人工抗原呈递细胞诱导CML28特异性T淋巴细胞杀伤急性白血病细胞的研究

目的 探讨以人工抗原呈递细胞模拟树突细胞(DC)体外诱导特异性T淋巴细胞活化、增殖,观察特异性T淋巴细胞杀伤白血病细胞的效应.方法 用慢性粒细胞白血病细胞特异性抗原肽(CML28)作为目标肽,并以磁珠同时负载人工合成的HLA-A2-Ig二聚体-抗原肽(CML28)复合物以及B7-1分子,作为诱导T淋巴细胞的活化、增殖的双信号分子,模拟抗原呈递细胞的生物功能,建立一种人工抗原呈递细胞;从HIA-A2健康骨髓捐献者骨髓或外周血中分离出单个核细胞作为效应细胞,并与人工抗原呈递细胞共孵育,以流式细胞术检测特异性T淋巴细胞活化、增殖程度.以初治急性白血病细胞作为靶细胞,将特异性T淋巴细胞与白血病细胞分别以5:1,10:1,20:1,40:1,80:1比例共孵育4 h,用乳酸脱氢酶(LDH)释放实验检测杀伤急性白血病细胞的效果.结果 以该人工抗原呈递细胞刺激T淋巴细胞后,其CML28特异性T淋巴细胞比例明显增高,实验组中抗原肽ALFCGVACA、FLQGDTSVL、DLMSSTKGL、VLTFALDSV所诱导的特异性T淋巴细胞比例分别为(13.5±1.6)%、(15.2±1.5)%、(14.7±1.8)%、(34.3±3.5)%,与对照组[(2.2±0.4)%]比较,差异均有统计学意义(P<0.01).当效应细胞与靶细胞分别以5:1,10:1,20:1,40:1,80:1混合后,随着效应细胞的增加,诱导杀伤急性白血病细胞效率也明显增强,与对照组比较,差异均有统计学意义(P<0.05).结论 以磁珠为平台的人工抗原呈递细胞能有效模拟人抗原呈递细胞,诱导T淋巴细胞特异性杀伤白血病细胞,为白血病的免疫治疗提供了一种新的途径.     

重组人粒细胞集落刺激因子动员对淋巴细胞功能相关抗原1／细胞间黏附分子1信号途径诱导CD4^＋T淋巴细胞活化及增殖的影响

目的：观察在异基因外周血造血干，祖细胞移植中重组人粒细胞集落刺激因子动员对淋巴功能相关抗原1/细胞间黏附分子1信号途径诱导的外周血CD4＋T淋巴细胞的影响，验证重组人粒细胞集落刺激因子动员对淋巴细胞功能相关抗原1/细胞间黏附分子1信号通路的抑制作用。 方法：选择2006—06/2007—06在解放军总医院血液科异基因外周血造血干细胞移植前进行重组人粒细胞集落刺激因子动员的10例健康供者，对治疗方案均知情同意，且得到医院伦理道德委员会批准。给予重组人粒细胞集落刺激因子10μg，（kg·d）进行动员，在动员前1天和动员后第5天取供者外周静脉血，用miniMACS磁珠分选系统分离纯化CD4＋T淋巴细胞，分别用CD3单克隆抗体OKT3＋细胞间黏附分子1、佛波酯＋离子霉素刺激活化CD4^＋T淋巴细胞，用双色荧光标记检测动员前后CD4^＋T淋巴细胞激活后活化标记CD69，CD25的表达；用四甲基偶氮唑盐法检测动员前后OKT3＋细胞间粘黏附分子1、佛波酯＋离子霉素刺激CD4^＋T淋巴细胞增殖能力变化。 结果：①纯化后CD4^＋T淋巴细胞纯度均在90％以上。②动员后OKT3＋细胞间黏附分子1组、佛波酯＋离子霉素组CD4^＋T淋巴细胞活化标记CD69和CD25的表达均明显低于动员前（P〈0．01）。②动员后OKT3＋细胞间黏附分子1组、佛波酯＋离子霉素组CD4^＋T淋巴细胞增殖率均明显低于动员前（P〈0．05）。 结论：重组人粒细胞集落刺激因子动员可能抑制了淋巴功能相关抗原1/细胞间黏附分子1协同刺激信号，从而使CD4^＋T淋巴细胞活化、增殖能力下降。     

