人参皂苷Rgl、Rh1对树突状细胞刺激T细胞增殖及LPAK抗肿瘤活性的影响

目的：观察人参皂苷Rg1，Rh1对树突状细胞(DC)刺激T细胞增殖及其对IL-2与PHA激活的杀伤细胞(DC-LPAK)对人乳头瘤细胞及L929细胞杀伤作用的影响。方法：分离培养鉴定DC，用MTT法检测Rg1及Rh1对DC刺激T淋巴细胞增殖作用的影响。用中性红摄入比色法观察DC—LPAK的杀伤活性。结果：T：DC为10：1及25：1时，仅Bg1 100μg/ml能促进T细胞增殖(P＜0．05)，而Rh1 100μg/ml则抑制T细胞增殖(P＜0．01)，同剂量的Rg1及Rh1相比有显著性差异(P＜0．05-0．01)；T：DC为10：1时，Rh10μg/ml抑制T细胞增殖，而在T：DC为25：1时则表现为促增殖作用(P＜0．05)。T：DC为50：1时，各加药组对T细胞增殖均无作用。Rg1及Rh1均能促进DC-LPAK对乳头瘤细胞的杀伤能力；在对L929杀伤实验中，效靶比为5：1时，Rg1各剂量均能显著促进DC—LPAK的杀伤活性(P＜0．01-0．05)，而Rh1仅中剂量能提高DC-LPAK的杀伤活力(P＜0．05)。结论：Rg1可增强DC刺激T细胞增殖及DC—LPAK杀伤肿瘤的细胞能力。Rh1的作用则与其剂量范围及细胞比例密切相关。     

CD4+ CD25+调节性T细胞对树突状细胞的杀伤作用

目的 探讨CD4^＋CD25^＋调节性T细胞是否对树突状细胞发挥免疫调节作用及其可能的机制。方法 用MACS（magnetic cell sorting）从BALB／c小鼠静息T细胞分离纯化CD4^＋CD25^＋T细胞，体外细胞增殖实验观察其对CD4^＋CD25^＋T细胞的免疫抑制作用；GM-CSF／IL-4培养自体小鼠骨髓来源DC，FACS（fluorescence-activated cell sorting）鉴定其表面分子特性；以CD3／CD28单克隆抗体活化CD4^＋CD25^＋调节性T细胞，FACS体外杀伤实验研究其对自体DC的调节作用，并观察穿孔素抑制剂EGTA对上述作用的影响。结果 用MACS法成功分离出CD4^＋CD25^＋T细胞，纯度可达98％，特异性表达而Faxp3基因，能明显抑制CD4^＋CD25^＋T细胞的体外增殖；骨髓来源的DC表达CDllc、MHCⅡ及少量协同刺激分子CD80、CD86；FACS体外杀伤实验证实以CD3／CD28抗体体外活化的CD4^＋CD25^＋调节性T细胞对自体DC有显著杀伤作用（P〈0．05），穿孔素抑制剂EGTA能部分抑制该杀伤效应（P〈0．05）。结论 CD4^＋CD25^＋调节性T细胞可通过杀伤作用对自体DC发挥免疫调节作用，穿孔素／颗粒酶杀伤途径可能参与其中。     

HIV-1 C亚型密码子优化gp120负载人DC疫苗的构建及体外功能

目的构建HIV-1C亚型gp120负载人树突状细胞(dentriti ccell,DC)疫苗,并对其体外功能进行初步检测。方法利用Amaxa细胞核转染技术将pcDNA3.1-gp120质粒转染至人成熟DC,以Western blot检测gp120的表达。通过流式细胞仪检测DC表面共刺激分子的变化、混合淋巴细胞反应、CD8+T细胞表面活化分子CD25的表达及其分泌IFN-γ的变化。结果通过Western blot检测,gp120在DC中得到了正确表达。经流式细胞仪检测,DC表面分子CD80表达率由刺激前的33.34%上升至43.20%,CD86表达率由刺激前的60.08%上升至90.34%;负载gp120DC刺激淋巴细胞增殖率为86.72%;CD8+T细胞表面分子CD25表达率由刺激前的5.27%上升至74.21%,IFN-γ的表达率达37%。结论负载了HIV-1gp120的人树突状细胞能够显著刺激淋巴细胞的增殖、增强CD8+T细胞表面活化分子CD25表达以及促进CD8+T细胞分泌IFN-γ,为下一步DC治疗性疫苗的体内研究奠定基础。     

