CD4~+T 细胞与肿瘤免疫

CD4~+T细胞不仅辅助激活CD8~+T细胞,而且对记忆性细胞毒性T淋巴细胞(CTL)应答的产生和维持起重要作用,并具有直接的抗肿瘤功能.另外,CD4~+CD25~+ 调节性T细胞(Tregs)具有免疫负调控功能,在肿瘤免疫抑制及免疫逃逸中发挥重要作用,是肿瘤免疫治疗失败的重要原因.近年肿瘤免疫治疗已获得很大进步,相关肿瘤疫苗的研究也备受关注.     

CD4+ T lymphocytes: a critical component of antitumor immunity

Both prophylactic and therapeutic vaccines targeting a wide variety of cancers are being developed. Because of the potency of cell-mediated immunity, many vaccine strategies are focused on activating tumor-specific cytotoxic CD8⁺ T lymphocytes. CD4⁺ T lymphocytes are a key element in optimal activation of CD8⁺ T cells and in the maintenance of immune memory, and therefore their activation is critical for cancer vaccine efficacy. This article reviews the mechanisms by which CD4⁺ T cells facilitate tumor immunity and the vaccine strategies that enhance CD4⁺ T cell activity.     

CD4+T细胞与肿瘤免疫

在肿瘤免疫中细胞免疫发挥着重要作用,其中T细胞介导的特异性免疫应答反应更为重要.近年来CD4+T细胞在抗肿瘤免疫中的作用越来越受到重视.在肿瘤免疫中CD4+T细胞启动后可以通过多种机制启动细胞毒性T淋巴细胞(CTL),维持和加强CTL的抗肿瘤反应,并且可以作为效应细胞发挥抗肿瘤作用,CD4+T细胞中的一个亚群细胞CD4+ CD25+T调节细胞对肿瘤免疫有抑制作用.     

CD4+T细胞与肿瘤免疫

在肿瘤免疫中细胞免疫发挥着重要作用,其中T细胞介导的特异性免疫应答反应更为重要.近年来CD4+T细胞在抗肿瘤免疫中的作用越来越受到重视.在肿瘤免疫中CD4+T细胞启动后可以通过多种机制启动细胞毒性T淋巴细胞(CTL),维持和加强CTL的抗肿瘤反应,并且可以作为效应细胞发挥抗肿瘤作用,CD4+T细胞中的一个亚群细胞CD4+ CD25+T调节细胞对肿瘤免疫有抑制作用.     

Cytotoxic T lymphocytes from HLA-A2.1 transgenic mice define a potential human epitope from simian virus 40 large T antigen

Recent reports have documented the presence of SV40 large T antigen (T ag) sequences in a number of human tumors and raised the question of whether cellular immunity to T ag is elicited in such individuals. We used HLA-A2.1 transgenic C57BL/6 mice to identify an epitope from T ag recognized by CD8+ CTLs when presented by this human MHC class I molecule. Immunization of HLA-A2.1 transgenic mice with syngeneic T ag-transformed cells resulted in the induction of HLA-A2.1-restricted, T ag-specific CTLs. The target epitope, residues 281-289 (KCDDVLLLL) of T ag, was identified using both cell lines expressing T ag variants and synthetic T ag peptides. Peptide 281-289 bound stably to HLA-A2.1 molecules, effectively sensitized target cells for CTL lysis, and was efficiently processed from endogenous T ag in cells of both mouse and human origin. CTLs were not cross-reactive on the human BK or JC virus T ags. Thus, SV40 T ag 281-289 represents a potential specific CTL recognition epitope for humans.     

Enhanced expression of vascular endothelial growth factor (VEGF) plays a critical role in the tumor progression potential induced by simian virus 40 large T antigen