骨髓增生异常综合征淋巴细胞亚群及其激活状态的分析

本研究探讨骨髓增生异常综合征（MDS）患者外周血T细胞亚群，B细胞，NK细胞数量及激活状态的临床意义．采用流式细胞术对30例MDS患者外周血T细胞，B细胞，NK细胞及其表面活化分子CD28，CD45RA，CD45RO，CD69，HLA—DR的表达进行检测和分析。30例MDS患者中低危组（RA＋RAS）22例，高危组（RAEB＋RAEBT）8例。结果表明：MDS组T细胞（CD3^＋细胞）的百分率低于正常对照组，CD4^＋CD45RA^＋细胞（未致敏CD4^＋细胞）的数值低于正常对照组。MSD组早期活化T细胞（CD3^＋CD69^＋细胞）和晚期活化T细胞（CD3^＋HLA—DR^＋细胞）的数值均显著高于正常对照组。低危组（RA和RAS）主要表现为T细胞活化功能的改变：早期活化T细胞（CD3^＋CD69^＋细胞）和晚期活化T细胞（CD3^＋HLA—DR^＋细胞）比例均增高，以及B细胞数量的减少。高危组（RAEB和RAEBT）主要表现为T细胞亚群数量的改变：CD3^＋细胞，CD3^＋CD4^＋CD8^-细胞（T辅助细胞）数量的减少，CD3^＋细胞HLA—DR和CD69的表达并不增高。NK细胞数量减少。结论：MDS病人存在有T细胞数量和功能的异常，且随着病情的进展而发生改变，所以T细胞亚群及活化功能的检测对于判断疾病的进程和指导治疗具有重要的意义。     

树突状细胞及其与脓毒症关系的研究进展

树突状细胞（dendritic ceils，DCs）是功能最强的抗原呈递细胞（antigenpresenting cell，APC），具有典型的树突状形态，膜表面高表达主要组织相容性抗原复合物Ⅱ（MHCⅡ）分子。它能移行至淋巴器官，刺激初始型T细胞增殖，并具有一些相对特异性表面标志的细胞。因此．DC被认为是免疫反应的启动者，其广泛存在于淋巴和非淋巴组织中，维持机体内环境稳定。     

LMP2混合肽负载树突状细胞与EB病毒感染患者外周血单个核细胞共培养产生识别EB病毒抗原的T细胞

LMF2是EB病毒感染细胞后表达的一种蛋白。本研究探讨应用适于不同HLA分型的EB病毒-LMF2抗原混合肽（MIX—LMF2）体外刺激EB病毒感染患者外周血单个核细胞，诱导产生EB病毒抗原特异性的细胞毒性T淋巴细胞（CTL）。取EB病毒相关噬血细胞综合症患者的外周血，分离并诱导培养树突状细胞，在培养过程中用EB病毒MIX—LMF2混合肽刺激，促成熟后在体外激活自体T淋巴细胞，每周刺激1次，共刺激2次；同时对部分分离的淋巴细胞在培养过程中不予以刺激作为对照。用基因扫描T细胞受体（TCR）B基因图谱的方法观察培养前后的T细胞克隆分布变化；用流式细胞术检测T淋巴细胞的表型变化；将培养的细胞和靶细胞共培养检测IFN—γ的分泌以研究CTL细胞抗原特异性的细胞毒作用。研究结果表明，基因扫描TCRβ基因结果显示体外培养改变了患者的TCRβ基因图谱，培养前为寡克隆的TCRβ基因家族在培养后出现与正常人相似的多峰分布，提示淋巴细胞亚群分布恢复正常；流式细胞分析显示培养前的淋巴细胞CD3^＋、CD3^＋ CD8^＋、CD^＋ CD45RA^- CD45RO^＋比例分别为70．73％、42．99％、27．56％。用负载EB病毒LMF2肽2次刺激体外培养后，上述的淋巴细胞表型分别升高为95．17％、52．54％、81、41％。NK细胞（CD3^- CD56^＋）、调节性T细胞（CD4^＋CD25^＋FOXP3^＋）比例变化不大，分别从培养前的2.12％，0．03％变化为2.35％．0．02％。CD3^＋ CD45RA^- CD45RO^＋细胞增长比例较大，表明2次刺激后大部分的初始型T淋巴细胞被激活。IFN—γ分泌检测结果显示。当负载LMF2肽的DC细胞作为靶细胞时，刺激1次的细胞分泌IFN—γ量和刺激2次的细胞分泌IFN-γ量明显高于同期未刺激细胞分泌IFN-γ量（P〈0．05）。而对于未负载LMP2的DC细胞作为靶细胞时，IFN-γ检测结果则显示无统计学意义（P〉0.05）。结论：用负载EB病毒MIX—LMF2肽的树突状细胞（De）刺激T淋巴细胞的培养方法。可以改变患者T淋巴细胞克隆分布，产生识别EB病毒的特异性T淋巴细胞。     

