Complement activation targeted inhibitor C2-FH ameliorates acetaminophen-induced liver injury in mice

BACKGROUND Complement activation is recognized as an important factor in the progression of liver damage caused by acetaminophen(APAP).However,the role of the complement inhibitor C2-FH in APAP-induced liver injury remains unclear.AIM To explore C2-FH in protecting against APAP-induced liver injury by inhibiting complement activation.METHODS A model of APAP-induced liver injury was used to study the protective effect of C2-FH on liver injury.C2-FH was administered through intraperitoneal injection 30 minutes after APAP treatment.We detected the effects of C2-FH on liver function,inflammatory response and complement activation.Additionally,RNA-sequencing(RNA-Seq)analysis was conducted to understand the mechanism through which C2-FH provides protection against APAP-induced liver injury.RESULTS C2-FH inhibited the increase in serum alanine aminotransferase activity,aspartate aminotransferase activity and lactate dehydrogenase,and reduced liver tissue necrosis caused by APAP.Moreover,it attenuated the inflammatory response and inhibited complement activation in APAP-induced liver injury.RNA-Seq analysis provided additional explanations for the protective role of C2-FH against APAP-induced liver injury.CONCLUSION C2-FH attenuates APAP-induced liver injury by inhibiting complement activation.

Complement-dependent neuroinflammation in spinal cord injury:from pathology to therapeutic implications

Spinal cord injury remains a major cause of disability in young adults,and beyond acute decompression and rehabilitation,there are no pharmacological treatments to limit the progression of injury and optimize recovery in this population.Following the thorough investigation of the complement system in triggering and propagating cerebral neuroinflammation,a similar role for complement in spinal neuroinflammation is a focus of ongoing research.In this work,we survey the current literature investigating the role of complement in spinal cord injury including the sources of complement proteins,triggers of complement activation,and role of effector functions in the pathology.We study relevant data demonstrating the different triggers of complement activation after spinal cord injury including direct binding to cellular debris,and or activation via antibody binding to damage-associated molecular patterns.Several effector functions of complement have been implicated in spinal cord injury,and we critically evaluate recent studies on the dual role of complement anaphylatoxins in spinal cord injury while emphasizing the lack of pathophysiological understanding of the role of opsonins in spinal cord injury.Following this pathophysiological review,we systematically review the different translational approaches used in preclinical models of spinal cord injury and discuss the challenges for future translation into human subjects.This review emphasizes the need for future studies to dissect the roles of different complement pathways in the pathology of spinal cord injury,to evaluate the phases of involvement of opsonins and anaphylatoxins,and to study the role of complement in white matter degeneration and regeneration using translational strategies to supplement genetic models.

Antibodies elicited by Newcastle disease virus-vectored H7N9 avian influenza vaccine are functional in activating the complement system

H7N9 subtype avian influenza virus poses a great challenge for poultry industry.Newcastle disease virus(NDV)-vectored H7N9 avian influenza vaccines(NDV_(vec)H7N9)are effective in disease control because they are protective and allow mass administration.Of note,these vaccines elicit undetectable H7N9-specific hemagglutination-inhibition(HI)but high IgG antibodies in chickens.However,the molecular basis and protective mechanism underlying this particular antibody immunity remain unclear.Herein,immunization with an NDV_(vec)H7N9 induced low anti-H7N9 HI and virus neutralization titers but high levels of hemagglutinin(HA)-binding IgG antibodies in chickens.Three residues(S150,G151 and S152)in HA of H7N9 virus were identified as the dominant epitopes recognized by the NDV_(vec)H7N9 immune serum.Passively transferred NDV_(vec)H7N9 immune serum conferred complete protection against H7N9 virus infection in chickens.The NDV_(vec)H7N9 immune serum can mediate a potent lysis of HA-expressing and H7N9 virus-infected cells and significantly suppress H7N9 virus infectivity.These activities of the serum were significantly impaired after heat-inactivation or treatment with complement inhibitor,suggesting the engagement of the complement system.Moreover,mutations in the 150-SGS-152 sites in HA resulted in significant reductions in cell lysis and virus neutralization mediated by the NDV_(vec)H7N9 immune serum,indicating the requirement of antibody-antigen binding for complement activity.Therefore,antibodies induced by the NDV_(vec)H7N9 can activate antibody-dependent complement-mediated lysis of H7N9 virus-infected cells and complement-mediated neutralization of H7N9 virus.Our findings unveiled a novel role of the complement in protection conferred by the NDV_(vec)H7N9,highlighting a potential benefit of engaging the complement system in H7N9 vaccine design.