血小板内皮细胞黏附分子1、细胞间黏附分子3和CD44在体外淋巴管新生中的作用

目的 探讨内皮黏附分子血小板内皮细胞黏附分子1(PECAM-1)、细胞间黏附分子3(ICAM-3)和CD44对淋巴管新生的作用。方法 用狗的胸导管分离和培养淋巴管内皮细胞。标记内皮细胞的PECAM-1、ICAM-3和CD44，在荧光显微镜和共聚焦激光扫描显微镜下观察。内皮细胞用肿瘤坏死因子(TNF-Ⅱ)或脂多糖(LPS)刺激后，再阻断PECAM-1、ICAM-3和CD44，作细胞计数和计算迁移率。制备三维凝胶淋巴管形成模型，观察管状结构的形成，测量其长度和面积，并在透射电镜下观察其特征。结果淋巴管内皮细胞表达PECAM-1：ICAM-3和CD44。在对照组以及TN-α和LPS刺激组，分别阻断PECAM-1、ICAM-3和CD44后，内皮细胞的迁移率降低，管样结构的长度和面积减少。阻断PECAM-1或CD44后，细胞的增殖数目降低，但阻断ICAM-3后细胞的增殖数目无明显变化。在半薄和超薄切片上，淋巴管内皮细胞形成的管状结构具有毛细淋巴管的形态特征。结论 体外培养的淋巴管内皮细胞表达PECAM-1、ICAM-3和CD44，这些黏附分子参与了淋巴管内皮细胞的增殖、迁移和管腔形成等淋巴管新生过程。     

ICAM-1编码基因对乙型脑炎DNA疫苗树突状细胞功能的影响

目的:研究细胞间粘附分子1(ICAM-1)编码基因对日本脑炎(JE) DNA疫苗脾脏树突状细胞功能的影响.方法:套式RT-PCR法获取BALB/c鼠ICAM-1编码基因,构建重组子pJME/ICAM-1和pICAM-1,脂质体法转染上述质粒于CHO细胞,Western blot法检测转染的CHO细胞中目的蛋白表达.实验分5组,包括:pJME/ICAM-1、pJME+ PICAM-1、pJME、JE灭活疫苗和pcDNA3.1(+)免疫组,以不同免疫原肌注免疫BALB/c小鼠,流式细胞仪检测经不同免疫原免疫鼠后脾脏DC表型、抗原吞噬功能以及混合淋巴细胞反应.结果:融合表达重组质粒pJME/ICAM-1和单质粒pICAM-1经鉴定构建正确.pJME/ICAM-1组CD11c+CD86+ DC和CD11c+ICAM-1+ DC比例分别为(6.92±1.40)％、(7.18±0.57)％,高于其它免疫组(均P＜0.05)；pJME/ICAM-1和pJME+ pICAM-1组DC表面CD80和MHCⅡ表达水平比较差异无统计学意义(P＞0.05)；pJME/ICAM-1与pJME+ pICAM-1组内吞能力明显增强,平均荧光强度分别为437.11 ±47.60、416.67±29.12,显著高于其它组(P＜0.05).比较不同免疫原对细胞分裂的作用,以pJME/ICAM-1组最强,(73.69±7.32)％ CD4+T细胞发生分裂,(45.40 ±2.57)％CD8 +T细胞发生分裂,显著高于对照组(P＜0.05).结论:ICAM-1编码基因能够促进JE DNA疫苗脾脏树突状细胞的成熟,能够提供独立或放大B7分子的协同刺激信号.     