人骨髓间充质干细胞对T淋巴细胞的免疫调节作用

为了探讨人骨髓间充质干细胞（mesenchymal stem cell，MSC）体外对T淋巴细胞的免疫调节作用，从人骨髓液中分离培养MSC，通过细胞形态、免疫组织化学及流式细胞术检测其表面标记进行鉴定；将植物血凝素（PHA）及从人脐血中分离培养的树突状细胞（dendritic cell，DC）作为刺激因素，经磁珠分选的人CD2^＋ T淋巴细胞作为反应细胞．用^3H—TdR标记β液体闪烁计数仪检测与MSC共培养前后T淋巴细胞增殖能力的变化；用流式细胞术检测与MSC共培养10天后的CD2^＋ T细胞内各亚群Th1、Th2、Tc1、Tc2比例的变化。结果表明：MSC能明显抑制由DC诱导的T淋巴细胞增殖（P=0．004），同时MSC抑制由PHA引起的T细胞增殖，但不具有显著性差异（P=0．26），MSC培养上清液单独并不具备抑制T细胞增殖的作用，与MSC共培养后的T细胞亚群中，Th2及Tc2亚群含量较共培养前明显增加（P〈0．05）。结论：MSC对由DC和PHA诱导的淋巴细胞增殖反应均具有抑制作用，并且这种作用可能与细胞间相互作用及诱导T细胞亚群的改变有关。     

间充质干细胞对活化T淋巴细胞的免疫调节作用

本研究的目的是探讨骨髓间充质干细胞（MSC）对活化T淋巴细胞的免疫调节作用及其在allo—HSCT相关GVHD防治中的作用。用终浓度为10μg/ml的PHA于不同时间作用T淋巴细胞，以^3H—TdR掺入法检测T细胞增殖功能；以不同数量的MSC分别与活化T淋巴细胞作用，根据MSC数量不同实验分为A组（对照组，不加MSC）、B组（MSC2×10^4）、C组（MSC4×10^4）、D组（MSC8×10^4），用^3H—TdR掺入法检测作用前后T细胞功能，FCM检测细胞免疫表型。结果显示，在终浓度为10μg／ml PHA作用下，T淋巴细胞的增殖能力随培养时间的延长而增强，48小时达高峰。FCM检测MSC细胞表型表明：CD44、CD105、CD29、FIK1表达阳性，不表达CD33、CD34、CD45、HLA—DR。随着MSC数量增加，与共培养前相比，T细胞的SI值逐渐降低（P〈0．05），但C组和D组间比较无差异（P〉0．05）。在低数量MSC作用下，CD3^＋CD4^＋表达低于对照组（P〈0．05），CD4^＋CD25^＋、CD4^＋CD152^＋高于对照组（P〈0．05）；C组和D组与对照组相比，CD3^＋CD4^＋表达明显降低（P〈0．01），CD3^＋CD8^＋、CD4^＋CD25^＋、CD4^＋CD152^＋明显增高（P〈0．01）。结论：丝裂原PHA可以使T细胞活化；骨髓MSC在体外可以使活化T细胞功能和细胞免疫表型发生改变，下调CD3^＋CD4^＋的表达，上调CD3^＋CD8^＋、CD4^＋CD25^＋、CD4^＋CD152^＋的表达。     

