulfo LacNAc+ dendritic cells and NK cells

Dendritic cells (DCs) display an extraordinary capacity to induce T‐cell responses providing the opportunity of DC‐based cancer vaccination strategies. Additional findings indicate that DCs may also play a crucial role for the activation of natural killer (NK) cells, which are important effectors in innate antitumor immunity. However, studies investigating the interaction between native human DCs and NK cells are limited. Recently, we defined 6‐sulfo LacNAc (slan) DCs as a major subpopulation of myeloid human blood DCs, which represent principal producers of the proinflammatory cytokines tumor necrosis factor‐α and interleukin (IL)‐12. Functional data revealed that slanDCs efficiently induce neoantigen‐specific CD4⁺ T cells and activate tumor‐reactive cytotoxic T cells. When evaluating the crosstalk between slanDCs and NK cells in this study, we found that lipopolysaccharide (LPS)‐activated slanDCs efficiently enhance NK cell CD69 expression and interferon (IFN)‐γ secretion. NK cell‐mediated tumor‐directed cytotoxicity was significantly improved by slanDCs. NK cell activation induced by slanDCs was critically dependent on IL‐12. When investigating the impact of NK cells on the immunostimulatory capacity of slanDCs, we observed that they promote DC maturation. In addition, NK cells strongly enhanced the secretion of immunomodulatory IL‐12 and reduced the release of immunosuppressive IL‐10 by slanDCs. IFN‐γ and cell‐to‐cell contact contributed to these effects. Furthermore, data revealed that DC‐NK cell crosstalk improves slanDC‐mediated differentiation of naïve CD4⁺ T lymphocytes into IFN‐γ‐producing Th1 cells. In conclusion, we demonstrate a reciprocal activating interaction between slanDCs and NK cells, which may play a pivotal role in the regulation of antitumor immunity. © 2008 Wiley‐Liss, Inc.     

Gamma-irradiation suppresses T-cell mediated protective immunity against a metastatic tumor in the afferent phase of the immune-response but enhances it in the efferent phase when given before immune cell transfer

Using a metastasizing animal tumor as a model we describe experimental conditions for obtaining either synergistic or antagonistic effects between host irradiation and T cell mediated antitumor immunity. The results were obtained in the well defined murine lymphoma ESb which is a spontaneous highly metastatic tumor variant expressing a tumor associated antigen that can induce protective immunity and tumor specific cytotoxic T lymphocyte (CTL) activity. Sublethal irradiation of mice during the afferent (induction) phase but not during the efferent (effector) phase of the antitumor immune response had a strong suppressive effect on protective immunity. The radiation mediated defect could be reconstituted by transfer of immune spleen cells. The immune system of syngeneic (DBA/2) and allogeneic (B10.D2) mice changed within 24 h after first contact with the ESb tumor cells from radio-sensitivity to radio-resistance possibly reflecting an active cellular response associated with the change from virgin to an antigen sensitized (primed) state of T lymphocyte differentiation. T cell depletion experiments revealed that the afferent phase was dependent on both CD4 and CD8 host T lymphocytes while the efferent phase was mainly CD8 T cell dependent. A synergistic effect between gamma-irradiation and antitumor immunity was observed in adoptive immunotherapy experiments. When tumor-bearing hosts were irradiated before intravenous transfer of either syngeneic or allogeneic antitumor immune T cells the expression of anti-metastatic protective immunity was greatly enhanced in comparison to identically treated non-irradiated hosts.