旋毛虫钙网蛋白对补体甘露糖结合凝集素途径活化的影响?

为研究旋毛虫感染的致病机制,探讨旋毛虫钙网蛋白对补体凝集素途径活化的影响,本文首先通过ELISA和Far western blot方法检测重组旋毛虫钙网蛋白(recombinant Trichinella spiralis calreticulin,rTs-CRT)与甘露糖结合凝集素(mannose binding lectin,MBL)的相互作用情况,随后采用ELISA法研究rTs-CRT对血清中的MBL以及重组MBL分子与甘露糖的结合的抑制作用,最后,研究这种抑制效果是否会抑制补体凝聚素途径的活化。ELISA及Far western blot结果证实rTs-CRT可结合MBL分子,且二者的结合可抑制血清以及重组MBL分子结合甘露糖。同时,这种抑制作用会减弱补体凝集素途径活化后C4b的沉积。结果表明,rTs-CRT可通过结合补体MBL抑制其识别甘露糖,进而减弱补体凝集素途径的活化。     

湖北省汉族人群甘露糖结合凝集素基因启动子区多态性与SLE关联性的研究

甘露糖结合凝集素 (mannose bindinglectin ,MBL)是一种由肝脏合成和分泌的急性期蛋白 ,可激活补体 ,溶解病原菌〔1〕,并具有调理吞噬作用。是参与非特异性免疫防御的重要分子。MBL基因启动子区具有两个多态性位点 :H L( 5 5 0bp ,G C)和X Y( 2 2 1bp ,C G) ,可影响MBL基因的转录 ,降低血清中MBL的浓度。已证明启动子的单元型HY、LY、LX分别与血清中高、中、低水平的MBL相关〔2〕。系统性红斑狼疮 (SLE)的发病与抗原 抗体复合物的清除缺陷有关。由于MBL基因启动子区的多态性可影响MBL的基因转录及其在血清中的浓度 ,从而影…     

甘露聚糖结合凝集素的分离纯化及其与单糖配体的结合活性鉴定

从羊血清中分离纯化甘露聚糖结合凝集素 (MBL ) ,并研究其与单糖配体的结合活性 ,为进一步研究MBL与病原微生物的识别结合活性提供研究基础。用甘露聚糖 Sepharose 4B亲和柱行亲和层析 ,从羊血清中分离纯化出MBL分子 ,行还原性SDS PAGE测定其分子量。用VII型胶原酶鉴定其胶原样结构。用酶联凝集素试验 (ELLA)鉴定其与单糖配体的结合活性。得到纯化的羊血清MBL分子有两种单体 ,相对分子质量分别为 2 90 0 0和 330 0 0。羊血清MBL具有胶原样结构 ,可以被胶原酶消化。羊血清MBL与辣根过氧化物酶表面糖链中甘露糖的结合受N 乙酰葡糖胺、L 岩藻糖、D 氨基葡糖、N 乙酰氨基半乳糖不同程度的抑制。MBL与单糖配体的结合活性预示了其潜在的与表面富含这些糖基结构的病原微生物的识别结合能力。     

中国佤族人群MBL基因SNP及其单倍型与基因型的研究

甘露聚糖结合凝集素（mannan-binding lectin，MBL）通过激活补体凝集素途径和调理吞噬作用清除病原体及受感染细胞，在机体天然免疫中起关键作用。已发现MBL基因上存在至少20个单核苷酸多态性（SNP）位点，仅其中6个SNP位点对MBL血清水平有较大的影响，     

MBL基因不同单倍体型启动活性的差异研究

甘露糖结合凝集素（mannose-binding lectin，MBL）是Ca^2＋依赖型（C型）凝集素家族一员，是固有免疫系统的重要成员。血清MBL水平低下导致调理吞噬缺损，使机体易患感染性疾病，还可明显加重疾病的症状，影响病程和转归。     