应用免疫球蛋白重链可变区上框架区来源的抗原九肽获得的细胞毒T细胞功能分析

目的明确存B淋巴细胞肿瘤表面的免疫球蛋白重链可变区(IgHV)的框架区(FR)上是否存在可以激发细胞毒T淋巴细胞(CTL)的抗原表位，这些来源于FR的抗原肽是否能够激发家族特异性的免疫反应，探讨按照B淋巴细胞肿瘤的IgHV基因分型进行家族性的免疫治疗的可能性，方法利用生物信息学系统预测了40例B淋巴细胞肿瘤表面的免疫球蛋白序列的抗原表位，人工合成不同基因家族的抗原几肽，利用1、2细胞结合实验检测预测的抗原肽和HLA分子的亲合力利用体外CTL刺激扩增体系。诱导特异性的CTL细胞增殖，用肽／HLA四聚体检测特异性CTL的数目，应用LDH释放实验检测CTL的细胞毒活性并验证其家族特异性。结果在B淋巴细胞肿瘤的7个IgHV基因家族中找到了12个高亲和力的抗原九肽，其中10个(83％)位于FR，以HLA-A*0201正常供的外周血单个核细胞(PBMNC)负荷该九肽作为抗原呈递细胞去刺激自身PBMNC，经过4轮刺激，CD8和肽／HLA四聚体双阳性细胞从0．38％上升到49．38％LDH释放实验证明对HLA—A*0201( )、IgHV1( )靶细胞有明显的杀伤作用，并且被IgHV1肽刺激出的CTL不能识别负荷IgHV3肽的靶细胞：结论IgHV基因FR抗原儿肽可以刺激产生具有HLA限制性的并且肽特异性的CTL，同时这样的杀伤作用具有家族特异性，以此为靶位有望对B淋巴细胞肿瘤进行家族特异性的免疫治疗。     

甲状腺功能亢进症患者药物治疗前后外周血树突细胞亚群的变化

甲状腺功能亢进症（简称甲亢）是抑制性T淋巴细胞功能缺陷的一种自身免疫性疾病。树突细胞（dendritic cell，DC）是专职的抗原提呈细胞，DC根据细胞表型常分为2个亚群：DC1表面标志为Lin-人白细胞抗原（HLA）DR^＋CD11c^＋CD123^-，主要发挥抗原提呈的功能，促进细胞免疫的发生；DC2表面标志为Lin—HLA DR^＋CD11c^-CD123^＋，主要产生Ⅰ型干扰素（IFN-α），促进体液免疫的发生。     

抗B7分子抗体诱导T细胞免疫耐受研究

目的：联合应用抗B7分子的单克隆抗体（单抗）体外诱导T细胞免疫耐受模型，并探讨B7分子在T细胞免疫耐受中的作用及其机制。方法：体外联合应用抗B7单抗诱导T细胞免疫耐受，^3H-TdR掺入法检测T细胞增殖，逆转录－聚合酶链反应（RT－PCR）检测T细胞细胞因子mRNA合成。为了排除其它粘附分子的作用，应用联合转染DR7或（和）B7分子基因的CHO细胞系作为人工抗原递呈细胞（APC）介导混合淋巴细胞反应（MLR）。结果：T细胞增殖实验显示，B7－1（CD80）和B7－2（CD86）单抗单独应用可以部分阻MLR,人中CD86单抗的阻断作用更为明显。两种抗体联合应用时，可以明显阻断MLR。RT－PCR显示：应用抗B7单抗联合阻断后24h,IFN-γ及IL－2 mRNA合成明显减少，而IL－4 mRNA合成较前明显增加。人工APC介导的MLR显示，仅有第一信号（DR7）时也可以使T细胞增殖，但需要达到一定的信号强度。给予DR7信号同时给予共刺激信号CD80可以增强T细胞反应，增强效应可以被抗CD80单抗所阻断。结论：B7分子在T细胞免疫反应中具有重要的作用，可以非特异性增强T细胞免疫反应。阻断B7／CD28信号传导通路，可以诱导T细胞免疫耐受形成，其中CD86分子的作用可能更为重要。抗B7单抗诱导的T细胞无反应性后，向Th2方向分化，这可能是阻断B7分子共刺激后T细胞免疫耐受形成的机制之一。     

Engineering artificial antigen-presenting cells to express a diverse array of co-stimulatory molecules.