Repetitive traumatic brain injury–induced complement C1–related inflammation impairs long-term hippocampal neurogenesis

Repetitive traumatic brain injury impacts adult neurogenesis in the hippocampal dentate gyrus,leading to long-term cognitive impairment.However,the mechanism underlying this neurogenesis impairment remains unknown.In this study,we established a male mouse model of repetitive traumatic brain injury and performed long-term evaluation of neurogenesis of the hippocampal dentate gyrus after repetitive traumatic brain injury.Our results showed that repetitive traumatic brain injury inhibited neural stem cell proliferation and development,delayed neuronal maturation,and reduced the complexity of neuronal dendrites and spines.Mice with repetitive traumatic brain injuryalso showed deficits in spatial memory retrieval.Moreover,following repetitive traumatic brain injury,neuroinflammation was enhanced in the neurogenesis microenvironment where C1q levels were increased,C1q binding protein levels were decreased,and canonical Wnt/β-catenin signaling was downregulated.An inhibitor of C1 reversed the long-term impairment of neurogenesis induced by repetitive traumatic brain injury and improved neurological function.These findings suggest that repetitive traumatic brain injury–induced C1-related inflammation impairs long-term neurogenesis in the dentate gyrus and contributes to spatial memory retrieval dysfunction.

Association of complement components with risk of colorectal cancer:A systematic review and meta-analysis

BACKGROUND Complement components could contribute to the tumor microenvironment and the systemic immune response.Nevertheless,their role in colorectal cancer(CRC)remains a contentious subject.AIM To elucidate the relationship between complement components and CRC risk and clinical characteristics.METHODS Searches were conducted in PubMed,the Cochrane Library,and the China National Knowledge Infrastructure database until June 1,2023.We included cohort studies encompassing participants aged≥18 years,investigating the association between complement components and CRC.The studies were of moderate quality or above,as determined by the Agency for Healthcare Research and Quality.The meta-analysis employed fixed-effects or random-effects models based on the I^(2)test,utilizing risk ratio(RR)and their corresponding 95%confidence interval(CI)for outcomes.Sensitivity and subgroup analyses were performed to validate the robustness of the collective estimates and identify the source of heterogeneity.RESULTS Data from 15 studies,comprising 1631 participants that met the inclusion criteria,were included in the meta-analysis.Our findings indicated that protein levels of cluster of differentiation 46(CD46)(RR=3.66,95%CI:1.75-7.64,P<0.001),CD59(RR=2.86,95%CI:1.36-6.01,P=0.005),and component 1(C1)(RR=5.88,95%CI:1.75-19.73,P=0.004)and serum levels of C3(standardized mean difference=1.82,95%CI:0.06-3.58,P=0.040)were significantly elevated in patients with CRC compared to healthy controls.Strong expression of CD55 or CD59 was associated with a higher incidence of lymph node metastasis,whereas strong CD46 expression correlated with a higher incidence of tumor differentiation compared to low CD46 expression(P<0.05 for all).Although specific pooled results demonstrated notable heterogeneity,subgroup analyses pointed to regional differences as the primary source of inconsistency among the studies.CONCLUSION Our analysis underscores that increased levels of specific complement components are associated with a heightened risk of CRC,emphasizing the potential significance of monitoring elevated complement component levels.

Tumor-related factor complement Clq/TNF-related protein 6 affects the development of digestive system tumors through the phosphatidylinositol 3-kinase pathway

In this editorial,we review the work of Razali et al published in World J Gas-troenterology,with a particular focus on the effect of rs10889677 variation in the phosphatidylinositol 3-kinase(PI3K)pathway and buparlisib on colitis-associated cancer.The role of PI3K in promoting cancer progression has been widely recognized,as it is involved in regulating the survival,differentiation,and prolif-eration of cancer cells.The complement Clq/TNF-related protein 6(CTRP6)is a newer tumor-associated factor.Recent studies have revealed the pro-tumor effect of CTRP6 in gastric cancer,hepatocellular carcinoma,colorectal cancer,and other gastrointestinal tumors through the PI3K pathway.This article attempts to reveal the mechanism through which the CTRP6 affects the development of digestive system tumors through the PI3K pathway by summarizing recent research.

