CCK-8对内毒素血症小鼠腹腔巨噬细胞B7.1和B7.2表达及协同刺激功能的影响

目的： 探讨八肽胆囊收缩素（CCK-8）对内毒素血症小鼠腹腔巨噬细胞B7.1和B7.2表达及其协同刺激活性的影响。方法: 将BALB/c小鼠随机分组（n=4）,分别腹腔注射生理盐水（0.2-0.3 mL/mouse），LPS（100 μg/mouse）和/或CCK-8 (5 nmol/mouse)及CR1409（100 μg/mouse）、CR2945（100 μg/mouse）。12 h后收集并纯化腹腔巨噬细胞。采用流式细胞术分析细胞表面B7.1和B7.2含量的变化。用免疫磁珠从小鼠脾细胞分离CD4+T细胞，按4∶1数量比与上述处理的腹腔巨噬细胞共同体外培养，同时加入ConA 5 mg/L，采用［³H］掺入法测定CD4+T细胞增殖，反映巨噬细胞的协同刺激活性。结果: 整体应用CCK-8作用小鼠腹腔巨噬细胞，与对照组相比，CCK-8可上调静息小鼠腹腔巨噬细胞B7.2的表达，而对B7.1的表达则无影响；并且CCK-8使CD4+T细胞［³H］-TdR的掺入率升高，即促进其增殖，增强巨噬细胞的协同刺激活性。CCK-8降低LPS活化的内毒素血症小鼠腹腔巨噬细胞B7.1和B7.2的表达并且降低CD4+T细胞的［³H］-TdR掺入率，即抑制其增殖，抑制其协同刺激活性。CR1409及CR2945均能逆转CCK-8的上述作用，且CR1409的作用较CR2945更明显。结论: CCK-8通过上调巨噬细胞B7.2表达而增强其协同刺激活性；并且降低LPS活化的内毒素血症小鼠腹腔巨噬细胞B7.1和B7.2的表达，抑制其协同刺激活性。该作用由CCK1R及CCK2R共同介导，其中CCK1R起主要介导作用。     

Comparison of CD28-B7.1 and B7.2 functional interaction in resting human T cells: Phosphatidylinositol 3-kinase association to CD28 and cytokine production

CD28 is a 44-kDa homodimer present on T cells providing an important costimulatory signal for T cell proliferation, cytokine production and cytokine receptor expression. CD28 activation is mediated by interaction with its counter-receptors, B7.1/CD80 and B7.2/B70/CD86. The biochemical basis of these costimulatory signals are still poorly understood, particularly in resting T cells. However, various biochemical pathways such as tyrosine phosphorylation, phospholipase C, sphingomyelinase and phosphatidylinositol 3-kinase (PI3-K) activation have been reported to play a role in CD28 signaling in tumor T cell lines and CD28-transfected cells or pre-activated T cells. In addition, recent reports propose that CD28-B7.1 and B7.2 interaction could be involved in the production of Th1 and Th2 cytokines, respectively, but the putative biochemical basis for these different functions is still unknown. We have analyzed the functional and molecular consequences of CD28 activation by B7.1 and B7.2 in human resting T cells. We demonstrate in this report that both CD28-B7.1 and CD28-B7.2 interactions induce the association of PI3-K to CD28 in the CD4 subpopulation, whereas it was barely detectable in CD8 cells. This association involves the binding of the src homology domain 2 (SH2) of p85 to tyrosine-phosphorylated CD28 and does not require pre-activation by CD3-T cell receptor. Worthmannin, a specific inhibitor of PI3-K enzymatic activity within the nanomolar range also inhibits the interleukin-2 production induced by costimulation mediated by either the B7.1- and B7.2-transfected cells or CD28 monoclonal antibodies. The only slight difference between B7.1 and B7.2 costimulation is the IC₅₀ of wortmannin being 25 and 110 nM, respectively, which could suggest differences in their activation of the T cell PI3-K.     