To facilitate the therapeutic application of antigen-presenting cells (APCs), we have developed a cell-based artificial APC (aAPC) system by engineering K562 cells with lentiviruses to direct the stable expression and secretion of a variety of co-stimulatory molecules and cytokines. Here we report the use of a combinatorial lentiviral gene transfer approach to achieve long-term stable expression of at least seven genes in the K562 parental cell line. Expression of various combinations of genes on the aAPC enables the precise determination of human T-cell activation requirements, such that aAPCs can be tailored for the optimal propagation of T-cell subsets with specific growth requirements and distinct functions. The aAPCs support ex vivo growth and long-term expansion of functional human CD8 T cells without requiring the addition of exogenous cytokines, in contrast to the use of natural APCs. Distinct populations of T cells can be expanded with aAPCs expressing CD137L (4-1BBL) and/or CD80. Finally, the aAPCs provide an efficient platform to expand genetically modified T cells and to maintain CD28 expression on CD8 T cells. Therefore, K562-based aAPCs have therapeutic potential for adoptive immunotherapies and vaccinations.     

Incomplete CD8(+) T lymphocyte differentiation as a mechanism for subdominant cytotoxic T lymphocyte responses to a viral antigen

CD8(+) cytotoxic T lymphocytes (CTLs) recognize antigen in the context of major histocompatibility complex (MHC) class I molecules. Class I epitopes have been classified as dominant or subdominant depending on the magnitude of the CTL response to the epitope. In this report, we have examined the in vitro memory CTL response of H-2(d) haplotype murine CD8(+) T lymphocytes specific for a dominant and subdominant epitope of influenza hemagglutinin using activation marker expression and staining with soluble tetrameric MHC-peptide complexes. Immune CD8(+) T lymphocytes specific for the dominant HA204-210 epitope give rise to CTL effectors that display activation markers, stain with the HA204 tetramer, and exhibit effector functions (i.e., cytolytic activity and cytokine synthesis). In contrast, stimulation of memory CD8(+) T lymphocytes directed to the subdominant HA210-219 epitope results in the generation of a large population of activated CD8(+) T cells that exhibit weak cytolytic activity and fail to stain with the HA210 tetramer. After additional rounds of restimulation with antigen, the HA210-219-specific subdominant CD8(+) T lymphocytes give rise to daughter cells that acquire antigen-specific CTL effector activity and transition from a HA210 tetramer-negative to a tetramer-positive phenotype. These results suggest a novel mechanism to account for weak CD8(+) CTL responses to subdominant epitopes at the level of CD8(+) T lymphocyte differentiation into effector CTL. The implications of these findings for CD8(+) T lymphocyte activation are discussed.     

To bead or not to bead

To bead or not to bead, that is the question posed by Ito et al. in this issue of the Journal of Immunotherapy. The generation of tumor-reactive T cells remains a major impediment to the wider application of adoptive cell transfer (ACT) therapy for the treatment of patients with cancer. Ito et al. used lymph nodes of mice draining implanted sarcomas as an enriched source of tumor antigen-specific cells. They investigated the ex vivo activation of the lymph node cells by artificial antigen presenting cells (aAPCs) for the production of therapeutic T cell cultures. The optimal aAPC consisted of magnetic beads coated with anti-CD3 and anti-CD28 antibodies. Short-term ex vivo culture with the aAPCs led to a selective expansion and/or activation of tumor antigen specific CD4+ cells. These results lay a solid foundation for the clinical application of bead-based T cell activation, and promote efforts to develop the therapeutic strategy of in vivo immunization, ex vivo T cell activation, and adoptive cell transfer.     

