未成熟树突状细胞表面CD1d分子在体外移植免疫中的作用

背景：树突状细胞具有双向免疫调节作用,成熟树突状细胞激活免疫应答,而未成熟树突状细胞则倾向诱导免疫耐受。目的：探讨鼠CD1d分子在未成熟树突状细胞诱导移植免疫耐受中的作用,以及在此过程中细胞因子的参与机制。方法：利用vIL-10转染的BALB/c小鼠未成熟树突状细胞在体外用粒细胞-巨噬细胞集落刺激因子基因、脂多糖刺激成熟,经抗CD1d（anti-CD1d）干预。观察培养后的细胞表型、细胞因子表达。为探明CD1d分子在异体T细胞存在下的免疫作用,进行不同实验条件的初次、再次混合淋巴细胞培养（1stMLC、2ndMLC）,观察T细胞增殖、细胞因子表达。结果与结论：Anti-CD1d的干预降低了未成熟树突状细胞增殖异体T细胞的能力,anti-CD1d干预的未成熟树突状细胞致敏异体T细胞后其免疫功能低下;anti-CD1d干预在异体T细胞存在时影响未成熟树突状细胞在功能上的成熟,主要表现在抑制白细胞介素12的分泌,加强白细胞介素10的分泌。     

未成熟树突状细胞表面CD1d分子在体外移植免疫中的作用

背景:树突状细胞具有双向免疫调节作用,成熟树突状细胞激活免疫应答,而未成熟树突状细胞则倾向诱导免疫耐受。目的:探讨鼠CD1d分子在未成熟树突状细胞诱导移植免疫耐受中的作用,以及在此过程中细胞因子的参与机制。方法:利用vIL-10转染的BALB/c小鼠未成熟树突状细胞在体外用粒细胞-巨噬细胞集落刺激因子基因、脂多糖刺激成熟,经抗CD1d(anti-CD1d)干预。观察培养后的细胞表型、细胞因子表达。为探明CD1d分子在异体T细胞存在下的免疫作用,进行不同实验条件的初次、再次混合淋巴细胞培养(1stMLC、2ndMLC),观察T细胞增殖、细胞因子表达。结果与结论:Anti-CD1d的干预降低了未成熟树突状细胞增殖异体T细胞的能力,anti-CD1d干预的未成熟树突状细胞致敏异体T细胞后其免疫功能低下;anti-CD1d干预在异体T细胞存在时影响未成熟树突状细胞在功能上的成熟,主要表现在抑制白细胞介素12的分泌,加强白细胞介素10的分泌。     

树突状细胞与免疫耐受

树突状细胞(DC)是目前发现体内功能最强大的专职抗原递呈细胞(APC),其主要来源于CD34+造血干细胞.依据其成熟状态的不同而发挥不同的免疫调节作用,如成熟树突状细胞(mDC)可激活T细胞促进免疫应答,未成熟树突状细胞(imDC)及调节性树突状细胞(DCreg)可负向调节免疫应答,诱导免疫耐受.DC在感染、免疫性疾病、移植免疫及恶性肿瘤的发病机制与治疗中的作用成为免疫学界研究的焦点.近年来DC诱导免疫耐受的研究受到越来越多的关注,笔者就DC在免疫耐受中的作用作一综述.     

慢病毒介导可溶性肿瘤坏死因子受体1在小鼠骨髓未成熟树突状细胞中的表达(英文)

背景:肿瘤坏死因子α是介导树突状细胞成熟的重要细胞因子之一,可溶性肿瘤坏死因子受体1与其结合可阻断肿瘤坏死因子α的作用,维持树突状细胞于不成熟状态,诱导免疫耐受.目的:构建含有人sTNFR1的慢病毒表达载体,观察其在未成熟树突状细胞中的表达.方法:以人外周血单个核细胞总RNA为模板,RT-PCR扩增出sTNFR1基因片段,亚克隆至慢病毒转移质粒pXZ208,通过IRES连接eGFP报告基因,建立双顺反子慢病毒转移质粒,命名为pXZ9-sTNFR1,DNA测序鉴定.采用脂质体转染293 FT细胞,根据报告基因eGFP测定病毒滴度.采用小剂量粒-巨噬细胞集落刺激因子+白细胞介素4体外培养扩增C57BL/6小鼠骨髓来源树突状细胞.培养第5天,以pXZ9-sTNFRl重组慢病毒上清感染未成熟树突状细胞,RT-PCR检测感染后sTNFRl转录,Westernblot法检测sTNFR1蛋白表达,观察sTNFR1基因修饰及脂多糖刺激后树突状细胞的表型特征.结果与结论:成功构建重组质粒pXZ9-sTNFR1,转染293 FT细胞24 h后观察到eGFP表达,病毒滴度在10~6U/L以上.RT-PCR显示pXZ9-sTNFR1感染的未成熟树突状细胞sTNFR1呈阳性表达,Western blot检测到sTNFR1蛋白存在于感染后未成熟树突状细胞和培养上清中.培养第5天的树突状细胞低表达CD40、CD86、CD80和MHCⅡ类分子,脂多糖刺激后,高表达MHCⅡ类分子和CD40、CD80、CD86分子,显示出成熟型树突状细胞表型特征,sTNFR修饰的树突状细胞MHC Ⅱ类分子和CD40、CD80、CD86分子表达水平无变化.提示:①成功构建了负载sTNFR1基因片段及含eGFP报告基因的慢病毒载体,获得了高滴度的重组慢病毒颗粒.②经慢病毒高效转导的未成熟树突状细胞sTNFR1 mRNA及蛋白稳定地表达,可以保护未成熟树突状细胞不被外源性脂多糖刺激活化,维持树突状细胞于非成熟状态.     