B7.1基因的表达对肝癌细胞生物学特性的影响

目的　观察B7 1基因表达对肝癌细胞增殖特性的影响及诱发杀伤性T淋巴细胞 (CTL)细胞毒活性的变化。方法　用细胞计数法和流式细胞仪 (FCM)测定细胞生长曲线、DNA含量及细胞周期的变化。同时测定CTL对转染B7 1基因前后肝癌细胞的细胞毒作用。结果　转染B7 1基因后 ,肝癌细胞的增殖受到一定影响 :生长延缓、增殖幅度降低和倍增时间延长。CTL对转染B7 1基因的肝癌细胞杀伤明显增强。结论　转染B7 1基因的肝癌细胞出现了一定的增殖抑制现象 ,提示B7 1基因有一定的免疫调节作用     

Localization in situ of the co-stimulatory molecules B7.1, B7.2, CD40 and their ligands in normal human lymphoid tissue

Functional interactions between B and T lymphocytes are known to depend on the expression of co-stimulatory molecules B7.1/CD80, B7.2/CD86 and their counter-receptors CD28 and CTLA4, as well as CD40 and its ligand CD40L. To study the role of these molecules in situ, an immunohistochemical analysis was carried out on normal human lymphoid tissue. In the germinal centers (GC), B7.1 and B7.2 were differentially expressed. In the dark zone, centroblasts were predominantly B7.1⁺, while centrocytes in the light zone were B7-2⁺, resulting in reversed gradients of both markers in GC. Follicle mantle cells were negative for B7.1 and B7.2. Macrophages and interdigitating dendritic cells (IDC) in T cell zones both expressed B7.1 and B7.2. Moreover, clusters of B7.2⁺ T cells were demonstrated in interfollicular areas. Intrafollicular CD4⁺ T cells in GC, predominantly in the apical light zone, expressed CD28 and CTLA4, as did the majority of interfollicular T cells. CTLA4 showed a striking excentric cytoplasmic staining, which was also seen on T cells activated in vitro. CD40 was expressed on all B cells and more strongly on macrophages and IDC. Moreover, small clusters of T cells in a rim outside the GC showed CD40 expression. CD40L was expressed both on intrafollicular CD4⁺ T cells as well as on T cells in T cell zones. The differential distribution of co-stimulatory molecules in different compartments of normal human lymphoid tissue in situ indicates that these interactions play a distinctive role in different stages of B cell differentiation and in the immune response.     

Absence of B7.1-CD28/CTLA-4-mediated co-stimulation in human NK cells

Recent studies have suggested that B7-CD28 interactions provide co-stimulatory signals for activation of NK cells. Transduction of the B7.1 (CD80) gene into tumor cells has been shown to trigger proliferation and cytotoxicity of murine NK cells and a human NK cell line, YT2C2. Therefore, transduction of the B7.1 gene into CD80-negative human squamous cell carcinomas of the head and neck (SCCHN) and its stable expression was expected to up-regulate proliferation and cytotoxic activities of human NK cells. However, expression of the B7.1 receptors, CD28 and CTLA-4, could not be demonstrated on the surface or in the cytoplasm of normal human NK cells, irrespective of the state of their activation. In proliferation experiments or various cytotoxicity assays, utilizing highly purified human NK cells as responder or effector cells, no enhancement of NK cell generation or activity, respectively, by B7.1⁺ SCCHN was observed relative to non-transduced or LacZ gene-transduced SCCHN. In contrast, co-incubation of B7.1⁺ SCCHN targets with human NK cells induced significant inhibition of NK cell growth. Thus, the B7.1-CD28/CTLA-4 pathway is not involved in triggering of human adult NK cells.     

转人B7.2基因的L929细胞对T细胞增殖和分泌IL-10的作用

应用RT-PCR法,从由LPS刺激的人的DC细胞中抽提mRNA,扩增获得编码人B7.2分子的cDNA,并将其克隆到PMD18-T载体,经PCR、酶切及测序进行鉴定确证,进而构建PEGZ-term-B7.2的真核表达载体。脂质体法共转染包装细胞293T,用含有完整病毒颗粒的293T细胞的上清感染L929细胞,经Zeocin筛选,建立稳定表达人B7.2分子的L929基因转染细胞株。并证实了B7.2基因转染细胞能有效地促进T细胞的体外增殖和促进IL-10的分泌。     