Selection of HLA-A2 restricted CML28 peptide by artificial antigen-presenting cells

Chronic myelogenous leukemia (CML) 28 is a broadly immunogenic antigen that can have an antileukemia effect. We adopted the SYFPEITHI database to predict human leukocyte antigen-A2 restricted CML28 peptide. We designed artificial antigen-presenting cells (aAPCs) by coating micro beads with human leukocyte antigen-A2-immunoglobulin dimer and CD28-specific antibody. We used the selected peptides-pulsed aAPCs to induce cytotoxic T lymphocytes (CTLs), to choose the CML28 peptide, which was best for inducing CTLs. The result showed that the peptides-pulsed aAPCs could induce CTLs and that the peptide VLTFALDSV was the best choice for significantly inducing specific CTLs.     

Antigen persistence is required throughout the expansion phase of a CD4(+) T cell response

For CD8(+) T cells, a relatively short antigen pulse seems sufficient for antigen-presenting cells to drive clonal expansion and differentiation. It is unknown whether the requirement for antigen is similarly ephemeral for CD4(+) T cells. To study the dependence of a CD4(+) T cell response on antigen persistence in a quantitatively and temporally controlled manner in vivo, we engineered a mouse line expressing a major histocompatibility complex class II-restricted epitope in dendritic cells under the control of a tetracycline-inducible promoter. Experiments tracking the proliferation of CD4(+) T cells exposed to their cognate antigen in various amounts for different time periods revealed that the division of such cells was contingent on the presence of antigen throughout their expansion phase, even in the presence of an inflammatory stimulus. This previously unrecognized feature of a CD4(+) T cell response contrasts with the proliferative behavior of CD8(+) T cells that has been documented, and it implies that the two T cell subsets might require different strategies for efficient vaccination.     

阵发性睡眠性血红蛋白尿症患者外周血淋巴细胞增殖、杀瘤活性及其对正常表型骨髓造血细胞的影响

阵发性睡眠性血红蛋白尿症 (PNH)克隆可能由于缺乏GPI锚连蛋白而逃脱免疫攻击 ,形成生长优势。本研究测定PNH患者淋巴细胞增殖反应及对K5 6 2细胞的杀伤作用 ,并与正常对照比较 ,观察其淋巴细胞功能。采用体外液体培养体系 ,应用免疫磁珠技术分选PNH患者骨髓CD34+ 及CD34- 细胞 ,分别向 2组细胞及对照细胞加入自身CD5 9+ 或CD5 9- 淋巴细胞及其培养上清液、外源性IFN γ及IL 2。培养 10天后 ,测定骨髓细胞中PNH细胞 (CD5 9- )百分数 ,观察淋巴细胞对骨髓中CD34+ 及CD34- 细胞中PNH细胞含量的影响。研究结果表明 ,对PHA的增殖反应 ,PNH患者未分选的淋巴细胞与健康对照比较、PNH患者自身CD5 9+ 与CD5 9- 淋巴细胞之间比较均无统计学差异 ,但对K5 6 2细胞的杀伤作用PNH患者未分选的淋巴细胞明显低于健康对照组 ,分别为 (5 0 .0 0± 2 8.6 7) %及 (76 .13± 10 .15 ) % (P <0 .0 5 ) ,而PNH患者CD5 9- 淋巴细胞与CD5 9+ 淋巴细胞之间无显著性差异。PNH患者骨髓细胞中加入自身CD5 9- 淋巴细胞或其培养上清液、CD5 9+ 淋巴细胞或其培养上清液、外源性IFN γ和IL 2培养后 ,CD5 9+ 细胞均有不同程度下降 ,除CD5 9+ 淋巴细胞组外 ,其他各组CD5 9+ 细胞下降与培养前比较有显著性差异 (P <0 .0 5 ) ,IFN γ及IL 2组     

Coexpression and functional cooperation of CTLA-4 and CD28 on activated T lymphocytes

