CD28分子的研究进展

目前大量实验已证明,CD28家族分子与B7家族分子结合后产生的共刺激信号,即第二信号在免疫应答的T细胞激活中起重要作用.CD28与B7两种分子的相互作用可产生一个特殊的协同刺激使TCR介导的抗原识别信号导致细胞的活化而不是无能,现就CD28家族分子的结构、配体、信号传导以及对免疫应答的调控作一综述.     

PD-L2/CTLA-4融合蛋白的表达,纯化及初步功能鉴定

细胞毒性T细胞相关抗原(Cytotoxic T Lymphocyte Associated Antigen 4,CTLA-4)是体内重要的免疫负调控因子,它可与CD28竞争跟B7分子的结合,抑制T细胞的活化.程序性死亡蛋白配体2(Programmed Death Ligand-2,PD-L2)可以和其受体程序性死亡因子1(Programmed Death 1,PD-1)结合,产生的信号可以抑制TCR(T Cell Receptor)介导的T细胞增殖和细胞因子产生.为了得到一种新型的高效免疫负调控蛋白,从人基因组中克隆了CTLA-4和PD-L2胞外区,并在大肠杆菌中实现了其融合表达和纯化.ConA转化实验表明,PD-L2/CTLA-4融合蛋白能显著抑制小鼠淋巴细胞增殖,抑制率达69%.相比于CTLA-4和PD-L2分子单独使用,抑制率分别提高了23%和10%,混合淋巴实验抑制率达71%,提示其具有免疫负调控功能.     

共刺激分子B7和CD40对日本血吸虫感染小鼠Th1/Th2免疫偏移的调控作用

为观察干预B7/CD28和CD40/CD40L共刺激信号对Th1/Th2细胞因子表达水平和Th1/Th 2免疫偏移的调控作用, 分别取小鼠感染日本血吸虫后6、8、10和12周的脾淋巴细胞经抗CD8 0(B7-1)mAb、抗CD86(B7-2)mAb、抗CD40mAb和抗CD40LmAb处理后培养72h,用ELISA 双抗体夹心法测定培养上清中IFN-γ和IL-4的表达水平的动态变化并分析干预2种不同的共刺激信号对 Th1/Th2免疫偏移的影响.结果显示抗CD80mAb和抗CD86mAb均能显著抑制IL-4的表达水平, 尤其是抗CD86mAb对IL-4抑制作用尤为明显.抗CD40mAb和抗CD40LmAb也能影响Th2细胞因子的表达.其中以阻断CD40分子的作用更为显著.结果提示B7/CD28和CD40/CD40L共刺激信号可以调节Th1/Th2细胞因子的表达水平和调控Th1/Th2免疫偏移.干预B7/CD28和CD40/CD40L 介导的共刺激信号调控Th1/Th2免疫偏移有可能是一种控制血吸虫卵肉芽肿病变新型的免疫治疗途径.     

B7-H6影响小细胞肺癌凝血状态的初步研究

目的:探讨B7-H6与凝血状态在小细胞肺癌中的临床意义.方法:搜集江南大学附属医院确诊小细胞肺癌标本41例及癌旁肺组织41例,免疫组化分析B7-H6表达情况,并探讨B7-H6表达与D-二聚体、血小板、凝血酶原时间、脉管内血栓发生率的关系.结果:33例小细胞肺癌发现B7-H6表达,在正常肺组织仅发现3例弱阳性染色,在B7...     

Antitumor Response of Anti-B7-H3 CAR-T Cells with Humanized scFv in Solid Tumors

We prepared a humanized alternative B7-H3 CAR(B7-H3-haCAR-T) targeting B7-H3 which contained the humanized singl-chain varinlde fragment(scFv) from humanized 8H9 Monoclonal Antibody(hu8H9m Ab). The antitumor effects of B7-H3-haCAR-T cells were evaluated in B7-H3 overexpressed tumor cells(in vitro) and B7-H3 xenograft models(in vivo). The specific tumour killing ability of B7-H3-haCAR-T in overexpressing B7-H3 tumour cells was verified by cytotoxicity and ELISA tests. In addition, B7-H3 haCAR-T c...     