RelB shRNA慢病毒感染小鼠骨髓树突状细胞的免疫学效应

背景:沉默树突状细胞发育成熟的关键基因核因子кB/RelB可构建新型致耐受树突状细胞? 目的:探讨RelB shRNA转染小鼠骨髓树突细胞的生物免疫学功能的影响.方法:利用重组粒细胞-巨噬细胞集落刺激因子和重组白细胞介素4联合诱导小鼠骨髓树突状细胞;慢病毒载体将RelB shRNA转染致小鼠骨髓树突细胞后,分为未成熟树突状细胞、脂多糖刺激成熟、RelB基因沉默及脂多糖刺激RelB沉默的4组树突状细胞进行观察.结果:体外培养第 6 天脂多糖刺激组细胞表面可见大量细长的类似树枝的突起,其他3组细胞形态特征相似,呈圆形、皱缩状态,这3组细胞表面MHC-II类分子、CD86和CD40分子表达水平相当,但低于脂多糖刺激组;3组混合淋巴细胞反应中刺激T细胞增殖能力差异无显著性意义(P > 0.05),但均较脂多糖刺激组显著降低(P < 0.01);RelB基因沉默的树突状细胞分泌Th1细胞因子γ-干扰素和白细胞介素2的能力较低,分泌Th2白细胞介素10和白细胞介素4的能力较高(P < 0.01),Th1/Th2细胞因子的比例与未成熟树突状细胞类似.说明RelB shRNA经慢病毒转染骨髓源性树突状细胞后,在细胞形态、表面分子表达、免疫学功能等方面均具有与未成熟树突状细胞相似的特点,且不能被脂多糖刺激成熟.     

骨髓间充质干细胞干预再生障碍性贫血患者树突状细胞的成熟分化

背景：骨髓间充质干细胞对再生障碍性贫血患者T细胞增殖的影响国内仅见少量报道,而骨髓间充质干细胞是否通过调节树突状细胞来影响再生障碍性贫血患者T细胞的增殖,国内未见报道,其机制值得深入研究.目的：观察骨髓间充质干细胞对再生障碍性贫血患者树突状细胞的免疫调节作用.方法：将培养第5天的再生障碍性贫血患者外周血单个核细胞来源的树突状细胞与第3代健康人骨髓间充质干细胞混合培养,加入脂多糖、肿瘤坏死因子促树突状细胞成熟,应用流式细胞仪检测骨髓间充质干细胞与未成熟、成熟树突状细胞共培养前后树突状细胞表面标志表达.结果与结论：未成熟的树突状细胞在脂多糖的刺激诱导下与骨髓间充质干细胞共培养前后,树突状细胞表面标志CD14,CD1a,CD83,CD80表达无变化（P〉0.05）;成熟树突状细胞与骨髓间充质干细胞共培养前后,树突状细胞表面标志CD14,CD1a,CD83,CD80表达降低（P〈0.05）.结果说明骨髓间充质干细胞可抑制再生障碍性贫血患者单核细胞来源的树突状细胞的发育和成熟,进而发挥调节再生障碍性贫血患者的免疫作用.     