T cell costimulation by molecules on the antigen presenting cell (APC) is required for optimal T cell proliferation. The B7 molecule on APC binds the T lymphocyte receptor CD28, triggering increased interleukin 2 (IL-2) production and subsequent T cell proliferation. CTLA-4 is a predicted T cell membrane receptor homologous to CD28, which also binds the B7 counter receptor, but whose distribution and function are unknown. Here we have developed monoclonal antibodies (mAbs) specific for CTLA-4 and have investigated these questions. mAbs were produced that bound CTLA-4 but not CD28, and that blocked binding of CTLA-4 to B7. CTLA-4 expression as measured by these mAbs was virtually undetectable on resting T cells, but was increased several hundred-fold during T cell activation. On activated lymphocytes, CTLA-4 was expressed equally on CD4+ and CD8+ T cell subsets and was coexpressed with CD25, CD28, and CD45RO. CTLA-4 expression was lower than that of CD28, reaching a maximum of approximately 1/30-50 the level of CD28. Despite its lower expression, CTLA-4 was responsible for much of the B7 binding by large activated T cells. Anti-CTLA-4 mAb 11D4 and anti-CD28 mAb 9.3 acted cooperatively to inhibit T cell adhesion to B7, and to block T cell proliferation in primary mixed lymphocyte culture. When coimmobilized with anti T cell receptor (TCR) mAb, anti-CTLA-4 mAbs were less effective than anti-CD28 mAb 9.3 at costimulating proliferation of resting or activated T cells. However, coimmobilized combinations of anti-CD28 and anti-CTLA-4 were synergistic in their ability to augment anti-TCR-induced proliferation of preactivated CD4+ T cells. These results indicate that CTLA-4 is coexpressed with CD28 on activated T lymphocytes and cooperatively regulates T cell adhesion and activation by B7.     

Immunologic self-tolerance maintained by CD25(+)CD4(+) regulatory T cells constitutively expressing cytotoxic T lymphocyte-associated antigen 4

This report shows that cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) plays a key role in T cell-mediated dominant immunologic self-tolerance. In vivo blockade of CTLA-4 for a limited period in normal mice leads to spontaneous development of chronic organ-specific autoimmune diseases, which are immunopathologically similar to human counterparts. In normal naive mice, CTLA-4 is constitutively expressed on CD25(+)CD4(+) T cells, which constitute 5-10% of peripheral CD4(+) T cells. When the CD25(+)CD4(+) T cells are stimulated via the T cell receptor in vitro, they potently suppress antigen-specific and polyclonal activation and proliferation of other T cells, including CTLA-4-deficient T cells, and blockade of CTLA-4 abrogates the suppression. CD28-deficient CD25(+)CD4(+) T cells can also suppress normal T cells, indicating that CD28 is dispensable for activation of the regulatory T cells. Thus, the CD25(+)CD4(+) regulatory T cell population engaged in dominant self-tolerance may require CTLA-4 but not CD28 as a costimulatory molecule for its functional activation. Furthermore, interference with this role of CTLA-4 suffices to elicit autoimmune disease in otherwise normal animals, presumably through affecting CD25(+)CD4(+) T cell-mediated control of self-reactive T cells. This unique function of CTLA-4 could be exploited to potentiate T cell-mediated immunoregulation, and thereby to induce immunologic tolerance or to control autoimmunity.     

Rapid cytotoxic T lymphocyte activation occurs in the draining lymph nodes after cutaneous herpes simplex virus infection as a result of early antigen presentation and not the presence of virus

Localized cutaneous herpes simplex virus type 1 (HSV-1) infection leads to arming and initial expansion of cytotoxic T lymphocytes (CTLs) in the draining popliteal lymph nodes (PLNs) followed by migration and further proliferation in the spleen. To accurately characterize the sequence of events involved in the activation and generation of anti-HSV CTLs, we used T cell receptor (TCR) transgenic mice specific for the immunodominant epitope from HSV glycoprotein B (gB(498-505)). We describe the detection of the initiation of antigen presentation in the draining lymph nodes by 4-6 h after infection with HSV-1. Analysis of CD69 up-regulation revealed activation of gB-specific CD8(+) T cells by 6-8 h after infection. Furthermore, we show that T cell proliferation begins no sooner than 24 h after activation and is marked by the concurrent appearance of CTL activity in the PLNs. These events are not dependent on the presence of virus in the draining lymph nodes, and suggest a requirement for recruitment of professional antigen-presenting cells to the site of T cell activation. Consequently, we have defined the initiation of the CD8(+) T cell-mediated response to cutaneous HSV-1 infection, demonstrating that the immune response to localized viral infection depends only on the appearance of cells presenting virus-derived antigen and commences with remarkable swiftness.