人参皂苷Rg1、Rh1对树突状细胞刺激T细胞增殖及LPAK抗肿瘤活性的影响

目的 :观察人参皂苷Rg1,Rh1对树突状细胞 (DC)刺激T细胞增殖及其对IL 2与PHA激活的杀伤细胞 (DC LPAK)对人乳头瘤细胞及L92 9细胞杀伤作用的影响。方法 :分离培养鉴定DC ,用MTT法检测Rg1及Rh1对DC刺激T淋巴细胞增殖作用的影响。用中性红摄入比色法观察DC LPAK的杀伤活性。结果 :T :DC为 10 :1及 2 5 :1时 ,仅Rg110 0 μg ml能促进T细胞增殖 (P <0 0 5 ) ,而Rh110 0 μg ml则抑制T细胞增殖 (P <0 0 1) ,同剂量的Rg1及Rh1相比有显著性差异 (P <0 0 5～0 0 1) ;T :DC为 10 :1时 ,Rh110 μg ml抑制T细胞增殖 ,而在T :DC为 2 5 :1时则表现为促增殖作用 (P <0 0 5 )。T :DC为 5 0 :1时 ,各加药组对T细胞增殖均无作用。Rg1及Rh1均能促进DC LPAK对乳头瘤细胞的杀伤能力 ;在对L92 9杀伤实验中 ,效靶比为 5 :1时 ,Rg1各剂量均能显著促进DC LPAK的杀伤活性 (P <0 0 1～ 0 0 5 ) ,而Rh1仅中剂量能提高DC LPAK的杀伤活力 (P <0 0 5 )。结论 :Rg1可增强DC刺激T细胞增殖及DC LPAK杀伤肿瘤的细胞能力。Rh1的作用则与其剂量范围及细胞比例密切相关。     

CD4+T细胞的分裂与表面标志和细胞因子产生相关性的探讨

目的：阐明抗原特异性CD4^ T细胞的分裂、细胞表面分子的表达和细胞因子产生之间的关系。方法：从T细胞受体转基因小鼠(DO11、10)的脾和淋巴结中分离CD4^ T细胞。在抗原提呈细胞存在的情况下，经OVA多肽抗原刺激后，检测细胞的分裂、表型和细胞因子的产生。结果：经抗原刺激3天后，CD4^ T细胞分裂1-5次，细胞膜表面抗原CD25、CD44的表达随着细胞的分裂而增加，相反，CD62L和CD69随着细胞分裂次数的增加而递减。细胞因子IFN-γ、IL-4和IL-10随着细胞分裂次数的增加而递增。IL-12促进细胞的分裂，增加IFN-γ的产生，抑制IL-4和IL-10的产生。结论：当CD4^ T细胞活化后，随着细胞的分裂，其细胞膜表面分子的表达和细胞因子的产生均发生质和量的变化。     

支气管哮喘病人CD4+T细胞CD25、CD30表达状况

目的：通过观察哮喘病人外周血CD4⁺T细胞CD25、CD30表达水平，了解哮喘病人T细胞活化状态。方法：将分离出的CD4⁺T细胞分别用PPD、PHA刺激，最后用流式细胞仪检测抗原刺激前后细胞表面CD25、CD30表达水平。结果：①哮喘病人CD4⁺T细胞CD25、CD30自然表达比率均低于健康对照（P<0.05、P<0.05）。②用PHA刺激哮喘病人CD4⁺T细胞后，CD25表达水平明显高于健康对照（P<0.01），但CD30表达无差异。③PPD刺激组CD25、CD30表达与健康对照间无差异。结论：哮喘病人CD4⁺T细胞活化状态明显异常。哮喘病人的CD4⁺T细胞无刺激因素时，活化水平低下，但接受刺激后表现出高水平的活化状态。     

脐血CD123+髓系树突状细胞的生物学特性研究

探讨人脐血单核细胞在髓系树突状细胞(DC)体外诱导体系中获得的CD123 髓系DC的生物学特性。分离脐血单核细胞,用人重组的粒/单核细胞集落刺激因子(GM-CSF)和IL-4将其诱导为DC。用流式细胞仪检测DC表面共刺激分子、CD123和CD11c的表达,并用间接免疫磁珠法将其中CD123 DC加以分离纯化;激光共聚焦显微镜、扫描电镜和倒置显微镜观察CD123 DC形态;3H-TdR渗入法检测CD123 DC对同种异体T细胞的刺激能力。脐血单核细胞经GM-CSF和IL-4诱导7 d后,细胞表面高度表达HLA-DR、CD86、CD11c和CD123,低表达CD83,丧失CD14的表达,其中CD123和CD11c均匀分布于DC表面。免疫磁珠纯化后的CD123 DC呈现不成熟DC形态,除细胞体积较小外,其表面突起类似于CD123?DC。CD123 DC能明显刺激同种异体T细胞增殖,但其刺激能力较CD123?DC组低(P<0.05)。GM-CSF和IL-4培养体系中的CD123 DC可能是DC分化发育过程中更早期的未成熟髓系DC,具有独特的生物学特性。     

