T细胞免疫在抗结核杆菌感染中的研究进展

结核分枝杆菌是引起结核病的病原体,该细菌可侵犯全身各组织器官。结核病是一种慢性传染性疾病,具有持久性特点。该细菌为胞内寄生菌,特异性免疫以细胞免疫为主,主要包括CD4+T细胞免疫和CD8+T细胞免疫。结核分枝杆菌特异性免疫应答的特点之一是感染早期T细胞免疫应答延迟。其机制与结核杆菌抑制免疫细胞(CD4+和CD8+T细胞及DC)凋亡延迟应答,通过特异性Treg细胞抑制作用延迟应答以及结核杆菌慢性感染期间存在IFN-γ信号调节网络和ESAT-6抗原的慢性刺激作用有关,以此可调节和维持免疫应答。深入了解抗原特异性T细胞特异性免疫应答的机制,有益于抗结核疫苗的研制,为临床工作提供理论依据和科学方法。     

CD4~+CD25~+调节性T细胞与肿瘤免疫研究进展

调节性T细胞(Treg)是一类具有免疫调节功能的细胞群,在机体的免疫耐受中起着关键性作用。它们主要通过细胞-细胞直接接触的方式抑制CD4+和CD8+效应性T细胞的活化和增殖,来调节获得性免疫系统,阻止自身免疫疾病的发生。Treg中以自然产生的CD4+CD25+调节性T细胞(固有Treg细胞)研究最多。在人类,调控效能主要限于CD4+CD25high亚型。由于Treg独特的生物学功能,它在自身免疫性疾病的发生、移植耐受和肿瘤的发生和转归上越来越受到重视。该文就该类细胞的特点及其与肿瘤关系的研究进展作一综述。     

以减毒沙门氏菌为SARS-CoV N DNA口服疫苗载体的初步研究

目的:以减毒沙门氏菌为载体运送SARS-CoV N DNA疫苗至小鼠体内,研究其诱导的免疫应答情况,评价减毒鼠伤寒沙门氏菌作为口服疫苗的免疫效果。方法：将含SARS-CoV N基因的pcDNA-N质粒导入减毒鼠伤寒沙门氏菌CS022中,采用口服和滴鼻相结合的方法免疫BALB/c小鼠,以ELISA检测不同时间免疫小鼠血清中抗体及其亚型;以MTT法测定特异性淋巴细胞增殖反应;ELISPOT检测细胞因子;流式检测T细胞亚型。结果：pcDNA-N DNA疫苗口服免疫后2周就可以诱生特异性IgG抗体,且以IgG2a占优势;诱导了较高水平的淋巴细胞特异性增殖反应和IFN-γ,主要以Th1免疫为主。结论：减毒沙门氏菌可以有效运送pcDNA-N重组质粒并诱导产生特异体液和细胞免疫应答,为减毒细菌作为DNA疫苗运送载体的研究提供了参考依据,也为SARS疫苗研究开辟了新方法。     

哺乳动物Toll样受体对结核分枝杆菌的控制

针对胞内菌结核分枝杆菌最为有效的免疫应答主要取决于天然免疫应答对侵入细菌的早期发现及获得性免疫应答的活化。Toll样受体在天然免疫应答发现分枝杆菌相关性分子和介导抗菌效应分子的分泌上起作用。它能调节一些免疫调节分子,这些分子能促进基于Th1细胞的T细胞发育。因此,Toll样受体的活化在抗微生物感染的机制上起一定的作用。     

结核杆菌感染T细胞介导免疫应答研究的新进展

结核病对免疫学家构成了巨大的挑战,因为它是一种慢性传染性疾病,病原体具有持久性特点.在对人和动物进行实验时,检测到结核分枝杆菌适应性免疫应答的特点之一为感染早期T细胞免疫应答延迟.新近研究揭示了此种延迟应答的机制:通过结核杆菌抑制免疫细胞(CD4+和CD8+T细胞及DC)凋亡延迟应答,通过特异性Treg细胞抑制作用延迟应答.结核杆菌慢性感染期间存在IFNγ信号调节网络和ESAT-6抗原的慢性刺激作用,抗原特异性PD-1+ CD4+T细胞具有高度增殖分化为更多终末效应性T细胞的潜能,以此可调节和维持免疫应答.深入了解抗原特异性T细胞调节与维持适应性免疫应答的机制,有益于抗结核疫苗的设计和研制.     