基于手法筛选的小鼠骨髓树突状细胞的体外培养方法

目的：通过建立简单经济的小鼠骨髓树突状细胞的体外培养方法,比较不同成熟状态下树突状细胞生物免疫学特性的变化.方法：实验于2004-07/2005-06在南方医院检验医学中心完成.①取C57B/L小鼠骨髓细胞作为树突状细胞的前体细胞.将培养的树突状细胞分成两组,未成熟树突状细胞组（粒细胞-巨噬细胞集落刺激因子＋白细胞介素4诱导）;成熟树突状细胞组（粒细胞-巨噬细胞集落刺激因子＋白细胞介素4＋脂多糖）,每天光镜观察各组细胞生长情况.第6天收集细胞,其形态采用电镜观察.②两组树突状细胞表型分析采用流式细胞仪分析.③取BALB/c小鼠脾脏细胞,分离T细胞作为反应细胞.用两组树突状细胞作为刺激细胞.按刺激细胞与反应细胞1：5,1：10,1：20,1：40的比例混合培养,并用T细胞悬液作阴性对照,观察混合淋巴细胞反应情况.结果：①树突状细胞培养的光镜观察：未成熟树突状细胞多为圆形,少量菌幕样突起;脂多糖刺激后,树突状细胞呈悬浮状态,表面较多细长突起.②树突状细胞电镜观察结果：扫描电镜示未成熟树突状细胞表面皱褶和较少的毛刺;成熟树突状细胞表面大量树枝状细长突起.透射电镜示未成熟树突状细胞形态较规则,突起较少,胞浆内有许多吞饮泡及多泡体;成熟树突状细胞形态不规则,胞内囊泡结构减少,细胞器较丰富,细胞核偏向一侧,表面有细长树枝状突起.③各组树突状细胞表型分析：未成熟树突状细胞表面中度表达主要组织相容性复合体Ⅱ类分子,低水平表达CD40,CD86和CD25;成熟树突状细胞表面高度表达主要组织相容性复合体Ⅱ类分子,高水平表达共刺激分子.④混合淋巴细胞反应：未成熟树突状细胞只能轻度刺激同种T细胞增殖;成熟树突状细胞能够刺激T细胞大量增殖.结论：采用重组小鼠粒-巨集落刺激因子和白细胞介素4联合诱导骨髓前体细胞可在体外培养出大量未成熟树突状细胞,低表达共刺激分子,体外诱导同种T细胞增殖能力较弱,呈现耐受性树突状细胞特性,有望应用于移植排斥反应及或自身免疫疾病的生物治疗.     

细胞膜表达的HLA-G诱导免疫耐受性树突状细胞的产生

为了探讨体外诱导免疫耐受性树突状细胞（dendritic cell,DC）产生的方法及其机制,利用人HLA-G1真核表达载体转染K562细胞并与DC共培养后,用流式细胞术检测DC表面CD80、CD86、ILT3和ILT4分子表达情况,同时采用氚胸腺嘧啶核苷（3H-TdR）掺入法检测DC对T细胞功能的影响。结果表明,膜表达的HLA-G1分子与树突状细胞作用后,DC表面免疫共刺激分子CD80、CD86表达下调,而抑制性分子ILT3、ILT4表达上调。HLA-G1作用后DC异基因抗原诱导淋巴细胞增殖的活性明显下降。结论：HLA-G1分子可以在体外条件下,下调DC表面免疫共刺激分子水平,促进ILT3、ILT4表达,诱导免疫耐受性树突状细胞产生。     

耐受性树突状细胞与自身免疫性疾病关系

树突状细胞（Dendritic cell，DC）是具有典型树突状形态、膜表面高表达主要组织相容性复合体-Ⅱ（MHC-Ⅱ）类分子、能移行至淋巴器官和刺激初始型T细胞增殖活化的细胞，是递呈肿瘤抗原能力最强的抗原递呈细胞（APC）。以往认为DC是激活T细胞初始免疫反应的细胞，在介导炎性反应、抗肿瘤反应中起重要作用。随着研究的深入，人们发现树突状细胞在免疫耐受中起重要作用，在抗原提呈过程中，若共刺激分子缺乏或被阻止，不但不能激活T淋巴细胞反而可以诱导对该抗原的耐受。常规培养的DC诱导产生CD4＋CD8＋效应性T细胞，激活机体产生针对抗原的免疫反应。未成熟DC在体内向初始T细胞呈递抗原，诱导产生CD4＋CD25＋调节性T细胞，其结果是诱导特异性免疫耐受。目前，全世界约有20％的人受各种自身免疫性疾病的困扰。由于自身免疫性疾病可引起各年龄阶段患者的残疾和死亡，而目前尚无有效的方法治愈此类疾病，仅仅可以延缓疾病的进展。因此，进一步探讨治疗此类疾病的方法备受关注。本文就耐受性DC与自身免疫性疾病的关系研究进展作一综述。     