甘露聚糖结合凝集素与临床疾病的研究进展北大核心CSCD

甘露聚糖结合凝集素(MBL)是天然免疫补体系统中的一员,主要由肝细胞合成,作为急性期反应蛋白分泌入血清。血清MBL的水平主要由MBL2基因启动子区及外显子1区的基因多态性决定。MBL可选择性的与病原微生物(如G+/G-细菌、病毒、真菌、原生物等)、坏死损伤细胞、凋亡细胞以及肿瘤细胞等表面的相应配体结合,通过激活补体系统、调理吞噬、调节炎症反应等保护人体。血清MBL的水平对人体影响较大:当血清MBL缺乏时,机体易患某些疾病,如感染性疾病、自身免疫性疾病;但如果血清MBL水平过高,又会对自身组织造成损伤,如在心肌梗死及器官移植中,引起机体的缺血再灌注损伤;此外,MBL基因型及血清MBL水平与肿瘤的易感性可能也存在一定关系。     

甘露聚糖结合凝集素与临床疾病的研究进展

甘露聚糖结合凝集素(MBL)是天然免疫补体系统中的一员,主要由肝细胞合成,作为急性期反应蛋白分泌入血清。血清MBL的水平主要由MBL2基因启动子区及外显子1区的基因多态性决定。MBL可选择性的与病原微生物(如G+/G-细菌、病毒、真菌、原生物等)、坏死损伤细胞、凋亡细胞以及肿瘤细胞等表面的相应配体结合,通过激活补体系统、调理吞噬、调节炎症反应等保护人体。血清MBL的水平对人体影响较大:当血清MBL缺乏时,机体易患某些疾病,如感染性疾病、自身免疫性疾病;但如果血清MBL水平过高,又会对自身组织造成损伤,如在心肌梗死及器官移植中,引起机体的缺血再灌注损伤;此外,MBL基因型及血清MBL水平与肿瘤的易感性可能也存在一定关系。     

甘露聚糖结合凝集素与妊娠期糖尿病的研究进展

甘露聚糖结合凝集素(mannose binding lectin,MBL)也曾称为甘露聚糖结合蛋白(mannan binding protein)是一种钙离子依赖的(C型)血清凝集素蛋白,也是第一个被发现的具有防御功能的C型凝集素。MBL作一种急性时相蛋白由肝脏合成分泌,是宿主体内非特异免疫最重要的免疫分子。一直以     

甘露糖结合凝集素缺失与自身免疫病

甘露糖结合凝集素又称甘露糖结合蛋白 (MBP) ,是Ca2 + 依赖型 (C 型 )动物凝集素家族一员。MBL可通过不同机制激活补体参与补体系统的经典与替代途径 ,又称凝集素途径。本文综述了近年来MBL结构与功能、MBL缺失等的研究进展 ,重点阐述了MBL缺失与自身免疫病的关系     

慢性丙型肝炎患者血浆内毒素和血清MBL变化及临床意义

目的:探讨了慢性丙型肝炎患者血浆内毒素和血清甘露聚糖结合凝集素(MBL)水平的变化及意义.方法:应用鲎试验和酶联法对31例慢性丙型肝炎患者进行了血浆内毒素和血清MBL测定,并与35名正常健康人作比较.结果:慢性丙型肝炎患者血浆内毒素和血清MBL水平均非常显著地高于正常人水平(P<0.01),且内毒素水平与MBL呈正相关...     

Deficiency of the mannan-binding lectin pathway of complement and poor outcome in cystic fibrosis: bacterial colonization may be decisive for a relationship

In cystic fibrosis (CF) prognosis concerning lung damage development is highly variable and difficult to predict. Mannan-binding lectin (MBL) deficiency has been reported to be associated with poor outcome in CF lung disease. MBL is a recognition molecule of the MBL pathway of the complement system and is encoded by a gene characterized by a high degree of polymorphism. Some genotypes result in low serum concentrations of MBL. MBL-associated serine protease 2 (MASP-2) is another protein belonging to the MBL pathway. A mutation resulting in low levels of MASP-2 in serum has been described recently. In the present study, 112 CF patients aged 4-54 years were investigated for MBL and MASP-2 genotypes, serum levels of MBL and MASP-2 and the MBL pathway function in serum. No correlation to reduced lung function or need for lung transplantation was seen, either for MBL deficiency, MASP-2 gene mutation or reduced MBL pathway function. However, in the 27 patients colonized with Staphylococcus aureus, MBL-deficient genotypes were associated with decreased lung function. As expected, MBL pathway function in serum was reduced both in MBL-deficient patients and in patients carrying a mutant MASP-2 allele. An unexpected finding was that CF patients had higher serum levels of MBL than healthy controls when corrected for MBL genotype. In conclusion, MBL pathway function was affected both by MBL and by MASP-2 genotypes. However, MBL or MASP-2 levels in serum did not affect the clinical outcome in the cohort of CF patients studied.     