霍乱毒素B亚单位基因在鼠伤寒沙门氏菌中的表达

本工作成功地将霍乱毒素B亚单位(ctx B)基因插入到带有天门冬氨酸β-半醛脱氢酶基困(asd+)的pYAZ48质粒中,并将它转化至天门冬氨酸β-半醛脱氢酶突变(asd-)鼠伤寒沙门氏菌中。实验结果表明,ctx B亚单位基因能在鼠伤寒沙门氏菌中高效表达,并且表达的蛋白能分泌到细胞外。动物实验结果也表明：该疫苗菌株能在肠粘膜细胞定居;口服及全身免疫均能产生较高的抗体,并能增强动物细胞的免疫功能;对伤寒、霍乱有毒株的攻击有良好的保护效果。该系统的应用为疫苗基因工程提供了一个新的途径。     

鼠伤寒沙门氏菌Ⅲ型分泌系统抗感染类抑制剂的筛选

【背景】肠道沙门氏菌(Salmonella enterica)是一种常见的食源性肠道致病菌,可以感染人畜并引发食物中毒、伤寒等疾病。近年来因抗生素滥用导致肠道沙门氏菌耐药性问题日益严峻,迫切需要开发新型抗感染药物。肠道沙门氏菌致病的关键在于与宿主细胞接触后可以通过Ⅲ型分泌系统(type Ⅲ secretion system, T3SS)向宿主细胞内注射效应蛋白,进而调控宿主细胞囊泡运输和免疫应答等生理活动,以方便其高效侵染宿主细胞。T3SS是一类由超过20种蛋白质组成、高度复杂的跨膜分子机器,是革兰氏阴性病原菌中普遍存在的一类蛋白质运输系统和毒力系统。在不同病原菌中,其结构与功能非常保守。位于T3SS核心跨膜区的SctV家族蛋白是T3SS中最保守的组分之一,参与T3SS能量供应和效应蛋白的分泌过程,SctV蛋白的关键氨基酸突变失活后会导致鼠伤寒沙门氏菌丧失对宿主的入侵能力。【目的】以沙门氏菌SctV家族蛋白为靶点,尝试通过虚拟筛选技术筛选与SctV胞内区相互作用的抗感染类T3SS抑制剂。【方法】结合体外相互作用分析、细菌生长曲线实验、细菌分泌实验和细胞侵染实验等对候选分子进行抑制效果的...     

OX40参与RSV气道炎症反应中CD4~+T细胞的增殖活化

OX40是TNFR超家族成员之一,主要表达于活化的CD4~+T细胞表面。OX40能促进CD4~+T细胞的增殖与活化,但其在呼吸道合胞病毒(respiratorysyncytial virus, RSV)感染所诱发的气道炎症反应中对CD4~+T细胞增殖与活化的作用尚不十分清楚。通过建立RSV急性感染的实验动物模型,采用流式细胞术、免疫磁珠分选、Real-time RT-PCR、Elisa、Western Blot等实验方法,旨在揭示在RSV感染性气道炎症中OX40对CD4~+T细胞增殖与活化的影响作用。结果显示,RSV感染后脾组织内表达OX40的CD4~+T细胞数量及CD4~+T细胞OX40 mRNAs和OX40蛋白表达水平显著增加。从感染3 d的BALB/c鼠脾组织分选CD4~+T细胞进行体外培养并加入OX40激动型抗体,发现加入OX40激动型抗体的CD4~+T细胞组与未加组相比,其细胞因子IL-2、IFN-γ和IL-13的表达水平显著增高。证实在感染性气道炎症中OX40对CD4~+T的细胞增殖与活化起着重要的调控作用。     

