TLR的结构与功能及其肝癌免疫应答的研究进展

Toll样受体(TLR)主要位于免疫细胞表面,由胞外区、跨膜区和胞内区3部分组成,是模式识别受体家族之一。已发现的TLR家族成员共有12种,参与病原体及其产物等特异性配体的识别与信号转导,这可在病原体入侵机体的早期启动机体固有免疫应答,并诱导机体产生获得性免疫,从而清除入侵的病原体。此外,TLR与肝癌的发生、发展、转移有密切关系。本文综述了TLR的结构、分类、分布、功能以及其与肝癌的关系。     

EGFR抑制剂细胞磷酸化筛选模型的建立与应用

<正>表皮生长因子受体(EGFR)是一种具有酪氨酸激酶(PTK)活性的跨膜糖蛋白受体,由N端胞外区、跨膜区胞内区3部分组成,胞内区共542个氨基酸残基,由近膜区、酪氨酸激酶区、C末端等3个亚区构成,近膜区的前13个氨基酸(645~657)介导胞内二聚化[1]。自身磷酸化位点位于C末端,其中Tyr1068为最主要的3个磷酸化位点(Tyr1068、Tyr1148和Tyr1173)之一,与细胞信号传     

抗癌胚抗原嵌合抗体在秋粘虫细胞中的重组与表达

经同源重组构建了同时含抗癌胚抗原（ＣＥＡ）嵌合抗体重、轻链基因的双重组病毒ＢａｃＣｈＨＬ２５。利用双重感染和双重组病毒感染秋粘虫（Ｓｆ９）细胞，免疫杂交结果显示嵌合抗体重、轻链同时在胞内得到了表达，并且两种情况均能在胞内组装成完整免疫球蛋白四聚体分子。ＲＩＡ和ＥＬＩＳＡ检测证明嵌合抗体与亲本鼠源单抗Ｅ７Ｂ１０具有相似的结合抗原ＣＥＡ的能力。     

嵌合免疫受体活性的体外检测

目的:体外检测嵌合免疫受体3(CIR3)的活性,为肿瘤的过继免疫治疗提供可靠依据。方法:将已经构建好的CIR3通过电穿孔法转染人T淋巴细胞,检测其在T淋巴细胞的表达及与CEA阳性胃癌细胞株MKN-45的结合情况和IL-2产生情况。结果:CIR3成功转染并表达在T细胞的表面,转染CIR3的T细胞体外能够识别胃癌细胞株MKN-45并与之结合形成典型的花环结构,受CEA刺激后能产生细胞因子IL-2。结论:表达在T淋巴细胞表面的CIR3能够有效结合肿瘤细胞并不受MHC的限制,受CEA刺激后能产生细胞因子IL-2,为下一步的体内实验提供可靠依据。     

NOD2、RIP2和IRF5在针对结核分支杆菌I型干扰素应答中起关键作用

细胞一般通过表面Toll样受体识别细菌感染,当细菌产物突破细胞膜后,细胞胞浆也能起免疫监视作用。细菌被胞质内受体识别后刺激细胞产生干扰素IFNα和IFNβ,这些干扰素是针对细菌,病毒的关键免疫中介。类似于许多细胞内病原体,     

细胞内模式识别受体研究进展

天然免疫系统要依赖模式识别受体识别人侵的外源病原微生物,然后将其清除.哺乳动物主要具有两类微生物识别系统,一类是膜结合受体,如Toll样受体,可识别胞外微生物,然后活化细胞内信号来激发机体的免疫反应;另一类是细胞内的模式识别受体,包括NOD样受体和具有螺旋酶结构域的抗病毒蛋白RIG-1和MDA5.这些胞浆分子可识别病原微生物、非微生物以及一些危险信号,在机体的健康与疾病中发挥着十分重要的作用.本文就细胞内天然免疫受体的种类和功能作一综述.     