~3He(~4He)-H_2碰撞体系的相互作用势及微分散射截面的理论研究

运用量子化学从头计算方法,在CCSD(T)/aug-cc-pvtz和CCSD(T)/cc-pvtz理论水平下,计算了3He(4He)-H2相互作用能数据,采用Murrell-Sorbie势函数(M-S势)拟合了3He(4He)原子与H2分子各向异性相互作用势,并用公认精确度较高的密耦方法计算了3He(4He)-H2碰撞体系的微分散射截面,总结了微分散射截面的变化规律。研究表明:拟合势不但表达形式简洁,而且较好地描述了3He(4He)-H2体系相互作用的各向异性特征。     

人共刺激分子B7-1/CD80胞外编码区cDNA的克隆及序列分析

用RT－PCR法从人外周血单核细胞克隆了编码共刺激分子B7－1／CD80胞外区的cDNA，并用Snager链终止法进行测序，结果表明，所cDNA片段的序列与GenBank中已报道的人B7－1／CD80 cDNA序列的对应部分仅有两个碱基存在差异（658位A→T，773位A→G），这为探讨B7－1／CD80分子的生物学功能奠定了基础。     

CD40L对B淋巴细胞表面分子及分泌IL-12的影响

在体外使用CD40L作用于B淋巴细胞使之活化,通过测定B淋巴细胞表面分子及分泌细胞因子的变化,探讨B淋巴细胞作为抗原递呈细胞在抗肿瘤免疫中的优势,为B淋巴细胞特异性活化细胞毒T淋巴细胞(cytotoxic T lymphocyte,CTL)进而发挥其肿瘤细胞杀伤效应奠定基础.取7名健康成人外周静脉血,经淋巴细胞分离液分离人外周血单个核细胞(PBMC),分为对照组和实验组,实验组培养液中加入加入CD40L和IL-4,共培养21 d.观察B淋巴细胞生长状况,并在第7 d、第14 d和第21 d,用流式细胞仪(FCAS)测定其表面分子CD80、CD86和CD19,在第21 d,使用酶联免疫吸附法(ELISA)测定培养液中的IL-12水平.结果显示,在CD40L的作用下,B淋巴细胞呈克隆样增殖,并高表达表面分子CD80/CD86和CD19,和对照组相比,B淋巴细胞分泌IL-12水平升高(P＜0.05).上述实验结果说明通过CD40L的刺激,B淋巴细胞得到了活化,提示通过该途径活化的B淋巴细胞具备了作为抗原递呈细胞而发挥其抗肿瘤免疫治疗的能力.     

平面B_nBe(n=1～7)团簇的结构和稳定性理论研究

运用密度泛函理论(DFT)对平面B n Be(n=1～7)的结构、稳定性及势能面进行了计算.通过计算得到了B n Be(n=1～7)团簇的最稳定结构.值得注意的是,B n Be(n=1～7)团簇的结构模式转变发生在n=1到n=2之间.平均原子成键能(BE)、成键能增量(IBE)、能量二次差分(Δ2E)和能隙(ΔE)的变化图揭示了B4Be和B7Be具有较高的稳定性.结果表明,B n Be(n=1～7)团簇的稳定性与离域π分子轨道、σ正切分子轨道和σ径向分子轨道的相互作用有关.价分子轨道和核独立化学位移(NICS)的分析证明异构体B n Be(n=2～5)都具有π-芳香性.理论分析表明,B4Be具有σ-和π-双芳香性.有趣的是,在CCSD(T)/6-311+G(d)//B3LYP/6-311+G(d)水平上,B4Be是热力学上和动力学上稳定的,可能在将来的实验中观察到.     