与CD95相关的细胞凋亡和免疫调节

细胞凋亡是一个十分复杂的过程,就目前研究结果来看,CD95系统的调控起到了很重要的作用。它与免疫杀伤、肿瘤免疫和自身免疫疾病密切相关。CD95系统不仅能够维持免疫系统的自身稳定,同时也能发挥免疫反应的作用。在特异性的细胞毒效应作用中,CD95通路是细胞毒性T淋巴细胞（CTL）杀伤靶细胞的一种方式;CD95通路在肿瘤中的失效使之逃避免疫监视和削弱免疫反应;活化的T细胞和B细胞增殖后所出现的细胞凋亡,主要是通过CD95／CD95L诱导的凋亡途径产生。一旦CD95－CD95L体系功能紊乱,就会造成严重的自身免疫疾病。     

T细胞免疫在抗结核杆菌感染中的研究进展

结核分枝杆菌是引起结核病的病原体,该细菌可侵犯全身各组织器官。结核病是一种慢性传染性疾病,具有持久性特点。该细菌为胞内寄生菌,特异性免疫以细胞免疫为主,主要包括CD4＋T细胞免疫和CD8＋T细胞免疫。结核分枝杆菌特异性免疫应答的特点之一是感染早期T细胞免疫应答延迟。其机制与结核杆菌抑制免疫细胞（CD4＋和CD8＋T细胞及DC）凋亡延迟应答,通过特异性Treg细胞抑制作用延迟应答以及结核杆菌慢性感染期间存在IFN-γ信号调节网络和ESAT-6抗原的慢性刺激作用有关,以此可调节和维持免疫应答。深入了解抗原特异性T细胞特异性免疫应答的机制,有益于抗结核疫苗的研制,为临床工作提供理论依据和科学方法。     

Dual role of B cells in mediating innate and acquired immunity to herpes simplex virus infections

mu-immunoglobulin chain gene targeted B-cell-deficient mice of susceptible BALB/c strain and resistant C57B1/6 strain are up to 100- to 1000-fold more susceptible to cutaneous infection by herpes simplex virus (HSV) than the respective control wild type mice. The effect of the lack of B cells on immunity to HSV infections was analyzed and B cells were found to play a dual role in affecting both innate and acquired immune responses. Natural antibodies (IgM isotype), reactive with HSV have an anti-viral effect in the innate control of primary cutaneous HSV infection. B cells can also function as antigen-presenting cells for the stimulation of HSV-specific CD4+ T-cell responses. Consequently, CD4+ T cells and interferon-gamma responses were found to be significantly impaired in HSV-infected B-cell-deficient mice compared to that seen in control mice. No significant differences were found in natural-killer-cell- or HSV-specific CD8+ T-cell activity between control and B-cell-deficient mice. Our results imply a role for B cell in mediating innate and CD4+ T-cell-specific immunity in determining susceptibility to primary HSV infections.     

Inefficient presentation of tumor-derived antigen by tumor-infiltrating dendritic cells

BACKGROUND: Transplantable B16 melanoma is widely used as a tumor model to investigate tumor immunity. We wished to characterize the leukocyte populations infiltrating B16 melanoma tumors, and the functional properties of tumor-infiltrating dendritic cells (TIDC). MATERIALS AND METHODS: We used the B16 melanoma cell line expressing ovalbumin protein (OVA) to investigate the phenotype and T cell stimulatory capacity of TIDC. RESULTS: The majority of leukocytes in B16 melanoma were macrophages, which colocalized with TIDCs, B and T cells to the peripheral area of the tumor. Both myeloid and plasmacytoid DC populations were present within tumors. Most of these DCs appeared immature, but about a third expressed a mature phenotype. TIDCs did not present tumor-derived antigen, as they were unable to induce the proliferation of tumor-specific CD4+ and CD8+ T cells in vitro unless in the presence of specific peptides. Some presentation of tumor-derived antigen could be demonstrated in the tumor-draining lymph node using in vivo proliferation assays. However, while proliferation of CD8+ T cells was reproducibly demonstrated, no proliferation of CD4+ T cells was observed. CONCLUSION: In summary, our data suggest that DCs in tumors have limited antigen-presenting function. Inefficient antigen presentation extends to the tumor-draining lymph node, and may affect the generation of antitumor immune responses.     