Eph-ephrin双向信号功能的研究进展

产生促红细胞生成素的肝细胞(erythropoietinproducing hepatocyte,Eph)受体是众多的细胞表面型酪氨酸蛋白激体酶受体中的一种,是酪氨酸蛋白激酶受体家族中的最大成员.其配体主要表达于细胞表面,被命名为ephrin.Eph受体及其配体ephrin统称为Eph家族蛋白.Eph受体属跨膜蛋白,存在胞外配体结合区、跨膜区和胞内区.Eph胞内近细胞膜区域相对保守,包含1个具有酪氨酸残基的高度保守的近膜区结构域,紧接1个具酪氨酸激酶活性的结构域、SAM(sterile alpha motif)结构域和C端的PDZ结合序列.Eph的胞外结构包含1个球形的配体结合域(ligand binding domain,LBD)、1个临近的半胱氨酸富集区(cysteine-rich domain,CRD)以及2个Ⅲ型纤维连接蛋白重复区.其中CRD在Eph-ephrin信号复合体的形成过程中起到关键作用[1].所有ephrin均包含1个保守的胞外受体结合区.除此之外,ephrinA通过一个糖基磷脂酰肌醇(glycosylphosphatidylinositol,GPI)锚定于细胞膜上;ephrinB的结构包括跨膜区和胞质区,其中胞质区包含一小段高度保守的区域以及羧基端PDZ结构域的结合基序,这一PDZ结构域结合基序对于细胞定位及逆向信号起到重要作用.     

半乳糖凝集素3对树突状细胞及T淋巴细胞功能影响的研究进展

半乳糖凝集素3(Gal-3)是半乳糖凝集素家族成员之一,它是半乳糖凝集素家族中唯一的嵌合型凝集素,存在于正常细胞和肿瘤细胞的胞核、胞质和细胞外基质中,能调节树突状细胞(DC)和T淋巴细胞的免疫功能,调节机体免疫应答和炎症反应。研究发现DC分泌Gal-3具有抑制自身凋亡、调节细胞因子生成以及调节T细胞应答等多种功能。同时Gal-3位于胞外和胞内对T淋巴细胞分别具有相反作用,胞外Gal-3诱导T细胞凋亡,胞内Gal-3抑制其凋亡。此外Gal-3在调节炎症反应中的起重要作用。     

FGF10、FGF18及其受体在小鼠卵巢内的定位分布

目的观察成纤维细胞生长因子(FGF10、FGF18)及其受体FGFR1、FGFR2和FGFR3在昆明(KM)小鼠卵巢内的定位与分布。方法应用免疫组织化学法进行定位观察。结果FGF10及其受体FGFR1与FGFR2的免疫阳性反应见于卵母细胞的胞质,此外,FGFR2的阳性反应还见于卵泡膜。卵母细胞和黄体细胞的胞质呈FGF18免疫阳性反应,FGFR3的免疫阳性反应物位于卵母细胞、卵泡细胞和黄体细胞的胞核。结论FGF10、FGF18及其受体在KM小鼠卵巢的分布,可能参与卵泡的生长发育和卵母细胞的成熟。     

Toll样受体与配体复合物结构的研究进展

Toll样受体(TLR)是一类模式识别受体,通过识别病原微生物的保守结构分子模式,触发先天免疫反应和基本的抗原特异适应性免疫。一些TLR结合配体复合物及胞内外结构域的晶体结构已经通过X射线晶体衍射分析确定。尽管配体结合位点各有不同,但是TLR家族胞外结构域均为马蹄状结构,其配体复合物的"m"外形也极度相似,C末端中心汇聚对胞内Toll/白细胞介素1受体(TIR)结构域紧靠一起非常重要,是启动下游信号的必需步骤。本文主要总结了TLR胞内外功能结构域及配体复合物的结构。     

Anti-citrullinated Protein Antibodies Activated ERK1/2 and JNK Mitogen-activated Protein Kinases via Binding to Surface-expressed Citrullinated GRP78 on Mononuclear Cells