Vascular endothelial growth factor (VEGF), an important angiogenic factor, regulates cell proliferation, differentiation, and apoptosis through activation of its tyrosine-kinase receptors, such as Flt-1 and Flk-1/Kdr. Human malignant mesothelioma cells (HMC), which have wild-type p53, express VEGF and exhibit cell growth increased by VEGF. Here, we demonstrate that early transforming proteins of simian virus (SV) 40, large tumor antigen (Tag) and small tumor antigen (tag), which have been associated with mesotheliomas, enhanced HMC proliferation by inducing VEGF expression. SV40-Tag expression potently increased VEGF protein and mRNA levels in several HMC lines. This effect was suppressed by the protein synthesis inhibitor, cycloheximide. Inactivation of the VEGF signal transduction pathway by expression of soluble form of Flt-1 inhibited Flk-1/Kdr activation and HMC proliferation induced by SV40 early genes. Experiments with SV40 mutants revealed that SV40-Tag, but not -tag, is involved in the VEGF promoter activation. However, concomitant expression of SV40-tag enhanced Tag function. In addition, SV40-Tag expression sustained VEGF induction in colon carcinoma cell line (CCL)-233, which have wild-type p53, but not in CCL-238, which lack functional p53. These data indicate that VEGF regulation by SV40 transforming proteins can represent a key event in SV40 signaling relevant for tumor progression.     

CD+4CD+25调节性T细胞与肿瘤免疫

 近期研究发现一个有独特免疫调节功能的T细胞亚群：CD+4 CD+25调节性T细胞,不仅能抑制自身免疫性疾病发生,还参与肿瘤免疫的调节。这群细胞具有免疫无能和免疫抑制特性,与肿瘤免疫逃逸有密切的关系。肿瘤环境中CD+4 CD+25调节性T细胞增加,导致肿瘤免疫失调,去除这群细胞可有效诱导肿瘤免疫,为肿瘤治疗提供了一种新的思路。     

Detection of simian virus 40 surface-associated large tumor antigen by enzyme-catalyzed radioiodination

To facilitate detection of SV40 surface-associated tumor antigen (T-ag), conditions were established to surface label T-ag on intact cells by lactoperoxidase-catalyzed radioiodination (¹²⁵I/LPO). SDS-PAGE analysis of anti-T immunoprecipitates of SV40-transformed and -infected cells labelled with ¹²⁵I/LPO revealed the presence of iodinated T-ag. Several types of control experiments were employed to guarantee the surface specificity of the ¹²⁵I/LPO labelling technique. When SV40-transformed mouse cells were surface labelled with lactoperoxidase and glucose oxidase immobilized on insoluble beads, a preparation less readily internalized than soluble enzymes, T-ag was iodinated. Selective immunoprecipitation of surface antigens demonstrated that lactoperoxidase did not iodinate internally localized T-ag. A reconstruction experiment in which an extract of SV40-infected cells was added to uninfected cells prior to surface labelling suggested that T-ag released from lysed cells did not adhere significantly to monolayer surfaces and become iodinated. Finally, systematic omission of reactants from the iodination reaction revealed that exogenous addition of lactoperoxidase and H₂O₂ was necessary to generate an iodinated T-ag, indicating that endogenous host cell reactants do not contribute significantly to the iodination of T-ag. ¹²⁵I-labelled T-ag was detectable on the surface of SV40 tsA-infected cells at the nonpermissive temperature 24 h post infection, indicating that the tsA lesion does not prevent the interaction of T-ag with the cell surface. When ¹²⁵I/LPO-labelled transformed or infected cells were chased for 2.5 h after labelling, iodinated T-ag was no longer associated with the cell monolayer but was immunoprecipitable from culture supernatants. Cultures from which labelled T-ag had been shed could then be relabelled with ¹²⁵I/LPO and surface-associated T-ag was again detectable. These data suggest that surface-associated T-ag is continuously shed from the cell surface and is rapidly replaced in the membrane by intracellular T-ag.     

A new anti-p53 monoclonal antibody, previously reported to be directed against the large T antigen of simian virus 40

The PAb1620 antibody belongs to a group of monoclonal antibodies reported to recognize nuclear large T antigen of simian virus 40 (SV40). In the case of PAb1620 there was some indication that the antibody reacted preferentially with large T when it was complexed with p53, the cellular transformation-related antigen. However, we found that PAb1620 does not appear to react with SV40 large T, either free or in complex with p53. In this paper we demonstrate that PAb1620 is, in fact, directed against the p53 protein and recognizes a conformation-dependent epitope. In addition, PAb1620 recognises human p53 from SV80 cells.     