Commensal-induced regulatory T cells mediate protection against pathogen-stimulated NF-kappaB activation

Host defence against infection requires a range of innate and adaptive immune responses that may lead to tissue damage. Such immune-mediated pathologies can be controlled with appropriate T regulatory (Treg) activity. The aim of the present study was to determine the influence of gut microbiota composition on Treg cellular activity and NF-kappaB activation associated with infection. Mice consumed the commensal microbe Bifidobacterium infantis 35624 followed by infection with Salmonella typhimurium or injection with LPS. In vivo NF-kappaB activation was quantified using biophotonic imaging. CD4+CD25+Foxp3+ T cell phenotypes and cytokine levels were assessed using flow cytometry while CD4+ T cells were isolated using magnetic beads for adoptive transfer to na?ve animals. In vivo imaging revealed profound inhibition of infection and LPS induced NF-kappaB activity that preceded a reduction in S. typhimurium numbers and murine sickness behaviour scores in B. infantis-fed mice. In addition, pro-inflammatory cytokine secretion, T cell proliferation, and dendritic cell co-stimulatory molecule expression were significantly reduced. In contrast, CD4+CD25+Foxp3+ T cell numbers were significantly increased in the mucosa and spleen of mice fed B. infantis. Adoptive transfer of CD4+CD25+ T cells transferred the NF-kappaB inhibitory activity. Consumption of a single commensal micro-organism drives the generation and function of Treg cells which control excessive NF-kappaB activation in vivo. These cellular interactions provide the basis for a more complete understanding of the commensal-host-pathogen trilogue that contribute to host homeostatic mechanisms underpinning protection against aberrant activation of the innate immune system in response to a translocating pathogen or systemic LPS.     

NK cells stimulate proliferation of T and NK cells through 2B4/CD48 interactions

Few studies have addressed the consequences of physical interactions between NK and T cells, as well as physical interactions among NK cells themselves. We show in this study that NK cells can enhance T cell activation and proliferation in response to CD3 cross-linking and specific Ag through interactions between 2B4 (CD244) on NK cells and CD48 on T cells. Furthermore, 2B4/CD48 interactions between NK cells also enhanced proliferation of NK cells in response to IL-2. Overall, these results suggest that NK cells augment the proliferation of neighboring T and NK cells through direct cell-cell contact. These results provide new insights into NK cell-mediated control of innate and adaptive immunity and demonstrate that receptor/ligand-specific cross talk between lymphocytes may occur in settings other than T-B cell or T-T cell interactions.     

Innate imprinting by the modified heat-labile toxin of Escherichia coli (LTK63) provides generic protection against lung infectious disease

In a healthy individual, the lung contains few lymphoid cells. However, amplified immune responses, as exemplified during lung infection, can cause extensive tissue damage. We have previously demonstrated that one lung infection modulates the immunopathological outcome to a subsequent unrelated pathogen. Mimicking heterologous immunity may provide a means of enhancing both innate and acquired immunity. We now show that prior lung administration of a modified heat-labile toxin from Escherichia coli (LTK63) enhances immunity to respiratory syncytial virus, influenza virus, and the fungus Cryptococcus neoformans. Treatment with LTK63 decreased lung inflammation and tissue damage and improved the ability to resolve the infection. APCs expressing the activation markers MHC class II, CD80, and CD40 increased in number in the lung. LTK63 treatment increased the pathogen-specific IgA response in the nasal mucosa and simultaneously decreased inflammatory cytokine production (IFN-gamma and TNF-alpha) after infection. The number of activated CD8(+)CD44(+) T cells and the respiratory syncytial virus- or influenza-specific CD8-proliferative responses increased, although the total inflammatory infiltrate was reduced. LTK63 treatment matured lung APCs (LTK63 prevented efficient presentation of whole OVA to DO11.10 cells, whereas OVA peptide presentation was unaffected), enhanced immunity in both a Th1 and Th2 environment, was long lasting, and was not pathogen or host strain specific; the protective effects were partially independent of T and B cells. Innate imprinting by toxin-based immunotherapeutics may provide generic protection against infectious disease in the lung, without the need for coadministered pathogen-specific Ag.     