BTLA信号对T细胞活化的起始和早期阶段的调节作用

目的:观察BTLA分子在T细胞上的表达并探讨其在各个阶段不同时相对T细胞活化的抑制。方法:分离人外周血单个核细胞,经阴性选择磁珠分离纯化获得T淋巴细胞。检测T细胞上BTLA、CTLA-4和PD-1的表达;用CD3抗体刺激T细胞活化,比较BTLA、CTLA-4和PD-1在T细胞活化过程中的动态表达。CD3抗体联合CD28抗体活化T细胞,在不同的活化时间,MTT法检测BTLA单抗8H9对T细胞增殖的影响。GM-CSF和IL-4体外诱导单核细胞分化成未成熟DC,CD40抗体刺激DC成熟,流式检测HVEM在DC上的表达。用DC诱导T细胞活化,加入游离8H9或抗HVEM抗体,阻断HVEM和BTLA结合,MTT法检测T细胞增殖。结果:静止T细胞组成性高表达BTLA,不表达CTLA-4和PD-1分子。T细胞活化后,BTLA分子表达有所降低,然后迅速回升至高水平。CTLA-4、PD-1分子在活化后两天几乎不表达,第三天开始表达并逐渐上升。8H9可以抑制CD3和CD28抗体活化的T细胞增殖。CD3和CD28抗体预先活化T细胞24小时或48小时后,再加入8H9仍然具有抑制效应,但不如在T细胞活化之初加入8H9的抑制效应。单核细胞诱导的不成熟DC上高表达HVEM,当DC成熟后,HVEM表达降低。用游离8H9或HVEM抗体阻断DC表面HVEM与T细胞表面BTLA结合,48小时之内均明显增强了DC诱导的T细胞增殖。结论:BTLA信号可以提高T细胞的活化阈值,在T细胞活化的起始和早期阶段发挥重要的负性调控作用。     

雷帕霉素和地塞米松对小鼠树突状细胞分化成熟的调控

目的：观察雷帕霉素（rapamycin，Rap）和地塞米松（dexamethasone，Dex）对堵养的小鼠骨髓来源的树突状细胞（DC）分化发育的影响。方法：（1）用GM-CSF＋IL-4定向诱导C57BL／6小鼠骨髓细胞分化为DC，分别加入Rap或Dex，然后用脂多糖（LPS）刺激。在倒置显微镜和扫描电镜下，动态观察DC形态学E的变化。（2）通过流式细胞术（荧光抗体双标记法）测定CD11c^＋细胞的比例及CD86和MHC-Ⅱ类分子表达的变化。（3）通过单向混合淋巴细胞反应（MLR）观察，Rap和Dex处理的DC刺激BALB／c小鼠同种异基因T细胞增殖的情况。结果：（1）经Rap和Dex处理后，DC在形态学上呈现稳定不成熟状态。（2）Rap处理的细胞表面CDIlc和MHC-Ⅱ类分子的表达仅有轻度降低，而CD86的表达明显降低。Dex处理的细胞表面CDIlc的表达与Dex的剂量呈负相关，CD86和MHC-Ⅱ类分子的表达均明硅降低。两种药物处理的DC均可抵抗LPS的促成熟作用。（3）MLR的结果显示，Rap和Dex处理的DC刺激同种异基因BALB／c小鼠T细胞增殖的能力均较低。结论：Rap和Dex均可使DC处于稳定的不成熟状态。与Dex相比，Rap对骨髓造血F细胞向DC分化的过程影响较小，而且在抑制DC表面协同刺激分子CD86表达的同时，对MHC-Ⅱ类分子的表达影响较小。     

Selective increase of activation antigens HLA-DR and CD38 on CD4+ CD45RO+ T lymphocytes during HIV-1 infection.