^3He（^4He）-H2碰撞体系的相互作用势及微分散射截面的理论研究

运用量子化学从头计算方法,在CCSD（T）／aug—cc—pvtz和CCSD（T）／cc-pvtz理论水平下,计算了^3He（^4He）-H2相互作用能数据,采用Murrell—Sorbie势函数（M-S势）拟合了^3He（^4He）原子与H2分子各向异性相互作用势,并用公认精确度较高的密耦方法计算了^3He（^4He）-H2碰撞体系的微分散射截面,总结了微分散射截面的变化规律。研究表明：拟合势不但表达形式简洁,而且较好地描述了^3He（^4He）-H2体系相互作用的各向异性特征。     

ICOS co-stimulatory receptor is essential for T-cell activation and function

T-lymphocyte activation and immune function are regulated by co-stimulatory molecules. CD28, a receptor for B7 gene products, has a chief role in initiating T-cell immune responses. CTLA4, which binds B7 with a higher affinity, is induced after T-cell activation and is involved in downregulating T-cell responses. The inducible co-stimulatory molecule (ICOS), a third member of the CD28/CTLA4 family, is expressed on activated T cells. Its ligand B7H/B7RP-1 is expressed on B cells and in non-immune tissues after injection of lipopolysaccharide into animals. To understand the role of ICOS in T-cell activation and function, we generated and analysed ICOS-deficient mice. Here we show that T-cell activation and proliferation are defective in the absence of ICOS. In addition, ICOS -/- T cells fail to produce interleukin-4 when differentiated in vitro or when primed in vivo. ICOS is required for humoral immune responses after immunization with several antigens. ICOS-/- mice showed greatly enhanced susceptibility to experimental autoimmune encephalomyelitis, indicating that ICOS has a protective role in inflammatory autoimmune diseases.     

Can B cells turn on virgin T cells?

The first event in the initiation of an immune response is the capture and presentation of antigen to T cells. Such presentation involves two distinct steps: (1) display of the antigen, which requires uptake, processing and re-expression of the antigen in association with MHC molecules on the presenting cell surface; and (2) triggering, in which the presenting cell provides signals leading to the activation of the responding T cell. Two sorts of cells can capture antigens, the 'professional' antigen-presenting cells (APCs) such as dendritic cells and macrophages, and the B cells. Both types of cells can display antigens and the APCs are known to be able to trigger resting T cells. But despite in vitro evidence that certain B-cell types can reactivate previously-activated T cells, it is not yet clear whether a B cell can initiate an immune response by providing the signals necessary to activate a resting T cell. We reasoned that resting B cells should not have this capacity because of the problems this would present with tolerance to self idiotypes. By exploiting the unique properties of the avian haematopoietic system, we have examined the presenting capacity of B cells in vivo and found that resting B cells are indeed unable to activate resting T cells.     

Crystal structure of the B7-1/CTLA-4 complex that inhibits human immune responses

Optimal immune responses require both an antigen-specific and a co-stimulatory signal. The shared ligands B7-1 and B7-2 on antigen-presenting cells deliver the co-stimulatory signal through CD28 and CTLA-4 on T cells. Signalling through CD28 augments the T-cell response, whereas CTLA-4 signalling attenuates it. Numerous animal studies and recent clinical trials indicate that manipulating these interactions holds considerable promise for immunotherapy. With the consequences of these signals well established, and details of the downstream signalling events emerging, understanding the molecular nature of these extracellular interactions becomes crucial. Here we report the crystal structure of the human CTLA-4/B7-1 co-stimulatory complex at 3.0 A resolution. In contrast to other interacting cell-surface molecules, the relatively small CTLA-4/B7-1 binding interface exhibits an unusually high degree of shape complementarity. CTLA-4 forms homodimers through a newly defined interface of highly conserved residues. In the crystal lattice, CTLA-4 and B7-1 pack in a strikingly periodic arrangement in which bivalent CTLA-4 homodimers bridge bivalent B7-1 homodimers. This zipper-like oligomerization provides the structural basis for forming unusually stable signalling complexes at the T-cell surface, underscoring the importance of potent inhibitory signalling in human immune responses.     