肝癌细胞稳定转染B7.1后的免疫学特性

目的 探讨赋予肝癌细胞第二信号分子Ｂ７．１增强癌细胞与淋巴细胞之间的识别与激活作用,从而达到增强淋巴细胞对肝癌细胞的杀伤或抑制作用。方法 利用逆转录方法,转染Ｂ７．１分子至包装细胞系ＰＡ３１７。筛选获得高滴度的克隆后,以病毒上清感染肝癌细胞,使其表达Ｂ７．１分子,最后以ＬＤＨ释放法测定ＬＡＫ细胞的细胞毒活性。结果 肝癌细胞可稳定表达Ｂ７．１分子,阳性率达９４．３％,未转染的细胞无表达,其所诱发的Ｌ     

B7.1及SEA基因共转染肝癌细胞的初步研究

目的获得可表达共刺激分子B7.1和超抗原分子SEA的肝癌细胞株,检测其表达。方法用免疫组织化学方法,筛选表达B7.1及SEA的肝癌细胞阳性克隆。用流式细胞仪检测B7.1表达的阳性率,ELISA检测上清中SEA的含量。结果获得表达B7.1和SEA的肝癌细胞株,培养上清中SEA的含量达10～14×10     

Gene expression analysis of dendritic/Langerhans cells and Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is a neoplastic disorder that results in clonal proliferation of cells with a Langerhans cell (LC) phenotype. The pathogenesis of LCH is still poorly understood. In the present study, serial analysis of gene expression (SAGE) was applied to LCs generated from umbilical cord blood CD34+ progenitor cells to identify LC-specific genes and the expression of these genes in LCH was investigated. Besides the expression of several genes known to be highly expressed in LCs and LCH such as CD1a, LYZ, and CD207, high expression of genes not previously reported to be expressed in LCs, such as GSN, MMP12, CCL17, and CCL22, was also identified. Further analysis of these genes by quantitative RT-PCR revealed high expression of FSCN1 and GSN in all 12 LCH cases analysed; of CD207, MMP12, CCL22, and CD1a in the majority of these cases; and CCL17 in three of the 12 cases. Immunohistochemistry confirmed protein expression in the majority of cases. The expression of MMP12 was most abundant in multi-system LCH, which is the LCH type with the worst prognosis. This suggests that expression of MMP12 may play a role in the progression of LCH. These data reveal new insight into the pathology of LCH and provide new starting points for further investigation of this clonal proliferative disorder.     

Vitamin D differentially regulates B7.1 and B7.2 expression on human peripheral blood monocytes.

The hormonal active form of vitamin D3, 1,25-dihydroxyvitamin D3 (1, 25(OH)2D3), inhibits (through an unknown mechanism) the ability of monocytes/macrophages to induce T-cell activation. For T cells to be optimally activated, recognition of antigen/major histocompatibility complexes (MHC) by the T-cell receptor (TCR) must be accompanied by a second costimulatory signal. Considerable experimental data now suggest that this costimulatory signal is predominantly generated by B7.1 and/or B7.2 molecules, expressed on antigen-presenting cells (APC), when engaged to their counter-receptor, CD28, present on T cells. To determine whether the inhibitory effect of 1,25(OH)2D3 on monocytes/macrophages might involve modulation of the expression of B7.1 and B7.2 molecules, we analysed (by flow cytometry) the influence of 1,25(OH)2D3 and an analogue, KH 1060, on the expression of these two molecules at the surface of resting human peripheral blood monocytes. In parallel, we tested the effect of these two agents on human monocyte expression of cell-surface markers (CD14 and CD4) and antigen-presenting molecules (MHC class I and MHC class II). Our results showed that both 1,25(OH)2D3 and KH 1060 inhibited the basal expression of B7.2 in a dose- and time-dependent manner, without affecting B7.1. Moreover, these two compounds increased CD14 and reduced MHC class II and CD4 expression. Furthermore, the effect of 1,25(OH)2D3 on B7 molecule expression in combination with lipopolysaccharide (LPS) or cytokines, including interleukin-10 (IL-10), interferon-gamma (IFN-gamma) and tumour necrosis factor-alpha (TNF-alpha), was studied. The 1,25(OH)2D3-induced B7.2 down-regulation was still detectable when monocytes were activated by IL-10, IFN-gamma and TNF-alpha but not with LPS. Moreover, the induction of B7.1 by TNF-alpha was inhibited by addition of 1, 25(OH)2D3. We conclude that the ability of 1,25(OH)2D3 to decrease B7.2 expression on human monocytes might contribute to its inhibitory effect on APC-dependent T-cell activation and to its immunosuppressive properties observed in autoimmune diseases and organ transplantation.     