Infection with HIV results in a progressive depletion of CD4+ T cells and leads to significant in vivo lymphocyte phenotype changes. In this regard, the expression of HLA-DR and CD38 on CD8+ T cells has been shown to increase dramatically with disease progression. We investigated the expression of both activation markers on CD4+ T cells in HIV-1-infected subjects at different clinical stages of infection and compared the in vivo activation of CD4+ T cells with parameters of viral activity and CD8+ T cell activation. Fresh peripheral venous blood was obtained from 54 HIV-infected subjects and from 28 uninfected healthy controls. Three-colour immunophenotyping of the CD4+ T cell subset showed that the proportion of CD4+ T cells expressing HLA-DR (10% in HIV-negative controls) or CD38 (62% in HIV-negative controls) was higher in asymptomatic (P < 0.05 for CD38) and symptomatic (P < 0.001 for HLA-DR and CD38) HIV-infected subjects than in controls, whereas the proportion of CD4+ T cells expressing CD45RO (54% in controls) remained relatively unchanged. Simultaneous expression of HLA-DR and CD38 on CD4+ T cells increased from 2.3% in controls to 11% (P < 0.001) in asymptomatic and 22% (P < 0.001) in symptomatic HIV-infected subjects. This relative increase of CD38 and HLA-DR expression occurred mainly on CD4+ T cells co-expressing CD45RO. Changes in expression of HLA-DR and CD38 on CD4+ T cells correlated with similar changes on CD8+ T lymphocytes, with the presence of HIV antigen in the circulation, and with the disease stage of HIV infection.     

Phenotypic Characterization of Five Dendritic Cell Subsets in Human Tonsils

Heterogeneous expression of several antigens on the three currently defined tonsil dendritic cell (DC) subsets encouraged us to re-examine tonsil DCs using a new method that minimized DC differentiation and activation during their preparation. Three-color flow cytometry and dual-color immunohistology was used in conjunction with an extensive panel of antibodies to relevant DC-related antigens to analyze lin(-) HLA-DR(+) tonsil DCs. Here we identify, quantify, and locate five tonsil DC subsets based on their relative expression of the HLA-DR, CD11c, CD13, and CD123 antigens. In situ localization identified four of these DC subsets as distinct interdigitating DC populations. These included three new interdigitating DC subsets defined as HLA-DR(hi) CD11c(+) DCs, HLA-DR(mod) CD11c(+) CD13(+) DCs, and HLA-DR(mod) CD11c(-) CD123(-) DCs, as well as the plasmacytoid DCs (HLA-DR(mod) CD11c(-) CD123(+)). These subsets differed in their expression of DC-associated differentiation/activation antigens and co-stimulator molecules including CD83, CMRF-44, CMRF-56, 2-7, CD86, and 4-1BB ligand. The fifth HLA-DR(mod) CD11c(+) DC subset was identified as germinal center DCs, but contrary to previous reports they are redefined as lacking the CD13 antigen. The definition and extensive phenotypic analysis of these five DC subsets in human tonsil extends our understanding of the complexity of DC biology.     

Role of the adhesion molecule ICAM-1 (CD54) in staphylococcal enterotoxin-mediated cytotoxicity.