T-cell co-stimulation through B7RP-1 and ICOS

T-cell activation requires co-stimulation through receptors such as CD28 and antigen-specific signalling through the T-cell antigen receptor. Here we describe a new murine costimulatory receptor-ligand pair. The receptor, which is related to CD28 and is the homologue of the human protein ICOS, is expressed on activated T cells and resting memory T cells. The ligand, which has homology to B7 molecules and is called B7-related protein-1 (B7RP-1), is expressed on B cells and macrophages. ICOS and B7RP-I do not interact with proteins in the CD28-B7 pathway, and B7RP-1 co-stimulates T cells in vitro independently of CD28. Transgenic mice expressing a B7RP-1-Fc fusion protein show lymphoid hyperplasia in the spleen, lymph nodes and Peyer's patches. Presensitized mice treated with B7RP-1-Fc during antigen challenge show enhanced hypersensitivity. Therefore, B7RP-1 exhibits co-stimulatory activities in vitro and in vivo. ICOS and B7RP-1 define a new and distinct receptor-ligand pair that is structurally related to CD28-B7 and is involved in the adaptive immune response.     

Selective attraction of monocytes and T lymphocytes of the memory phenotype by cytokine RANTES.

An important process in the immune response is the migration of different populations of lymphocytes at the proper time to sites of antigenic challenge. Although several chemoattractants are known for broad classes of lymphocytes, such as T and B cells, the process by which lymphocytes of specific subsets, such as helper, cytotoxic or memory T cells, migrate to the appropriate sites remains obscure. Interleukin-8 is a chemoattractant for T cells and neutrophils and is a member of a superfamily of soluble molecules related by a conserved motif containing four cysteine residues. IL-8 and related molecules, including platelet factor 4, constitute the C-X-C class of the superfamily and a group of cytokines produced by haematopoietic cells constitute the RANTES/sis or C-C class. The roles of most of these molecules are not well known, although murine MIP-1 alpha of the C-C branch is a specific inhibitor of haematopoietic stem cell proliferation and some members of the C-X-C branch are neutrophil-targeted inflammatory agents. Here we report that the RANTES protein of the C-C class causes the selective migration of human blood monocytes and of T lymphocytes expressing the cell surface antigens CD4 and UCHL1. CD4+/UCHL1+T cells are thought to be prestimulated or primed helper T cells involved in memory T cell function. The preferential attraction of T-cell subsets by specific cytokines could in part explain how lymphocytes are targeted, and may provide insight into the workings of T cell memory.     

Gamma-interferon is one of several direct B cell-maturing lymphokines

Two classes of molecules often released after the interaction of T lymphocytes, macrophages and antigen are B-cell maturation factors (BMF)1-3 and immune (gamma) interferon (IFN-gamma)4-7. BMFs directly induce the maturation of resting B lymphocytes to the state of active immunoglobulin secretion, while IFN-gamma is defined by the reduction of viral infectivity in vitro. However, interferons have been shown to have a variety of effects and they have also been reported both to increase and decrease B-cell differentiation in intact animals and complex cellular mixtures in vitro. Here we show that murine IFN-gamma produced by recombinant DNA technology shows similar biological effects to BMFs from two other sources. All three preparations induce immunoglobulin secretion by both normal resting murine splenic B cells and the comparable B-cell tumour line WEHI-279.1 (refs 1, 3). IFN-gamma and the other two BMFs are not identical, however, as anti-IFN-gamma antibodies block the effects on B cells of IFN-gamma, but not those of the other two lymphokines. IFN-gamma may be one of several molecules with a direct role in driving the maturation of resting B cells to active immunoglobulin secretion.     