High prevalence of mannose-binding lectin (MBL) deficiency in premature neonates

Mannose-binding lectin (MBL) is a component of innate immunity and thus particularly important in neonates in whom adaptive immunity is not yet completely developed. Promoter polymorphisms and structural exon-1 mutations in the MBL2 gene cause reduced or deficient MBL plasma concentrations. The aim of our study was to determine the prevalence of MBL deficiency in neonates admitted to the neonatal intensive care unit (NICU). Eighty-five NICU patients (69 premature) were included in the study. We measured MBL concentrations in umbilical cord and neonatal blood within 24 h after birth by ELISA technique. MBL2 genotypes (n = 67) were determined by Taqman analysis. MBL concentrations were measured longitudinally during three weeks in 26 premature neonates. The association between pre- and intra-partum clinical data and MBL concentrations was investigated. At birth, 29 (42%) premature and six (38%) term neonates had MBL plasma concentrations < or = 0.7 microg/ml which was regarded as deficient. Twenty-one (38%) premature and four (36%) term neonates had variant MBL2 haplotypes, corresponding to exon-1 mutations and the LXPA haplotype. MBL concentrations increased over time in neonates with wild-type MBL2 haplotypes, but not in neonates with variant haplotypes. Low MBL plasma concentrations were related to lower gestational age and variant MBL2 haplotypes. Umbilical cord and neonatal MBL plasma concentrations appeared to be similar. In conclusion, almost half of our NICU patients, especially the premature ones, were MBL-deficient at birth. These infants may be at increased risk of neonatal infections. MBL concentration can reliably be measured in umbilical cord blood and it is positively correlated with gestational and postnatal age.     

Evaluation and clinical interest of mannan binding lectin function in human plasma

The mannan binding lectin (MBL) plays a major role in innate immunity through its ability to activate complement upon binding to carbohydrate arrays on the surface of various microorganisms. The question of a possible association of the MBL structural gene polymorphism and the oligomeric state of MBL was poorly documented. For these reasons, it appears difficult to evaluate MBL in blood patients on the only basis of protein contents, even in combination with MBL genotyping. This study reports a method to calculate a specific activity for circulating MBL, that relies on: (i) the availability of purified MBL; and (ii) a simplified MBL activity assay based on complement activation. The three-step MBL purification from human plasma reported here is characterized by a highly purified MBL, that occurs in two different oligomeric forms. The results on the specific activity of these forms show that the higher oligomeric forms of MBL have the ability to induce C4 cleavage more efficiently than the corresponding lower oligomers. The usefulness of this approach is illustrated by its potential interest in the biological exploration of certain pathology, for example in the follow-up of chronic hepatitis C. Further investigation is needed to establish whether MBL specific activity (MBLsa) is correlated to the polymorphic state of the molecule. The relative simplicity of the test described here allows better investigation on the relationship between MBL biological activity and its genotype.     

Analysis of the relationship between mannose-binding lectin (MBL) genotype,MBL levels and function in an Australian blood donor population