Staphylococcal enterotoxin A (SEA) binds to major histocompatibility complex (MHC) class II molecules on target cells and directs human cytotoxic T lymphocytes (CTL) of irrelevant nominal specificity to mediate strong cytotoxicity against target cells. In this report we describe the importance of ICAM-1 (CD54) expression on the target cell in SEA-dependent cell-mediated cytotoxicity (SDCC), utilizing murine L cells co-transfected with HLA-DR and ICAM-1. Human CTL mediated a low but significant cytotoxicity against HLA-DR2- and HLA-DR7-transfected cells after preincubation with SEA, but no reactivity towards uncoated HLA-DR2 and HLA-DR7 cells or SEA-coated ICAM-1-transfected and untransfected L cells. In contrast, a strong cytotoxic response was mediated by CTL against L cells co-transfected with HLA-DR2/ICAM-1 and HLA-DR7/ICAM-1. Similar cytotoxic activity of the CTL was seen at a 30-fold lower effector-to-target cell ratio when comparing the HLA-DR2/ICAM-1-expressing cells with the HLA-DR2-expressing cells. SEA dose-response analysis demonstrated that the HLA-DR2/ICAM-1-expressing target cells enabled the CTL to respond to a 1000-fold lower concentration of SEA in comparison to the HLA-DR2-expressing cells. CD3+CD4+ and CD3+CD8+ cytotoxic T cell lines were equally dependent on the expression of ICAM-1 on the target cell. The strong CTL activity against HLA-DR2/ICAM-1-transfected cells could be blocked by anti-CD11a or anti-CD18 monoclonal antibodies (mAb), but not by anti-CD11b, anti-CD11c, anti-CD2 or unrelated control mAb. The great sensitivity of HLA-DR2/ICAM-1 expressing target cells to SDCC was strongly reduced by preincubation with various anti-ICAM-1 mAb but not by mAb against monomorphic HLA-DR or murine MHC class I determinants. The result in this study clearly demonstrates that efficient re-targeting of human CTL by SE is dependent on a proper interaction with the heterodimer CD11a/CD18 (Leu-CAMa, LFA-1) on the CTL and its target cell ligand ICAM-1.     

Cross-regulation of CD86 by CD80 differentially regulates T helper responses from Mycobacterium tuberculosis secretory antigen-activated dendritic cell subsets

We report that stimulation of Mycobacterium tuberculosis secretory antigen- and tumor necrosis factor alpha-matured BALB/c mouse bone marrow dendritic cells (BMDCs) with anti-CD80 monoclonal antibody up-regulated CD86 levels on the cell surface. Coculture of these BMDCs with na?ve, allogeneic T cells now down-regulated T helper cell type 1 (Th1) responses and up-regulated suppressor responses. Similar results were obtained with splenic CD11c(+)/CD8a(-) DCs but not to the same extent with CD11c(+)/CD8a(+) DCs. Following coculture with T cells, only BMDCs and CD11c(+)/CD8a(-) DCs and not CD11c(+)/CD8a(+) DCs displayed increased levels of surface CD86, and further, coculturing these DCs with a fresh set of T cells attenuated Th1 responses and increased suppressor responses. Not only na?ve but even antigen-specific recall responses of the Th1-committed cells were modulated by DCs expressing up-regulated surface CD86. Further analyses showed that stimulation with anti-CD80 increased interleukin (IL)-10 and transforming growth factor-beta-1 levels with a concomitant reduction in IL-12p40 and interferon-gamma levels from BMDCs and CD11c(+)/CD8a(-) DCs and to a lesser extent, from CD11c(+)/CD8a(+) DCs. These results suggest that cross-talk between costimulatory molecules differentially regulates their relative surface densities leading to modulation of Th responses initiated from some DC subsets, and Th1-committed DCs such as CD11c(+)/CD8a(+) DCs may not allow for such modulation. Cognate antigen-presenting cell (APC):T cell interactions then impart a level of polarization on APCs mediated via cross-regulation of costimulatory molecules, which govern the nature of subsequent Th responses.     

A monoclonal antibody, 3/22, to rabbit CD11c which induces homotypic T cell aggregation: evidence that ICAM-1 is a ligand for CD11c/CD18

The rabbit CD11c molecule has been characterized by use of a new monoclonal antibody, mAb 3/22. Expression of the p150,95 integrin (CD11c/CD18) has been shown by flow cytometry and immunohistochemistry to be restricted to monocytes, macrophages, dendritic cells and a small population of lymphocytes in peripheral blood. No expression on neutrophils could be demonstrated. Incubation of the newly derived CD8⁺ T cell line, BJ/873, with mAb 3/22 causes homotypic aggregation, which has been shown to be a cell surface event that is not dependent on intracellular signaling or on receptor cross-linking. Inhibition studies show that the ligands responsible for this aggregation are CD11c/CD 18 and ICAM-1, both of which are expressed on BJ/873. One other rabbit T cell line, K34, that also expresses p150,95 and ICAM-1, shows a similar aggregation response when stimulated with 3/22. Cell lines that express p150,95 but not ICAM-1 do not aggregate. These observations suggest that ICAM-1 is a ligand for activated p150,95.     