Pancreatic expression of B7 co-stimulatory molecules in the non-obese diabetic mouse

Expression of the co-stimulatory molecule B7-1 (CD80) on pancreaticß cells can overcome peripheral T cell tolerance Intransgenic models of autoimmune disease. This study aimed todetermine if aberrant B7-1 or B7-2 (CD86) expression on pancreaticß cells is involved in the pathogenesis of autoimmunediabetes in non-obese diabetic (NOD) mice. Immunohistochemlcalanalysis of NOD pancreas sections revealed no evidence of B7-1or B7-2 expression on pancreatic ß cells at any stageprior to the onset of either spontaneously arising or cyclophosphamldeaccelerateddiabetes. Likewise, the NOD-derived NIT-1 ß cell linedid not express surface B7 orB7-1 mRNA either constitutivelyor following exposure to IFN- and TNF-, two cytokines knownto be present in the Insulitis lesion of NOD mice, or cAMP whichcan induce B7-1 expression on B cells. Both B7-1 and B7-2 were,however, highly expressed on the majority of islet-infiltratinginflammatory cells in NOD mice between days 7 and 12 after theadministration of cyclophosphamide which results in acceleratedß cell destruction. Likewise B7-1 and B7-2 were extensivelyexpressed on islet-infiltrating cells present at the time ofdiabetes onset in NOD SCID mice with adoptively transferreddiabetes. By immunohistochemistry and flow cytometry, it wasdetermined that the phenotype of B7⁺ cells in the pancreas ofNOD mice 9 days after cyclophosphamide included a mixture ofmacrophages and both CD4⁺ and CD8⁺ T cells. B7-2 was also expressedon islet-infiltrating cells in the spontaneously occurring diabetesof female NOD mice, but the levels of B7-1 expression were lowin comparison with the accelerated models of diabetes. RIP-IL-2transgenic mice, which have extensive islet infiltration butno autoimmune ß cell destruction, also had virtuallyno B7-1 expression and a minority of B7-2-expressing inflammatorycells. Thus, the activation of ß cell-specific T cellsin NOD mice does not appear to be a result of aberrant expressionof B7 on the ß cells. Expression of B7-1 and B7-2on islet-infiltrating cells is, however, associated with autoimmuneß cell destruction, suggesting a role for the B7-CD28interaction in this process.     

B7.1、GM-CSF基因修饰的EL- 4细胞激发小鼠抗淋巴瘤免疫反应

目的 研究B7.1，GM-CSF基因修饰的淋巴瘤瘤苗进行恶性淋巴瘤免疫基因治疗的有效性。方法 用逆转录病毒载体分别将B7.1和GM-CSF基因导入小鼠淋巴瘤细胞EL-4中，得到EL-4/B7和EL-4/GM转基因瘤苗细胞，观察EL-4/B7和EL-4/GM瘤苗细胞对荷淋巴瘤小鼠的免疫治疗作用，以及预先接种过EL-4/B7或/和EL-4/GM瘤苗的小鼠，对野生型EL-4细胞致瘤性作用的影响，并检测接种EL-4/B7或/和EL-4/GM瘤苗的小鼠血浆IL-2及TNF-α的水平，及其脾淋巴细胞对野生型EL-4的细胞毒效应，另外，检测经EL-4/B7，EL-4/GM刺激后的小鼠脾淋巴细胞的增殖程度，结果 （1）经EL-4/B7、EL-4/GM细胞注射后，荷瘤小鼠的淋巴瘤生长速度变慢，生存时间延长，淋巴瘤组织中出现大量的炎症细胞；（2）接种一定数量的EL-4/B7，EL-4/GM细胞的小鼠，能抵抗野生型EL-4细胞的攻击；（3）接种瘤苗的小鼠血浆IL-2的水平明显升高，而TNF-α的水平无明显变化；（4）接种瘤苗的小鼠脾淋巴细胞，对野生型EL-4细胞有明显的细胞毒效应；EL-4/B7、EL-4/GM细胞能刺激小鼠脾淋巴细胞明显增殖。结论 B7.1,GM-CSF基因修饰的EL-4细胞，能有效地激发C57BL/6小鼠的抗淋巴瘤免疫反应，且B7.1基因与GM-CSF基因具有协同作用。     