In a previous study, we found that anti-citrullinated protein antibodies (ACPAs) enhance nuclear factor (NF)-κB activity and tumor necrosis factor (TNF)-α production by normal human peripheral blood mononuclear cells (PBMCs) and U937 cells via binding to surface-expressed citrullinated glucose-regulated protein 78 (cit-GRP78). However, the downstream signaling pathways remain unclear after binding. In the present study, we firstly measured the effects of different kinase inhibitors on ACPA-mediated TNF-α production from normal PBMCs and monocytes. Then, the native and phosphorylated mitogen-activated protein kinases (MAPKs) were detected in ACPA-activated U937 cells by Western blotting. We also explored the role of the phosphoinositide 3-kinase (PI3K)-Akt pathway in activating IκB kinase alpha (IKK-α) in ACPA-stimulated U937 cells. Finally, we measured the amount of cit-GRP78 from PBMC membrane extracts in RA patients and controls. We found that MAPK and Akt inhibitors, but not PI3K inhibitor, remarkably suppressed ACPA-mediated TNF-α production. Interestingly, ACPAs selectively activated extracellular signal-regulated kinase 1/2 (ERK1/2) and c-jun N-terminal kinase (JNK), but not p38 MAPK, in U937 cells. This activation was suppressed by cit-GRP78, but not GRP78. The JNK activation further enhanced the phosphorylation of Akt and IKK-α. The expression of cit-GRP78 on cell membrane was higher in RA than normal PBMCs. Taken together; these results suggest that through binding to surface, over-expressed cit-GRP78 on RA PBMCs, ACPAs selectively activate ERK1/2 and JNK signaling pathways to enhance IKK-α phosphorylation, which leads to the activation of NF-κB and the production of TNF-α .     

Dopamine promotes the progression of AML via activating NLRP3 inflammasome and IL-1β

Mental stress has been shown to activate sympathetic adrenergic system to produce dopamine and finally promote the progression of cancer. Dopamine can also regulate the immune system through secreting kinds of cytokines. However, what role does dopamine play in acute myeloid leukemia (AML) remains unclear. Here, we investigated the effects and mechanisms of dopamine in NLRP3 inflammasome activation and cellular viability of acute myeloid leukemia U937 cells. Our results showed that dopamine enhanced the viability of U937 cells and activated the NLRP3 inflammasome in U937 cells. To further explore the mechanism of dopamine on U937 cells, we examined the expression level of dopamine receptors (DRs). We found that the mRNA expression level of DR5 in U937 cells was significantly higher than other dopamine receptors. Furthermore, we treated U937 cells with DR1/2/3/5 antagonist before dopamine, and it manifestly reversed the NLRP3 inflammasome activation and the viability-enhancing effect in U937 cells induced by dopamine. Anti-IL-1β antibody also could partly reversed the viability-enhancing effect by dopamine. We concluded that dopamine could enhance the viability of U937 cells through DR1/5 receptor pathway and activate NLRP3 inflammasome.     

A new tumor-specific variant of GRP78 as target for antibody-based therapy

The chaperone GRP78 is a member of the heat-shock protein 70 (HSP70) family and is responsible for cellular homeostasis by preventing stress-induced apoptosis. GRP78 is expressed in all cells of the body. In malignant cells, which are permanently exposed to environmental stress, GRP78 is overexpressed and increased levels can be found in the cytoplasm and on the cell membrane. Thus, GRP78 promotes tumor proliferation, survival, metastases and resistance to a wide variety of therapies. Like other tumor-specific membrane molecules, GRP78 can also be present on cancer cells in a variant form. This modification qualifies it as a target for immune surveillance and antibody responses. The fully human monoclonal IgM antibody, SAM-6, was isolated from a gastric cancer patient and it binds to a new variant of GRP78 with a molecular weight of 82 kDa. The epitope is an O-linked carbohydrate moiety and is specific for malignant cells. These data show that cancer-specific modifications of cell-surface protection molecules are (a) subject of an immune response and (b) ideal targets for new therapeutical approaches.     

Binding and catabolism of aggregated immunoglobulins bearing C3b or iC3b by U937 cells.

Mononuclear cells play an important role in the elimination of immune complexes (IC). In the presence of complement (C) the binding and degradation of IC by mononuclear cells is enhanced at least two-fold. The enhancement of binding is caused by a synergistic interaction of the IC with cellular Fc and complement receptors (R). In the present study we have investigated the contribution of the complement receptors CR1 and CR3 of human monocyte cell line U937 on the complement-mediated binding and degradation of immune complexes and soluble aggregates of IgG (AIgG) bearing C3b or iC3b. It was found that deposition of C3b on AIgG enhanced the binding of AIgG to U937 cells at least two-fold. The C3b-mediated enhancement of binding was abolished by anti-CR1. iC3b-bound to AIgG also enhanced the binding of AIgG to the cells. This binding was only partially reduced by anti-CR3 antibodies, but the combination of anti-CR1 and anti-CR3 fully abolished the iC3b-mediated enhancement of binding. These results suggest that both CR1 and CR3 contribute to the complement-mediated binding and degradation of soluble IC by mononuclear phagocytes.     