The mannose-binding lectin (MBL) pathway of complement activation is an important component of innate host defence. Numerous studies have described associations between the MBL genotype, MBL levels and disease susceptibility. However, genotyping and quantitative assays used in these studies have frequently been limited, and comprehensive data examining the interaction between structural and coding MBL genetic variants, MBL antigenic levels and MBL functional activity are lacking. Such data may be important for accurate planning and interpretation of studies of MBL and disease. This study has examined MBL in a cohort of 236 Australian blood donors. Five MBL promoter and coding single nucleotide polymorphisms were genotyped using polymerase chain reaction-sequence-specific priming (PCR-SSP). Plasma levels of MBL antigen were quantified using a double-antibody enzyme-linked immunosorbent assay (ELISA), and functional MBL levels were quantified using a mannan-binding assay. Activation of the complement pathway by MBL was measured in a C4-deposition assay. Significant associations were found between both coding and promoter polymorphisms and MBL antigenic and functional levels. There was significant correlation between the results of MBL double-antibody, mannan-binding and C4-deposition assays. Comprehensive MBL genotyping and functional MBL quantitation using mannan-binding and C4-deposition assays have the potential to be highly informative in MBL disease association studies.     

Mannose-binding Lectin <Emphasis Type="Italic">MBL2</Emphasis> Gene Polymorphisms and Outcome of Hepatitis C Virus-infected Patients

INTRODUCTION: Mannose-binding lectin (MBL) is involved in host's response to several infections including hepatitis B but little is known about MBL and hepatitis C virus (HCV) infection. The present study attempts to investigate whether MBL2 genotype and serum MBL levels affect the course of HCV infection. RESULTS AND DISCUSSIONS: We investigated the variant alleles in MBL2 gene promoter and exon-1 regions in 80 Caucasian HCV-infected patients. Mutations in MBL2 were determined by polymerase chain reaction and restriction fragment length polymorphisms analysis. Serum MBL levels were measured by ELISA. Polymorphism homozygosity in exon-1 region was significantly related to lower serum MBL levels (p < 0.001), to liver inflammation (p = 0.034, OR = 11.7) and, in a lesser degree, to fibrosis. Polymorphisms in promoter sites -221nt and -550nt were not shown to be related with serum MBL levels or progress to liver inflammation and fibrosis. Serum MBL levels were adversely associated with progression to fibrosis (p = 0.037). Response to antiviral treatment was related to hepatitis C virus genotype (p < 0.001, OR = 10.9), but not to MBL2 genotype or serum MBL levels. CONCLUSION: These findings suggest that polymorphisms in MBL2 gene exon-1 region are related to low serum MBL levels and progression of HCV infection to liver inflammation and fibrosis.     

The 'involution' of mannose-binding lectin

Mannose-binding lectin (MBL) acts as a serum opsonin in innate immune defense and induces complement activation by the lectin pathway. In humans, low levels of functional serum MBL are caused by the dominant action of three single nucleotide substitutions in exon 1 that disrupt the glycine-rich backbone structure of the protein. The presence of common MBL variant alleles is associated with both infectious and autoimmune diseases. Conversely, it has also been suggested that MBL variants are maintained because of selective advantages for the host. In man, the MBL genetic system comprises one functional gene (MBL2) and one expressed pseudogene (MBL1P1), whereas the lower primate, the rhesus monkey resembles rodents with two functional MBL genes. We have investigated the molecular mechanisms behind the evolutionary loss of MBL expression from lower primates to man, including silencing of the MBL1P1 gene and the generation of MBL2 variant structural alleles and promoter polymorphisms leading to the present human MBL2 haplotypes. We present data showing that the MBL1P1 gene has been repeatedly hit throughout evolution and silenced eventually by mutations in the glycine residues of the collagen-like region. Our results indicate that the MBL1P1 gene has been selectively turned off during evolution through the same molecular mechanisms causing the MBL2 variant alleles in man, suggesting an evolutionary selection for low-producing MBL genes.     

蒙古族人MBL基因exon I 54位密码子点突变频率与其血浆含量的相关性

目的 :初步调查健康蒙古族人甘露 (聚 )糖结合凝集素 (MBL)基因 5 4位密码子点突变的情况 ,检测其血浆MBL的含量 ,探讨两者的相关性。方法 :根据MBL基因序列设计引物 ,建立MBL基因点突变的检测方法 (即PCR RFLP)。用MBLOligomerELISA试剂盒测定血浆MBL的浓度。结果 :建立了特异、敏感的检测MBL基因 5 4位密码子点突变的方法 ,测得健康蒙古族人该基因的突变频率为 0 .18;血浆MBL含量的平均值为(2 .5 3± 1.96 )mg/L ,两者呈负相关 (r=- 0 .6 4 1)。结论 :所建立的测定MBL基因 5 4位密码子点突变的PCR RFLP方法 ,特异性高、重复性好、较灵敏 (最低检出量为 16 0pgDNA) ,并证明该基因的突变频率与其血浆MBL的含量呈负相关。     