Receptors for B-cell stimulatory factor-1 expressed on cells of haematopoietic lineage

B-cell stimulatory factor-1 (BSF-1) is a T-cell product of relative molecular mass 20,000 (Mr, 20K) initially described as a cofactor required for DNA synthesis by resting mouse B cells stimulated with low concentrations of anti-IgM antibodies. It acts on resting B cells to enhance the expression of class II major histocompatibility complex (MHC) molecules, to prepare these cells to respond more promptly to subsequent stimuli, such as anti-IgM antibodies, and causes the secretion of IgG1 and IgE by B cells stimulated with lipopolysaccharide (LPS). BSF-1 has been shown to stimulate T cell lines, resting T cells and some mast cell lines. Recently, the designation interleukin-4 (IL-4) has been suggested for BSF-1. We report here the existence of high-affinity cell-surface receptors specific for BSF-1 on both B and T lymphocytes, and on cells of several other haematopoietic lineages, including mast cell, macrophage and undifferentiated haematopoietic cell lines. Resting B and T lymphocytes express receptors, which increase in number upon activation of B cells with LPS or anti-IgM, and of T cells with concanavalin A. Cross-linking of 125I-labelled-BSF-1 to its receptors creates a complex of Mr approximately 80,000.     

A soluble form of CD4 (T4) protein inhibits AIDS virus infection

CD4 (T4) is a glycoprotein of relative molecular mass 55,000 (Mr 55K) on the surface of T lymphocytes which is thought to interact with class II MHC (major histocompatibility complex) molecules, mediating efficient association of helper T cells with antigen-bearing targets. The CD4 protein is also the receptor for HIV, a T-lymphotropic RNA virus responsible for the human acquired immune deficiency syndrome (AIDS) (refs 4-7). To define the mechanisms of interaction of CD4 with the surface of antigen-presenting cells and with HIV, we have isolated the CD4 gene and expressed this gene in several different cellular environments. Here we describe an efficient expression system in which a recombinant, soluble form of CD4 (sCD4) is secreted into tissue culture supernatants. This sCD4 retains the structural and biological properties of CD4 on the cell surface, binds to the envelope glycoprotein (gp110) of HIV and inhibits the binding of virus to CD4+ lymphocytes, resulting in a striking inhibition of virus infectivity.     

Role of the HTLV-III/LAV envelope in syncytium formation and cytopathicity

Acquired immune deficiency syndrome (AIDS) is characterized by marked depletion of the T4+ helper subset of T cells. The aetiological agent of the disease, the human T-lymphotropic virus type III (HTLV-III)/lymphadenopathy-associated virus (LAV), specifically kills T4+ cells in vitro. Part of this specificity for the T4+ population residues in the relative efficiency with which HTLV-III infects these cells, as a result of a specific interaction between the T4 molecule and the virus envelope glycoprotein. In addition, the cytotoxic consequences of HTLV-III replication are dependent on cell type, as certain lymphoid and myeloid cells can be productively infected without notable cytopathic effect. Here we investigate the basis for the specific cytotoxicity of the virus, and report that high-level expression of the HTLV-III envelope gene induces syncytia and concomitant cell death in T4+ cell lines but not in a B-lymphocyte line. Syncytium formation depends on the interaction of envelope-expressing cells with neighbouring cells bearing surface T4 molecules. These results explain, at least in part, the specific cytopathic effect of HTLV-III infections.     

Lectin-induced expression of DR antigen on human cultured follicular thyroid cells

HLA-DR antigens, the human equivalent of mouse I region-associated or Ia products, are polymorphic cell surface sialoglycoproteins involved in initiation of the immune response. Their expression is normally restricted to B lymphocytes, macrophages, dendritic and other antigen-presenting cells and vascular endothelium and possibly some cells of the mucosa lining body cavities. HLA-DR expression can be modified during cell differentiation; B lymphocytes become negative on maturing to plasma cells and human T lymphocytes acquire these antigens when activated in vitro or in vivo. We report here that human thyroid follicular cells which are normally negative for HLA-DR molecules, can be induced to express these antigens when cultured with phytohaemagglutinin (PHA), concanavalin A (Con A) or pokeweed mitogen (PWM). These lectins exert their action directly on the thyroid cells with no concomitant mitogenic effect.