The characteristic expression of B7-associated proteins in Langerhans cell sarcoma

Langerhans cell sarcoma (LCS) is a rare malignancy derived from dendritic cells of the epidermis that is characterized by cytological atypia, frequent mitoses, and aggressive clinical behavior. Cancer-associated B7 molecules including B7-H1, B7-DC, B7-H3 and B7-H4 are thought to be involved in the immunoescape of cancer cells and to function as prognostic markers. However, the expression and distribution of these molecules in LCS have not been described. Here we report that all of these molecules were observed in LCS sample sections by immunohistochemistry analysis. At the cellular level, they were found on the cell membrane and in the cytoplasm. Fluorescence dual staining indicated that B7-H1, B7-H3 and B7-H4 were principally associated with Langerin⁺ tumor cells. More interestingly, B7-H1, B7-H3 and B7-H4 were co-expressed on the same tumor cells. Z39Ig, the novel B7-related protein, was also found in the LCS sample sections. Fluorescence dual staining showed that Z39Ig was restricted on CD68⁺ macrophages. Our results suggest that B7-H1, B7-H3 and B7-H4 may be potential biomarkers to identify LCS, and a clear understanding of their functional roles may further elucidate the pathogenesis of this carcinoma and potentially contribute to the development of novel immunotherapeutic strategies.     

Tumor cells cotransfected with interleukin-7 and B7.1 genes induce CD25 and CD28 on tumor-infiltrating T lymphocytes and are strong vaccines

Interleukin-7 (IL-7) and the membrane molecule B7 are both able to provide proliferation and activation signals for T cells. However, tumor cells transfected to express either molecule alone are not reliably rejected in syngeneic hosts or are not sufficiently immunogenic to serve as potent tumor vaccines. Since IL-7 and B7 have shown synergistically to induce activation and proliferation of T cells in vitro, we have expressed B7.1 by means of a retrovirus in the mammary adenocarcinoma TS/A which arose spontaneously in a BALB/c mouse and in the plasmacytoma J558L and their IL-7-transfected sublines to improve vaccine efficacy. Expression of IL-7 or B7.1 alone in tumor cells decreased tumorigenicity, but nevertheless tumors grew in a substantial number of mice. In contrast, IL-7/B7.1 cotransfected cells did not grow as tumor in a single case. This inhibition of tumor growth was completely T cell dependent, because TS/A-IL-7/B7.1 cells retained their full tumorigenic potential in T cell-deficient mice. Analysis of tumor-infiltrating T lymphocytes revealed increased numbers of T cells in B7, IL-7 and IL-7/B7 transfected compared to parental tumors. In IL-7/B7 transfected tumors, T cell numbers were not further increased compared to that in singlegene-transfected tumors. However, T cells in B7 and IL-7 transfected tumors differed phenotypically with respect to activation markers. In B7 transfected tumors, T cells were predominantly CD28⁺ and CD25⁺, while in IL-7-transfected tumors, T cells were mainly CD28^? and CD25⁺. In IL-7/B7 cotransfected tumors, the majority of T cells was CD28⁺ and CD25⁺. Thus, IL-7 and B7 induced an anti-tumor immune response by complementary T cell directed pathways in a cooperative fashion. Importantly, immunization of mice with the transfected cells and subsequent contralateral challenge with parental tumor cells showed that IL-7/B7 co-expressing cells induced the most strongly protective immunity, which is superior to that induced by single-gene transfectants and to the adjuvant Corynebacterium parvum. Vaccine efficacy was abrogated when irradiated cells were used for vaccination. Together, our results show that IL-7 and B7.1 transfected tumor cells induce strong T cell activation and tumor immunity.     