Human immunodeficiency virus infection of monocytic and T-lymphocytic cells: Receptor modulation and differentiation induced by phorbol ester

The monocytic leukemic cell line U937 can be infected with human immunodeficiency virus type 1 (HIV-1) to become permanently infected virus producers. Uninfected U937 cells express T4 (CD4) antigen and form syncytia when mixed with HIV-1 producing cells. Anti-T4 monoclonal antibodies block syncytium formation indicating that the HIV-1 receptors on U937 cells include T4 antigen. The promyelocytic leukemic cell line HL60, while expressing only low amounts of surface T4 and not forming syncytia on exposure to HIV-1, can be infected by HIV-1 at lower efficiency than U937 and T-cell lines. 12-O-Tetradecanoylphorbol-13-acetate (TPA) treatment induces the differentiation of U937 cells into macrophages. HIV-infected U937 cells retain the ability to differentiate, though less efficiently, as shown by the appearance of monocyte/macrophage surface markers. T4 antigen on both U937 and T-cell lines is down regulated by TPA treatment. Functional receptors for HIV-1, assayed by syncytium induction and pseudotype plating, are lost concomitantly with T4 antigen following TPA treatment of U937 cells and T cells.     

Dibutyryl cyclic AMP stimulation of a monocyte-like cell line, U937: a model for monocyte chemotaxis and Fc receptor-related functions.

Treatment of the U937 cell line with 1 mM dibutyryl cyclic AMP (Bt2cAMP) resulted in a reduction in cell size and inhibition of DNA synthesis, and morphologically the cells appeared similar to macrophages. Electron micrographs indicated an increase in intracellular apparatus, whilst histochemical studies revealed smaller, denser nuclei and a greater intensity of non-specific esterase staining. Ia-like antigens (HLA-DR and HLA-DC) and complement receptor CR1 were not detected on U937 cells by monoclonal antibodies, nor were they induced by Bt2cAMP. CR3 was present in small amounts on U937 cells, and stimulation with Bt2cAMP increased the expression of this molecule in the cytoplasm and on the cell surface. Leu M3, a monocyte-specific antibody, was weakly reactive on both unstimulated and stimulated cells, whereas transferrin receptors, present on 90% of U937 cells, were lost after 48-hr stimulation with Bt2cAMP. JW6 and NH6, two monoclonal antibodies raised in our laboratory and found to be against immature monocytic antigens, showed decreased expression on stimulation. Monomer IgG binding via Fc receptors decreased on stimulated cells, and a monoclonal antibody (32.2) specific for FcRI confirmed this to be due to a decrease in the number of high-affinity receptors, rather than a decrease in IgG-binding affinity. In contrast, expression of the low-affinity FcRII, monitored by monoclonal antibody IV3, increased dramatically after stimulation. Other functional changes included the production of superoxide anions and the induction of non-specific phagocytosis. Two dimensional gel analysis, of detergent soluble proteins from unstimulated and 48-hr stimulated U937 cells, showed many differences in protein expression. A detailed investigation of these changes will facilitate a better understanding of the molecular mechanisms involved in the differentiation of U937 cells.     

The immunosuppressive and protective ability of glucose-regulated protein 78 for improvement of alloimmunity in beta cell transplantation

An insulinoma cell line, NIT-1, transfected with glucose-regulated protein 78 (GRP78) was established, namely NIT-GRP78, and used to study the immunosuppressive and protective ability of GRP78. In extended cytotoxic T lymphocyte (CTL) killing assay, NIT-1-primed lymphocytes were more cytotoxic in killing beta cells than NIT-GRP78-primed lymphocytes. Severe necrosis was observed only when the NIT-1-primed lymphocytes were cultured with NIT-1 beta cells, but not with NIT-GRP78 cells. In addition, an increase of interleukin (IL)-4 secretion from beta cell-primed splenocytes when GRP78 presence was observed in cytokine enzyme-linked immunosorbent assay (ELISA). Diabetic mice reached normoglycaemia promptly and gained weight after transplantation of either NIT-1 or NIT-GRP78 cells. However, the recipient mice transplanted with NIT-GRP78 cells lived much longer than those recipients transplanted with NIT-1 cells, which was due apparently to prolonged insulin production by the transplanted NIT-GRP78 cells. In fact, we observed a significant increase of insulin concentration after glucose stimulation of diabetic mice received NIT-GRP78 cells at day 7 post-transplantation. From the results we propose that GRP78 could have a dual function in both protecting NIT-1 cells from CTL-mediated lysis and stimulating a population of T helper 2 cells to down-regulate the immune response to the transplanted beta cells.     