Complement factor Ⅰ knockdown inhibits colon cancer development by affecting Wnt/β-catenin/c-Myc signaling pathway and glycolysis

BACKGROUND Colon cancer(CC)occurrence and progression are considerably influenced by the tumor microenvironment.However,the exact underlying regulatory mechanisms remain unclear.AIM To investigate immune infiltration-related differentially expressed genes(DEGs)in CC and specifically explored the role and potential molecular mechanisms of complement factor I(CFI).METHODS Immune infiltration-associated DEGs were screened for CC using bioinformatics.Quantitative reverse transcription polymerase chain reaction was used to examine hub DEGs expression in the CC cell lines.Stable CFI-knockdown HT29 and HCT116 cell lines were constructed,and the diverse roles of CFI in vitro were assessed using CCK-8,5-ethynyl-2’-deoxyuridine,wound healing,and transwell assays.Hematoxylin and eosin staining and immunohistochemistry staining were employed to evaluate the influence of CFI on the tumorigenesis of CC xenograft models constructed using BALB/c male nude mice.Key proteins associated with glycolysis and the Wnt pathway were measured using western blotting.RESULTS Six key immune infiltration-related DEGs were screened,among which the expression of CFI,complement factor B,lymphoid enhancer binding factor 1,and SRY-related high-mobility-group box 4 was upregulated,whereas that of fatty acid-binding protein 1,and bone morphogenic protein-2 was downregulated.Furthermore,CFI could be used as a diagnostic biomarker for CC.Functionally,CFI silencing inhibited CC cell proliferation,migration,invasion,and tumor growth.Mechanistically,CFI knockdown downregulated the expression of key glycolysis-related proteins(glucose transporter type 1,hexokinase 2,lactate dehydrogenase A,and pyruvate kinase M2)and the Wnt pathway-related proteins(β-catenin and c-Myc).Further investigation indicated that CFI knockdown inhibited glycolysis in CC by blocking the Wnt/β-catenin/c-Myc pathway.CONCLUSION The findings of the present study demonstrate that CFI plays a crucial role in CC development by influencing glycolysis and the Wnt/β-catenin/c-Myc pathway,indicating that it could serve as a promising target for therapeutic intervention in CC.

Complement involvement in kidney diseases:From physiopathology to therapeutical targeting

Complement cascade is involved in several renal diseases and in renal transplantation. The different components of the complement cascade might represent an optimal target for innovative therapies. In the frst section of the paper the authors review the physiopathology of complement involvement in renal diseases and transplantation. In some cases this led to a reclassifcation of renal diseases moving from a histopathological to a physiopathologicalclassification. The principal issues afforded are： renal diseases with complement over activation, renal diseases with complement dysregulation, progression of renal diseases and renal transplantation. In the second section the authors discuss the several complement components that could represent a therapeutic target. Even if only the anti C5 monoclonal antibody is on the market, many targets as C1, C3, C5a and C5aR are the object of national or international trials. In addition, many molecules proved to be effective in vitro or in preclinical trials and are waiting to move to human trials in the future.

Different serum levels of IgG and complements and recurrence rates in IgG4-positive and negative lacrimal gland benign lymphoepithelial lesion

·AIM:To analyze the differences in immune indicators and prognosis between Ig G4-positive and negative lacrimal gland benign lymphoepithelial lesion(LGBLEL).·METHODS:This was a single-center retrospective clinical study including 105 cases of Ig G4-positive LGBLEL and 41 cases of Ig G4-negative LGBLEL.Basic information,related indicators of peripheral venous blood samples using immunoscattering turbidimetry,treatment(partial surgical excision and glucocorticoid therapy)and prognosis(recurrence and death)were collected.Survival curves for recurrence were created using the Kaplan-Meier analysis.Univariate analysis and multivariate regression analysis were used to analyze prognostic factors.·RESULTS:The mean age was 50.10±14.23y and 44.76±11.43y(P=0.033)in Ig G4-positive and negative group respectively.The serum C3 and C4 was lower in Ig G4-positive group(P=0.005,P=0.002),while the serum Ig G and Ig G2 was higher in Ig G4-positive group(P=0.000 and P=0.008).Twenty-one cases had recurrence in Ig G4-positive group and 3 cases recurrence in Ig G4-negative group.The 5-year recurrence-free cumulative percentages of Ig G4-positive group was 81.85%,and 83.46%in the Ig G-negative group(P=0.216).The history of preoperative glucocorticoid therapy,serum C4,Ig G1 and Ig G2 were the factors affecting recurrence in Ig G4-positive group,while serum C4,and Ig G1 were the factors affecting recurrence of LGBLEL.·CONCLUSION:Serum C4 and Ig G1 are the factors affecting recurrence of LGBLEL,while the Ig G4 does not affect recurrence of LGBLEL.