CD4+CD25+调节性T细胞与抗肿瘤免疫

CD4^＋CD25^＋调节性T（CD4^＋CD25^＋Tr）细胞是一类维持机体自身耐受的T细胞亚群,分布广泛,但不同组织表型有所不同。它们可由胸腺自然产生,也可在外周血中诱导产生,其活化要依赖于特异性抗原的存在。CD4^＋CD25^＋Tr细胞发挥抑制效应是通过细胞接触依赖或分泌细胞因子这两种方式。去除CD4^＋CD25^＋Tr细胞或抑制其功能,重新募集效应性T细胞能够增强机体抗肿瘤作用,这将成为一种可行的肿瘤免疫治疗方法。     

Infrequent existence of simian virus 40 large T antigen DNA in malignant mesothelioma in Japan

Malignant mesothelioma is the most common primary pleural neoplasm. Association of simian virus 40 (SV40) with malignant mesothelioma has been reported, suggesting that SV40 plays an important role in the origin of a subset of these tumors. However, significant geographic variation is present as to how often this association occurs. As no study concerning SV40 in malignant mesothelioma has been reported from Japan, we examined the frequency of SV40 infection in Japanese malignant mesothelioma cases. In pleural malignant mesothelioma tissue from 35 patients in Japan, we sought the presence of SV40 large T antigen DNA using real-time polymerase chain reaction (PCR), as well as expression of the viral protein using immunohistological methods. Real-time PCR demonstrated that two of 35 mesotheliomas contained DNA sequences encoding portions of SV40 large T antigen. None of the 35 malignant mesothelioma specimens showed immunoreactivity for SV40 large T antigen. SV40 infection does not appear to have a major role in the development of malignant mesothelioma in Japan.     

Sequential loss of cytotoxic T lymphocyte responses to simian virus 40 large T antigen epitopes in T antigen transgenic mice developing osteosarcomas

The role of CTL tolerance in tumor immunity to SV40 large T antigen (T ag)-induced tumors was studied using T ag transgenic mice of the line 501 (H2b). 501 mice express SV40 T ag under the influence of the alpha-amylase promoter, which leads to the development of osteogenic osteosarcomas late in life and eventual death between 12 and 17 months of age. We determined the ability of 501 mice to respond to the four H2b-restricted T ag CTL epitopes, which include epitope I (T ag 206-215), epitope II/III (T ag 223-231), the immunorecessive epitope V (T ag 489-497), restricted by H2-Db, and epitope IV (T ag 404-411), restricted by H2-Kb. We demonstrate that 501 mice are partially tolerant to the H2b-restricted T ag epitopes. Immunization of 4-month-old 501 mice with T ag-transformed syngeneic cell lines or a recombinant vaccinia virus expressing full-length T ag elicited CTL responses against the H2-Kb-restricted T ag epitope IV only. In contrast, immunization of 4-month-old 501 mice with recombinant vaccinia viruses expressing individual T ag epitopes as minigenes elicited CTLs against epitopes I, IV, and V, but not against epitope II/III. Complete tolerance to epitopes I, IV, and V developed in 501 mice, but the age when tolerance was detected varied for each epitope. Tolerance to epitope I occurred by 6 months of age and was accelerated in the absence of CD4+ T cells. Tolerance to the immunorecessive epitope V was observed in 12-month-old 501 mice but was independent of the presence of osteosarcomas. In contrast, CTLs specific for epitope IV were detected in mice from 3 to 14 months of age but not in mice that had developed osteosarcomas. Analysis of epitope IV-specific CD8+ cells derived from 3-month-old 501 mice with H2-Kb/epitope IV tetramers revealed decreased numbers of epitope IV-specific CD8+ cells in 501 mice relative to C57BL/6 mice, with a further decrease in older 501 mice. Tumor progression resulted in loss of H2-Kb/epitope IV tetramer staining CD8+ cells. Thus, progression to tolerance to individual T ag CTL epitopes in 501 mice is epitope dependent.     