Up-regulation of gamma interferon receptors on the human monocytic cell line U937 by 1,25-dihydroxyvitamin D3 and granulocyte-macrophage colony stimulating factor

The human monoblast-like cell line U937 can be induced to differentiate by a variety of agents including phorbol esters, retinoic acid, gamma interferon (IFN gamma), and 1,25-dihydroxyvitamin D3 (VD3). Increased expression of OKM1 antigen, Fc receptors, and other cell surface antigens occur with the differentiation of this cell line along the macrophage lineage. Whereas 10(-8) M VD3 alone induces changes in cell surface antigens, there were no changes in the number or affinity of IFN gamma receptors. Incubation of U937 with VD3 and 100 U/ml of granulocyte-macrophage colony-stimulating factor (GM-CSF) resulted in further increases in OKM1 antigen expression and an up-regulation of IFN gamma receptors. The number of IFN gamma receptors increased between two- and fourfold and was maximal after 48 h incubation with VD3 and GM-CSF. Scatchard analysis revealed a single class of receptors before or after differentiation, although the increase in receptor number was associated with an overall decrease in receptor-binding affinity. Incubation of U937 with VD3 plus GM-CSF and IFN gamma resulted in further increases in the density of OKM1 antigen expressed per cell. This increase in OKM1 expression was greater than that observed for U937 incubated with VD3 and GM-CSF or VD3 and IFN gamma alone. These results suggest that GM-CSF up-regulates IFN gamma receptors on VD3-stimulated U937 and enables these cells to be induced further along the pathway of macrophage differentiation, possibly by subsequent interaction with additional cytokines such as IFN gamma.     

Interactions of promonocytic U937 cells with proteins of the extracellular matrix.

Monocyte interaction with proteins of the extracellular matrix (ECM) is regulated by expression of specific cell-surface receptors. 12-O-tetradecanoyl phorbol-13-acetate (TPA) has been shown to induce the promonocytic cell line U937 to a more differentiated monocyte-like state. In this study we have analysed the attachment of U937 cells to ECM proteins and the effects of treatment with TPA on this process. Non-induced U937 cells attach to fibronectin- and Matrigel-coated surfaces without TPA stimulation, but TPA further increases adherence to these substrates as measured by an enhanced binding and by the lower concentration of proteins needed in the substrate to achieve 50% of maximal cell adhesion. Attachment to type I collagen was seen only with activated U937 cells, whereas no measurable attachment to bovine serum albumin, vitronectin, and type IV collagen was detected. TPA-activated U937 cells showed a two-fold increase in the expression of the RGD-dependent integrin receptors alpha 3 and alpha 5, and a reduction in the expression of alpha 4, another fibronectin-specific receptor, whereas the common beta 1 chain was unchanged. Attachment of U937 cells to fibronectin was primarily mediated by the alpha 3 and alpha 5 integrins, as revealed by the ability of GRGDS peptides to inhibit attachment, whereas the CS-1 peptide, containing the alpha 4 binding site, was largely ineffective in blocking attachment.     

Purification of type I and type II tumor necrosis factor receptors from human lung tissue.

Two receptors for tumor necrosis factor-alpha (TNF) were purified from detergent-solubilized human lung tissues by adsorption to TNF-Sepharose, followed by elution with low pH. By SDS-PAGE analysis, the two proteins had molecular weights of 75 and 55 kD. Using a soluble receptor assay, a binding affinity of approximately 1.2 nM was calculated for the isolated lung receptors. Each protein, isolated by electroelution from polyacrylamide gels, specifically bound TNF. Antibodies raised against the mixture of type I and II receptors bound specifically to both purified receptors by immunoblot analysis. Both the 75- and 55-kD receptors could be precipitated from 125I-surface-labeled or 35S-methionine-labeled U937 cells using TNF-Sepharose or anti-receptor antibodies. In addition, the anti-TNF receptor antibodies partially blocked binding of TNF to U937 cells and specifically immunoprecipitated 125I-TNF cross-linked to its receptors on U937 cells. These results demonstrate that both type I and II TNF receptors can be isolated from human lung tissue by ligand affinity chromatography, and that U937 cells express both TNF receptor types.