树突状细胞体外成熟及免疫功能的18F-FDG评价

背景：既往研究表明,不同剂量的电离辐射对树突状细胞的成熟、免疫功能等也可能有一定的影响。目的：分析不同浓度的18 F-FDG对体外培养的人外周血单个核细胞源性树突状细胞的成熟及免疫功能的影响。方法：人外周血单个核细胞源性树突状细胞诱导成熟后,分为5组,分别加入含PBS及92.5×104,185×104,370×104,740×104 Bq/mL浓度的18 F-FDG培养基,作用24 h后收集细胞,检测树突状细胞的凋亡率、细胞表型(CD1α、CD80、CD83、CD86、HLA-DR)表达、同种混合淋巴细胞反应及细胞培养上清液中的巨噬细胞炎性蛋白1α和单核细胞趋化因子1表达。结果与结论：740×104 Bq/mL浓度的18F-FDG可以引起树突状细胞的凋亡、CD86的表达下调,同种T细胞抗原提呈能力下降,单核细胞趋化因子1的分泌下降;其余浓度的18F-FDG对树突状细胞的成熟及免疫功能无明显影响。结果表明较低浓度的18F-FDG对树突状细胞的凋亡、成熟、抗原提呈、迁移能力等影响较小,可以在选择合适浓度的前提下作为一种树突状细胞细胞的体外标记物。     

Prevention of Peripheral Tolerance by a Dendritic Cell Growth Factor: Flt3 Ligand as an Adjuvant

Injections of soluble proteins are poorly immunogenic, and often elicit antigen-specific tolerance. The mechanism of this phenomenon has been an enduring puzzle, but it has been speculated that tolerance induction may be due to antigen presentation by poorly stimulatory, resting B cells, which lack specific immunoglobulin receptors for the protein. In contrast, adjuvants, or infectious agents, which cause the release of proinflammatory cytokines such as tumor necrosis factor α and interleukin 1β in vivo are believed to recruit and activate professional antigen-presenting cells to the site(s) of infection, thereby eliciting immunity. Here we show that administration of Flt3 ligand (FL), a cytokine capable of inducing large numbers of dendritic cells (DCs) in vivo, (a) dramatically enhances the sensitivity of antigen-specific B and T cell responses to systemic injection of a soluble protein, through a CD40–CD40 ligand–dependent mechanism; (b) influences the class of antibody produced; and (c) enables productive immune responses to otherwise tolerogenic protocols. These data support the hypothesis that the delicate balance between immunity and tolerance in vivo is pivotally controlled by DCs, and underscore the potential of FL as a vaccine adjuvant for immunotherapy in infectious disease and other clinical settings.     

Inhibition of antigen-presentation attenuators to augment vaccines

Antigen-presenting cells (APCs), such as dendritic cells (DCs), play a critical role in initiating and regulating immune responses. The mechanisms utilized by APCs to sense microbes and initiate immune responses have been well studied, however, little is known about the negative regulation of APCs. Recent studies demonstrate that suppressor of cytokine signaling 1 (SOCS1) functions as an antigen-presentation attenuator by controlling the tolerogenic state of DCs and the magnitude of antigen presentation. Inhibition of SOCS1 significantly enhances the ability of DC-based tumor vaccines to break self-tolerance and to induce effective antitumor immunity. Furthermore, inhibition of this antigen-presentation attenuator drastically boosts memory HIV-specific T- and B-cell responses induced by DC- and DNA-based HIV vaccines. This novel immunization strategy of 'inhibiting antigen-presentation attenuators' would be generally applicable to enhance both therapeutic and prophylactic vaccines against tumors and pathogens.     

Acquisition and presentation of follicular dendritic cell-bound antigen by lymph node-resident dendritic cells

Follicular dendritic cells (DCs [FDCs]) are prominent stromal cell constituents of B cell follicles with the remarkable ability to retain complement-fixed antigens on their cell surface for extended periods of time. These retained immune complexes have long been known to provide the antigenic stimulus that drives antibody affinity maturation, but their role in cellular immunity has remained unclear. In this study, we show that FDC-retained antigens are continually sampled by lymph node-resident DCs for presentation to CD8 T cells. This novel pathway of antigen acquisition was detectable when FDCs were loaded with purified antigens bound into classical antigen-antibody immune complexes, as well as after pregnancy, when they are loaded physiologically with antigens associated with the complement-fixed microparticles released from the placenta into maternal blood. In both cases, ensuing antigen presentation was profoundly tolerogenic, as it induced T cell deletion even under inflammatory conditions. These results significantly broaden the scope of FDC function and suggest new ways that the complement system and persistent antigen presentation might influence T cell activation and the maintenance of peripheral immune tolerance.     