Up-regulation of human epidermal Langerhans' cell B7-1 and B7-2 co-stimulatory molecules in vivo by solar-simulating irradiation

Ultraviolet (UV) radiation impairs cutaneous immune functions and induces antigen-specific tolerance both locally at the irradiated skin site, as well as at distant skin sites and systemically. It has been postulated that in the local model, altered Langerhans' cells (LC) provide tolerogenic signals, and studies in vitro have indicated that UV radiation may down-regulate the expression of co-stimulatory molecules on the surface of these cells. To examine the effect of UV radiation on LC co-stimulatory molecules in vivo, we irradiated human volunteers with erythematogenic doses of solar-simulating UV radiation (SSR), and analyzed the expression of cell surface markers in dermatome skin samples obtained 1–72 h post-irradiation. For flow cytometric analysis, epidermal cell (EC) suspensions were prepared and double labeled with monoclonal antibodies against CD1a or HLA-DR, and B7-1 (CD80), B7-2 (CD86), ICAM-1 (CD54), ICAM-3 (CD50), LFA-3 (CD58), E-cadherin, or integrin-β₄ (CD104). In unirradiated control skin samples, keratinocytes (KC) expressed high levels of E-cadherin. LC expressed high levels of both E-cadherin and ICAM-3, and low levels of B7-2, LFA-3, ICAM-1, and integrin-β₄. Following SSR, a triphasic reaction pattern was seen: an immediate, down-regulatory phase prevailing 2–6 h post-irradiation, when the number of DR⁺ and CD1a⁺ cells were temporarily reduced; a delayed, up-regulatory phase in which the number of LC was increased and the expression intensities of CD1a, HLA-DR, B7-1, and B7-2 were strongly up-regulated, maximally evident 12–24 h after irradiation, but no more seen at 48 h; and a late phase at 72 h, in which an influx of monocytes and a concomitant rise in DR⁺ cells was recorded. We conclude that to understand real-life cutaneous UV immunology, studies in vitro need to be complemented with studies in vivo. In the case of LC, the effects of erythematogenic UV radiation in vivo on human LC B7 co-stimulatory molecules include an up-regulatory stage.     

Reciprocal expression of co-stimulatory molecules,B7-1 and B7-2, on murine T cells following activation

The co-stimulatory B7 molecules (B7-1 and B7-2) are expressed on professional antigen-presenting cells in mice. In this study, we demonstrate that B7-1 (CD80) and B7-2 (CD86) are also expressed on murine T cells in the absence of major histocompatibility complex class II molecules. The temporal expression of these two molecules on T cells varies with the state of activation where resting T cells express B7-2 but show little or no expression of B7-1. Following activation, B7-2 expression is down-regulated and there is a concomitant increase in the expression of B7-1 on the cell surface which peaks at about 72 h. Thus these two co-stimulatory molecules are reciprocally expressed on the T cell surface. This pattern of expression of B7-1 and B7-2 on T cells suggests that these two molecules may have different roles in the generation and regulation of immune responses.     

The modulation of B7.2 and B7.1 on B cells by immunosuppressive agents.

Several recent studies demonstrate that B7.2, but not B7.1, play an important role in allergic inflammation and IgE production. Agents that down-regulate B7.2 may therefore be of benefit for the treatment of Th2-driven allergic diseases. Our current study was carried out to investigate the effect of immunosuppressive agents, cyclosporin A (CsA) and dexamethasone, on B7.2 and B7.1 expression on B cells stimulated with the superantigen, toxic shock syndrome toxin-1 (TSST-1). The analysis of B7.2 and B7.1 on the same cells by flow cytometry demonstrated that TSST-1 up-regulated B7.2+B7.1- but not B7.1+B7.2- on B cells in a dose-dependent fashion. CsA and dexamethasone significantly down-regulated B7.2+B7.1- but up-regulated B7.2-B7.1+ B cells in the presence or absence of TSST-1 (100 ng/ml). Interestingly, the combination of CsA and dexamethasone was much more potent in the inhibition of B7.2 expression than either of these agents alone. As CD40 is known to up-regulate B7.2 expression on B cells, the mechanism of B7.2 down-regulation by CsA and dexamethasone was further studied by investigating the effect of these agents on CD40 expression on B cells. TSST-1 significantly increased CD40 expression on B cells. However, the addition of CsA or dexamethasone significantly down-regulated CD40 expression. Anti-CD40 MoAb significantly reversed the effects of CsA or dexamethasone on B7.2 and B7.1 expression, suggesting that T cell engagement of CD40 plays a role in the mechanisms by which CsA and dexamethasone acts on B cells. These data demonstrate the modulatory effect of CsA and dexamethasone on B7.2 and B7.1 expression on B cells and the potential role of CD40 in mediating this effect.     