TLR agonists abrogate costimulation blockade-induced prolongation of skin allografts

Costimulation blockade protocols are effective in prolonging allograft survival in animal models and are entering clinical trials, but how environmental perturbants affect graft survival remains largely unstudied. We used a costimulation blockade protocol consisting of a donor-specific transfusion and anti-CD154 mAb to address this question. We observed that lymphocytic choriomeningitis virus infection at the time of donor-specific transfusion and anti-CD154 mAb shortens allograft survival. Lymphocytic choriomeningitis virus 1) activates innate immunity, 2) induces allo-cross-reactive T cells, and 3) generates virus-specific responses, all of which may adversely affect allograft survival. To investigate the role of innate immunity, mice given costimulation blockade and skin allografts were coinjected with TLR2 (Pam3Cys), TLR3 (polyinosinic:polycytidylic acid), TLR4 (LPS), or TLR9 (CpG) agonists. Costimulation blockade prolonged skin allograft survival that was shortened after coinjection by TLR agonists. To investigate underlying mechanisms, we used "synchimeric" mice which circulate trace populations of anti-H2b transgenic alloreactive CD8+ T cells. In synchimeric mice treated with costimulation blockade, coadministration of all four TLR agonists prevented deletion of alloreactive CD8+ T cells and shortened skin allograft survival. These alloreactive CD8+ T cells 1) expressed the proliferation marker Ki-67, 2) up-regulated CD44, and 3) failed to undergo apoptosis. B6.TNFR2-/- and B6.IL-12R-/- mice treated with costimulation blockade plus LPS also exhibited short skin allograft survival whereas similarly treated B6.CD8alpha-/- and TLR4-/- mice exhibited prolonged allograft survival. We conclude that TLR signaling abrogates the effects of costimulation blockade by preventing alloreactive CD8+ T cell apoptosis through a mechanism not dependent on TNFR2 or IL-12R signaling.     

Novel exosome-targeted CD4+ T cell vaccine counteracting CD4+25+ regulatory T cell-mediated immune suppression and stimulating efficient central memory CD8+ CTL responses

T cell-to-T cell Ag presentation is increasingly attracting attention. In this study, we demonstrated that active CD4+ T (aT) cells with uptake of OVA-pulsed dendritic cell-derived exosome (EXO(OVA)) express exosomal peptide/MHC class I and costimulatory molecules. These EXO(OVA)-uptaken (targeted) CD4+ aT cells can stimulate CD8+ T cell proliferation and differentiation into central memory CD8+ CTLs and induce more efficient in vivo antitumor immunity and long-term CD8+ T cell memory responses than OVA-pulsed dendritic cells. They can also counteract CD4+25+ regulatory T cell-mediated suppression of in vitro CD8+ T cell proliferation and in vivo CD8+ CTL responses and antitumor immunity. We further elucidate that the EXO(OVA)-uptaken (targeted)CD4+ aT cell's stimulatory effect is mediated via its IL-2 secretion and acquired exosomal CD80 costimulation and is specifically delivered to CD8+ T cells in vivo via acquired exosomal peptide/MHC class I complexes. Therefore, EXO-targeted active CD4+ T cell vaccine may represent a novel and highly effective vaccine strategy for inducing immune responses against not only tumors, but also other infectious diseases.     

Direct stimulation of T cells by type I IFN enhances the CD8+ T cell response during cross-priming

Type I IFN (IFN-alphabeta), which is produced rapidly in response to infection, plays a key role in innate immunity and also acts as a stimulus for the adaptive immune response. We have investigated how IFN-alphabeta induces cross-priming, comparing CD8+ T cell responses generated against soluble protein Ags in the presence or absence of IFN-alphabeta. Injection of IFN-alpha was found to prolong the proliferation and expansion of Ag-specific CD8+ T cells, which was associated with marked up-regulation of IL-2 and IL-15 receptors on Ag-specific cells and expression of IL-15 in the draining lymph node. Surprisingly, neither IL-2 nor IL-15 was required for IFN-alpha-induced cross-priming. Conversely, expression of the IFN-alphabetaR by T cells was shown to be necessary for effective stimulation of the response by IFN-alpha. The finding that T cells represent direct targets of IFN-alphabeta-mediated stimulation reveals an additional mechanism by which the innate response to infection promotes adaptive immunity.