Immune dysfunction in the elderly and its reversal by antihistamines.

The decline in immunity seen in the elderly is a significant contributor to disease burden. This decline has largely been attributed to alterations in T cell immunity and contributes to an overall increased risk and severity of infection in the elderly. A key component of T cell immunity involves antigen presentation, an event where an antigen is processed and presented to specific immune cells for destruction. This event has been found to be crucial to immune function. Recent research has focused on a key antigen presenting cell (APC), the dendritic cell (DC), and changes within its function associated with aging. DCs are considered to be the most professional APCs, and are responsible for the initiation and outcome of effector T cells and their resultant immune response. DCs capture antigens and undergo a maturation process and polarize into either type 1 dendritic cells (DC1) or type 2 dendritic cells (DC2), based upon their ability to favor a T helper1 (Th1) or T helper 2 (Th2) T cell response, respectively. Evidence suggests that in normal healthy adults, a Th1 type response predominates, and in frail elders, a Th2 response predominates. It has been proposed that this change from a predominately Th1 type to a predominate Th2 type response is a possible mechanism for age-associated immune dysfunction. In addition, recent research has focused on how histamine, an inflammatory mediator, promotes a Th2 response. Histamine has also been shown to polarize human DCs into Th2 cell-promoting effector DCs or DC2s. This has been shown to occur via interaction with the H2 receptor. Therefore, we theorize that use of an H2 selective antihistamine will reverse this polarization back to a Th1 type response and therefore improve immune function of the frail elderly.     

Pro-tolerogenic effects of photodynamic therapy with TH9402 on dendritic cells

A major goal in transplantation immunology is to develop strategies that can specifically promote tolerance to foreign cells and tissues without compromising other immune functions. Experimental induction of transplantation tolerance by dendritic cells (DCs) and/or T regulatory (Treg) cells can efficiently prevent graft-versus-host disease and organ graft rejection in animal models, and there is much hope that similar strategies in transplanted patients will provide an alternative to immunosuppression. Photodynamic therapy (PDT) is a therapeutic treatment for graft versus host disease and organ rejection that may operate via induction of tolerance. We investigated whether a new PDT therapy, based on exposure of cells to 4,5-dibromorhodamine methyl ester (TH9402), may operate via induction of tolerogenic DC. We developed an in vitro model to mimic the in vivo effect of re-infusing peripheral blood mononuclear cells (PBMCs) treated with PDT based on TH9402 (TH-PDT). TH-PDT-treated PBMCs were co-cultured with allogeneic immature monocyte-derived DCs. After 24 h, the phenotype and T-cell stimulatory capacity of the DCs was assessed. Following phagocytosis of TH-PDT PBMCs, DCs maintained an immature phenotype, produced significantly increased amounts of interleukin-10, and had a reduced allostimulatory capacity in comparison to mature DCs. In the context of transplantation, these data suggest that repeated exposure of circulating DCs to TH-PDT PBMCs may result in presentation of alloantigens under anti-inflammatory conditions and induction of antigen-specific tolerance.     

奥美沙坦对大鼠树突细胞抗原递呈功能作用的研究

目的:探讨奥美沙坦对大鼠树突细胞（dendritic cells,DCs）抗原递呈功能的影响。方法:取雌性Lewis大鼠髓源DCs,加入奥美沙坦（终浓度10 μmol/L）和等体积的DMSO,分别记为奥美沙坦修饰的DCs（olmesartan modified dendritic cells,OLM-DCs）和未经奥美沙坦修饰的DCs（control DCs,Con-DCs）。使用流式细胞仪分别测定DCs表面CD80、CD86和MHC Ⅱ平均荧光强度（mean fluorescence intensity, MFI）及DCs中IL-10和TGF-β的表达。OLM-DCs和Con-DCs分别与卵白蛋白（OVA）致敏的淋巴结CD4 + T细胞共培养,流式细胞仪检测T淋巴细胞增殖,ELISA检测细胞培养上清液中IFN-γ、IL-10水平。 结果:奥美沙坦抑制了DCs表面MHC Ⅱ分子的表达,促进了IL-10的产生。与Con-DCs组比较,OLM-DCs抑制了T淋巴细胞增殖反应和IFN-γ的产生。结论:在体外,奥美沙坦能够诱导产生耐受性DCs,后者能够抑制T淋巴细胞增殖、抑制Th1细胞因子的水平。