IgD expression on B cells is more efficient than IgM but both receptors are functionally equivalent in up-regulation CD80/CD86 co-stimulatory molecules

The expression and function of IgM and IgD antigen receptors were studied in a series of anti-hen egg lysozyme (HEL) immunoglobulin (Ig)-transgenic mice expressing either IgM alone, IgD alone, or both IgM and IgD. B cell surface expression of IgD was found to be more efficient than that of IgM. Thus antigen receptor density on IgD⁺, IgM^? B cells was twofold higher than on IgM⁺, IgD^? B cells despite the presence of sevenfold lower levels of membrane heavy chain mRNA, and coexpression of IgD with IgM led to almost complete inhibition of surface IgM. In addition, less extensive down-regulation of IgD occurred following exposure to antigen in vitro. When regulation of CD80/CD86 co-stimulatory molecules by surface Ig was examined, up-regulation of the former was initiated at lower antigen concentrations on IgM^?, IgD⁺ compared to IgM⁺, IgD^? B cells. On correcting for antigen receptor density, however, induction of CD80/CD86 by IgM and IgD was comparable. Taken together, these results reinforced the functional similarity of IgM and IgD antigen receptors while at the same time revealing differences in expression which may explain their simultaneous presence on mature B cells.     

Expression and function of the costimulatory molecule B7 on murine Langerhans cells: Evidence for an alternative CTLA-4 ligand

We have previously shown, through transfection experiments, that the murine B7 (mB7) molecule, a ligand for the CD28 and CTLA-4 receptors, is a sufficient costimulatory signal for the antigen-specific and major histocompatibility complex (MHC)-restricted activation of murine CD4⁺ T lymphocytes. In addition to mB7, another ligand with affinity for CTLA-4 has been described on spleen cells. Here we report our studies on the expression and function of these molecules on murine Langerhans cells (LC). Both anti-mB7 monoclonal antibody (mAb) 16-10A1 and human CTLA4Ig (hCTLA4Ig), a chimeric fusion protein consisting of the extracellular domain of human CLTA-4 and the constant domain of human IgG1, detected antigens(s) on cultured but not freshly isolated LC. Preincubation of cultured LC with anti-mB7 mAb did not significantly affect binding of hCTLA4Ig to these cells. This result demonstrate the existence of at least one other ligand for the CLTA-4 receptor on cultured LC. Functional studies revealed that the costimulatory activity of LC was inhibited better by hCTLA4Ig than by the anti-mB7 mAb. This differential effect was seen in the case of both alloreactive and antigen-specific, syngeneic T cell responses. These findings suggest that the non-mB7-ligand for CTLA-4 is functional and participates in the induction of immune responses by LC. Importantly, even synergistic combinations of anti-mB7 mAb and hCTLA4Ig did not inhibit completely the activity of LC. These findings therefore raise the possibility that LC express other costimulatory ligands besides mB7 and related family members.     

中波紫外线对皮肤免疫细胞的作用研究

紫外线诱导皮肤免疫抑制一直是光学免疫领域的研究热点,而中波紫外线(UVB)是引起皮肤免疫抑制作用的主要光谱,其对皮肤免疫细胞的作用是紫外线诱导皮肤免疫抑制的关键,皮肤中主要的免疫细胞大致也可分为固有免疫细胞和非固有免疫细胞,固有免疫细胞包括皮肤朗格汉斯细胞(LC)、肥大细胞、单核巨噬细胞、角质形成细胞(KC)、NK细胞;非固有免疫细胞主要包括T淋巴细胞、B淋巴细胞.研究UVB对皮肤固有免疫细胞和非固有免疫细胞的影响很有意义.