Mannose binding lectin: genetics and autoimmune disease

Mannose binding lectin (MBL) is a serum protein with structure and functions similar to those of complement factor C1q, and is a key molecule in innate immunity. Interestingly, absence or extremely low concentration of serum MBL (MBL deficiency) seems to be a risk factor for occurrence of autoimmune diseases, in particular systemic lupus erythematosus. In addition, individuals with MBL deficiency are at risk of infection when in immunocompromised conditions. The concentration of serum MBL is greatly influenced by relatively common single nucleotide polymorphisms of the MBL gene. Therefore, typing of the MBL gene, or measurement of serum MBL may be valuable for determining the risk of infections in patients with systemic autoimmune diseases, who frequently undergo immunosuppressive therapies. MBL deficiency may also be a risk factor for atherosclerosis and arterial thrombosis, both being common complications of autoimmune diseases. On the other hand, MBL may be pathological in tissue injuries, and the precise roles of MBL in autoimmune diseases, and the value of MBL gene typing or serum MBL measurement in a clinical setting are yet to be clarified. Recently, presence of anti-MBL autoantibodies in sera of SLE patients has been reported. The significance of this autoantibody remains to be elucidated.     

Mannose-binding lectin gene polymorphism predicts hospital admissions for COPD infections

Infection frequently causes exacerbations of chronic obstructive pulmonary disease (COPD). Mannose-binding lectin (MBL) is a pattern-recognition receptor that assists in clearing microorganisms. Polymorphisms in the MBL2 gene reduce serum MBL levels and are associated with risk of infection. We studied whether the MBL2 codon 54 B allele affected serum MBL levels, admissions for infective exacerbation in COPD and disease susceptibility. Polymorphism frequency was determined by PCR-RFLP in 200 COPD patients and 104 smokers with normal lung function. Serum MBL was measured as mannan-binding activity in a subgroup of 82 stable COPD patients. Frequency of COPD admissions for infective exacerbation was ascertained for a 2-year period. The MBL2 codon 54 B allele reduced serum MBL in COPD patients. In keeping, patients carrying the low MBL-producing B allele had increased risk of admission for infective exacerbation (OR 4.9, P(corrected)=0.011). No association of MBL2 genotype with susceptibility to COPD was detected. In COPD, serum MBL is regulated by polymorphism at codon 54 in its encoding gene. Low MBL-producing genotypes were associated with more frequent admissions to hospital with respiratory infection, suggesting that the MBL2 gene is disease-modifying in COPD. MBL2 genotype should be explored prospectively as a prognostic marker for infection risk in COPD.     

High-level and effective production of human mannan-binding lectin (MBL) in Chinese hamster ovary (CHO) cells

We have developed a high-expression system of recombinant human mannan-binding lectin (MBL) with CHO cells. Geneticin-resistant transformants harboring human MBL cDNA in the expression vector pNOW/CMV-A were screened by immunoblot analysis for secretion of recombinant MBL. Cloning and selection by both geneticin and methotrexate resulted in the production of recombinant MBL to a final concentration of 128.8 microg/ml in media after four days of culture. SDS-PAGE and gel-filtration analyses showed that recombinant MBL is characterized by two lower-order oligomeric structures (apparent molecular weights: 1150 kDa and 300 kDa) compared to native MBL (apparent molecular weight: 1300 kDa). The recombinant human MBL has both sugar-binding and complement activation activity and, like native MBL, can inhibit hemagglutination of influenza A virus. Lectin blots with recombinant MBL indicate that it can bind such microorganisms as HIV and influenza virus suggesting that it might inhibit their infection of hosts. This high-level expression of human MBL with the full range of biological activity will be useful for studies on the immunological role of MBL in humans.