Naturally occurring cell-mediated cytotoxicity against simian virus 40-transformed 3T3 murine tumor cells

The tumorigenicity and host protective mechanisms induced by simian virus 40 (SV40)-transformed 3T3 cells (SV403T3) were evaluated in syngeneic BALB/c mice. Tumors were regularly produced by sc inoculation of SV403T3 cells; the incidence, latent period, and survival were proportional to the size of the initial inoculum. With the use of an in vitro 18-hour 51Cr cytotoxicity assay, spleen cells from normal mice showed a dose-related killing activity against the SV403T3 cells. At an effector cell-to-target cell ratio of 200:1, the average lysis was 56 +/- 6%. This reaction appeared specific for the virally transformed targets; the mean lysis of parent 3T3 cells was 23 +/- 5%. Effectors were resistant to anti-theta serum and not removed by adherence to plastic or nylon wool. Tissue distribution studies indicated that these effectors were present in high concentrations in spleen, bone marrow, lymph nodes, and peritoneal cavity. Low levels of activity were associated with cells from the thymus. In the present studies specific T-cell cytotoxicity against the SV403T3 cells could not be demonstrated. Animals challenged with nonviable SV403T3 cells prior to tumor cell inoculation did not show increased in vivo resistance. In parallel, the in vitro cytotoxicity of animals inoculated with SV403T3 tumor cells showed no heightened cell killing compared to the cytotoxicity of normal controls.     

肝癌微环境中CD4~+CD25~+调节性T细胞与T细胞免疫的关系

目的:探讨肝细胞癌组织中CD4 CD25 调节性T细胞(CD4 CD25 regulartory Tcell,Treg)与肿瘤微环境T细胞免疫的关系。方法:对52例肝细胞癌组织和癌旁组织用CD4、CD25双重酶标免疫组化染色和用CD8 EnVision法染色,对癌组织中Treg细胞和CD4 T、CD8 T、CD4 T/CD8 T比值进行相关性分析。结果:正常肝脏组织中未发现Treg细胞,肝癌和癌旁组织中Treg细胞单个高倍视野平均数分别为(7.6±2.84)、(5.2±1.67),两组比较有显著差异(P<0.01);肝癌及癌旁组织中CD4 T细胞单个高倍视野平均数分别为(18.2±3.57)、(25.9±3.36),两组比较有显著差异(P<0.01);肝癌及癌旁组织中CD8 T细胞单个高倍视野平均数分别为(49.9±6.61)、(49.5±6.43),两组比较无明显差异;肝癌及癌旁组织中CD4 T/CD8 T比值分别为(0.37±0.08)、(0.53±0.09),两组比较有显著差异(P<0.01);肝癌组织中Treg细胞的数量与其浸润性CD4 T淋巴细胞的数量及CD4 T/CD8 T比值呈显著负相关(P<0.01),而与浸润性CD8 T淋巴细胞的数量分布无明显相关性。结论∶Treg细胞在肝癌微环境中可能通过抑制CD4 T淋巴细胞的增殖来抑制肿瘤局部免疫。     

Human kin17 protein directly interacts with the simian virus 40 large T antigen and inhibits DNA replication

Kin17 is an evolutionarily conserved DNA-binding protein, which forms intranuclear foci in proliferating cells. Recent data have suggested that human kin17 protein is associated with cell proliferation and unrepaired DNA lesions. Herein, we show that human fibroblasts (MRC5-V2 and CHSV4) immortalized with SV40 overexpress endogenous kin17 protein, as compared with normal diploid human fibroblasts. We observed that certain carcinoma cell lines also up-regulated kin17 protein, suggesting that increased kin17 protein levels may be a consequence of the immortalized phenotype. We report here that the endogenous kin17 protein is located in nucleoplasmic foci and colocalizes with SV40 large T antigen. Purification of human kin17 protein allowed analysis of the physical interaction with T antigen by several in vitro and in vivo assays. Large T antigen and human kin17 protein are part of the same high molecular weight multiprotein complex in human cells. Furthermore, human kin17 protein interacts with T antigen bound to the SV40 DNA origin of replication. Strikingly, the overexpression of human kin17 protein in vivo and the introduction of increased amounts of human kin17 protein in an in vitro assay reduced T-antigen-dependent DNA replication, suggesting that kin17 protein may be involved in the DNA replication process in human cells.     

Specific simian virus 40 (SV40)-induced immunity against transplantable SV40 tumor in Syrian hamsters: abrogation by BCG vaccination.