The role of suppressor of cytokine signaling 1 as a negative regulator for aberrant expansion of CD8alpha+ dendritic cell subset

The suppressor of cytokine signaling (SOCS) 1 is a negative regulator in multiple cytokine-related aspects to maintain immunological homeostasis. Here, we studied a role of SOCS1 on dendritic cell (DC) maturation in the mice lacking either TCRalpha chain or CD28 in SOCS1-deficient background, and found that the SOCS1 could restore acute phase of inflammatory response in SOCS1-deficient mice. The CD11c+ CD8- DC population in freshly isolated splenic DCs from normal mice highly expressed SOCS1. However, in SOCS1-deficient environment, the proportion of CD8alpha+ DCs (CD8 DCs) noticeably increased without affecting the cell number of conventional and plasmacytoid DC populations. This population revealed the CD11cdull CD8alpha+ CD11b- CD45RA- B220- phenotype, which is a minor population in normal mice. Localization of the abnormal CD8 DCs in splenic microenvironments was mainly restricted to deep within red pulp. The CD8 DCs secrete a large amount of IFN-gamma, IL-12 and B lymphocyte stimulator/B cell activation factor of the tumor necrosis factor family in response to LPS and CpG stimulation. This is responsible for the development of DC-mediated systemic autoimmunity in the old age of SOCS1-deficient mice. Moreover, the CD8 DC subsets expressed more indoleamine 2,3-dioxygenase and IL-10, and hence inhibit the allogeneic proliferative T cell response and antigen-induced Th1 responses. Therefore, SOCS1 expression during DC maturation plays a role in surveillance in controlling the aberrant expansion of abnormal DC subset to maintain homeostasis of immune system.     

A CD44 monoclonal antibody differentially regulates CD11a/CD18 binding to intercellular adhesion molecules CD54, CD102 and CD50

We have made a monoclonal anti-CD44 antibody which is able to activate the leukocyte integrin CD11a/CD18. Activated T cells strongly aggregated, and the aggregation was shown to be intercellular adhesion molecule (ICAM)-1 (CD54) and ICAM-2 (CD102) dependent. Using purified ICAM coated on plastic, only binding to ICAM-1 was increased by the CD44 antibody, whereas activation by phorbol ester increased binding to both ICAM-1 and ICAM-3. The binding to ICAM-2 was not affected by either treatment. These findings show that the CD11a/CD18 integrin can be activated in a ligand-specific manner by engagement of CD44.     

Adhesion receptors involved in clustering of blood dendritic cells and T lymphocytes.

The relationship of dendritic cells (DC) isolated from the peripheral blood to those of lymphoid tissue is, in terms of maturation and function, incompletely understood. In our present study, we have explored the molecular basis of adhesion of T cells to blood DC. Analysis of the expression of adhesion receptors on the cell surface of blood DC revealed that these cells express lymphocyte function-associated antigen (LFA)-1 (CD11a/18), ICAM-1 (CD54), LFA-3 (CD58) and CD44, but are very late antigen (VLA)-4 (CD49d) and vascular cell-adhesion molecule (VCAM)-1 negative. The LFA-1 pathway was found to play a key role in T cells-blood DC adhesion; monoclonal antibodies (mAb) against both LFA-1 and ICAM-1 strongly inhibited adhesion between those cells. Moreover, a T cell clone from an LFA-1-deficient patient showed poor binding to blood DC. The important role of LFA-1 in T cell-blood DC adhesion was also supported by the metabolic energy and divalent cation dependence of the interaction. mAb against LFA-3 and CD2 did not inhibit T cell-blood DC binding. In contrast to the strong inhibition by antibodies to LFA-1 and ICAM-1, antibodies to CD44 enhanced conjugate formation between T cells and blood DC. Together, our results show that the LFA-1/ICAM-1 pathway plays a central role in T cell-blood DC adhesion, a situation like that in T cell adhesion to lymphoid DC. However, unlike lymphoid DC, blood DC do not express VCAM-1 nor use LFA-3 for T cell binding.