Syrian hamsters were immunized with simian virus 40 (SV40) and/or BCG (in different time and sequence combinations) and were subsequently challenged with SV40-induced transplantable tumor cells. Immunization of hamsters with some but not all BCG preparations alone induced high levels of resistance to SV40 transplantable tumor cells. The immunization with SV40 of hamsters preliminarily inoculated with BCG induced antitumor immunity, the level of which was equal to resistance induced by immunization of normal animals with SV40. No cumulative effects of BCG and SV40 immunizations were noticed in any of our experiments even when BCG prepartions alone induced considerable increase of antitumor resistance. Inoculation of animals with the mixture of SV40 and BCG was generally less effective than that with SV40 alone. Inoculation of BCG preparations into hamsters preimmunized with SV40 resulted in the complete or partial abrogation of the resistance induced by SV40. All preparations of BCG, independent from their antitumor activity per se, decreased the resistance induced by SV40. The effect of this BCG-induced abrogation of resistance was observed in animals immunized with SV40 7-427 days before inoculation of BCG. The effect was not short-term, as it was still observed 3 months after BCG inoculation.     

CD4~+CD25~+调节性T细胞与抗肿瘤免疫

CD4~+CD25~+调节性T(CD4~+CD25~+Tr)细胞是一类维持机体自身耐受的T细胞亚群,分布广泛,但不同组织表型有所不同。它们可由胸腺自然产生,也可在外周血中诱导产生,其活化要依赖于特异性抗原的存在。CD4~+CD25~+Tr细胞发挥抑制效应是通过细胞接触依赖或分泌细胞因子这两种方式。去除CD4~+CD25~+Tr细胞或抑制其功能,重新募集效应性T细胞能够增强机体抗肿瘤作用,这将成为一种可行的肿瘤免疫治疗方法。     

CD4+ T cells play a crucial role for lenalidomide in vivo anti-tumor activity in murine multiple myeloma

Lenalidomide modulates the host immune response against myeloma via multiple actions. Although these effects have been elucidated in vitro, the central action of lenalidomide-mediated anti-myeloma immune response in vivo is not clear. To investigate its immune action in vivo, we selected the murine myeloma cell line 5TGM1, which is resistant to direct tumoricidal effects of lenalidomide in vitro and in immunodeficient mice, but sensitive to lenalidomide treatment in 5TGM1-bearing immunocompetent mice. Depletion of CD4⁺ T cells, but not NK cells, B cells, or CD8⁺ T cells, deprived lenalidomide of its therapeutic effects on 5TGM1-bearing immunocompetent mice. Lenalidomide significantly increased the numbers of IFN-γ-secreting CD4⁺ and CD8⁺ T cells but had no effects on NK cells and B cells in this mouse model. Lenalidomide slightly decreased the number of CD25⁺Foxp3⁺ T cells but increased perforin expression in CD8⁺ T cells in vivo. Using this mouse model for investigation of anti-tumor immune action of lenalidomide, we demonstrated that lenalidomide facilitated a type-1 anti-tumor immune response in vivo. The CD4⁺ T cell subset may play a critical role in the lenalidomide-mediated anti-myeloma immune response in vivo.     

CD4+T细胞在肝细胞癌中的作用

CD4+T细胞为一系列多功能细胞,研究发现肝细胞癌(HCC)中大部分CD4+T细胞亚群可通过活化或抑制机体固有免疫细胞、适应性免疫细胞及非免疫细胞等,参与肿瘤血管生成及浸润、肿瘤细胞凋亡、急性期蛋白及促癌基因的表达,进而发挥肿瘤促进或抑制作用.     

CD4+ T-cell help in the tumor milieu is required for recruitment and cytolytic function of CD8+ T lymphocytes

CD4 help for CD8(+) T lymphocytes prevents tolerance and promotes the survival of effector and memory CD8(+) T cells. Here, we describe additional helper functions that require CD4(+) T cells within the tumor environment. CD8(+) T-cell recruitment, proliferation, and effector function within the tumor were greatly enhanced by tumor-specific CD4(+) T cells. Recruitment of CD8(+) T cells was accelerated by IFN-γ-dependent production of chemokines. Production of interleukin-2 by tumor resident CD4(+) T cells enhanced CD8(+) T-cell proliferation and upregulated expression of granzyme B. These results highlight a novel role for tumor-specific CD4(+) T cells in promoting CD8(+) T-cell recruitment and cytolytic function, two previously unappreciated aspects of tumor-specific CD4 help.