Association of C-reactive protein and complement factor H gene polymorphisms with risk of lupus nephritis in Chinese population

BACKGROUND Complement overactivation is a major driver of lupus nephritis(LN).Impaired interactions of C-reactive protein(CRP)with complement factor H(CFH)have been shown as a pathogenic mechanism that contributes to the overactivation of complement in LN.However,genetic variations of neither CRP nor CFH show consistent influences on the risk of LN.AIM To examine whether genetic variations of CRP and CFH in combination can improve the risk stratification in Chinese population.METHODS We genotyped six CRP single nucleotide polymorphisms(SNPs)(rs1205,rs3093062,rs2794521,rs1800947,rs3093077,and rs1130864)and three CFH SNPs(rs482934,rs1061170,and rs1061147)in 270 LN patients and 303 healthy subjects.RESULTS No linkage was found among CRP and CFH SNPs,indicating lack of genetic interactions between the two genes.Moreover,CRP and CFH SNPs,neither individually nor in combination,are associated with the risk or clinical manifestations of LN.Given the unambiguous pathogenic roles of the two genes.CONCLUSION These findings suggest that the biological effects of most genetic variations of CRP and CFH on their expressions or activities are not sufficient to influence the disease course of LN.

Complement Protection Against Immune Complex and Acute Glomerulonephritis

in this study serum complement mediated immune complex solubilizing capacity (CMSC) and immune complement precipitation capacity (ICPIC) of 32 children with acute glomerulonephritis (AGN) were measured. The data showed that the level of serum CMSC and ICPIC was markedly decreased in acute phase and returned to normal in the 7th week after onset of disease.Correlation analysis revealed that there were positive correlation between the level of serum CMSC and ICPIC and the serum concentration of CH50, C3, C4, but no linear correlation between the level of serum CMSC and ICPIC and the amount of CIC. These results suggest that the declined serum CMSC and ICPIC in AGN may be associ ated with the pathogenesis of AGN.

英藏“补语”比较及Complement一词藏译略考

在汉语基础薄弱的偏远藏族农牧区的英文教学中,进行英藏语法直接的比较,对该地区英语教学效果的提高具有积极意义。本文以英文语法教学为主体,旨在通过对英藏基础句法中"Complement"一词的直接对比和语法术语的藏译探讨,望能帮助解决农牧区藏族学生英文教学中对该语法盲点的理解困扰。

C3 Glomerulopathy and Therapeutic Potential of C5 Complement Inhibitors

C3 glomerulopathy is a disease including both dense deposit disease and C3 glomerulonephritis has an estimated prevalence of 2 to 3 per million. Originally, these pathologies were defined as glomerular pathology characterized by accumulation of C3 with absent or scanty immunoglobulin deposition. The keystone defect in both of these pathologies is the unregulated hyperactivity of alternative complement pathway. Specifically, in C3 glomerulopathy patients, there exists a prolongation of C3 cleavage which causes the uncontrolled alternative pathway activation. Many treatments have been investigated for treating C3 glomerulopathy to little or no avail, including calcineurin inhibitors, plasmapharesis, and anti-CD20 monoclonal antibodies. The next logical step is exploring the efficacy of anti-C5 monoclonal antibody therapy in C3 glomerulopathies to target the specific pathophysiology of this particular disease. Eculizumab is an anti-C5 monoclonal antibody that blocks the terminal step of complement activation. This drug has proven to be an effective treatment in other nephrologic pathologies that are caused by complement dysregulation. Here in this paper we discuss and present various case studies and clinical trials available that experiment with Eculizumab in patients with either dense deposit disease or C3 glomerulonephritis. In most of these patients, treatment with Eculizumab has demonstrated clinical and biochemical improvements in kidney function. These results provide encouraging evidence that suggest Eculizumab as a promising therapy for patients with C3 glomerulopathy and warrant that more extensive clinical trials can be designed as a next step.

中外学习者使役结构使用对比研究——以“make+object+complement”结构为例

中国大学英语学习者在表达使役关系的时候多倾向于使用"make+object+complement"结构,但对中国学生在使用这一结构和本族语者使用这一结构存在哪些差异及其原因的研究却不多。利用WordNeighbors数据库对本族语者使用这一结构的情况进行了调查研究,结果显示:就使用频率而言,本族语者也比较频繁地使用这一结构,但在具体用法上与汉语存在两点不同之处。究其原因,主要是受母语负迁移的影响。研究表明,输入的匮乏是造成中国学习者过度依赖母语的一个原因。

Complement and its role in innate and adaptive immune responses

The complement system plays a crucial role in the innate defense against common pathogens. Activation of complement leads to robust and efficient proteolytic cascades, which terminate in opsonization and lysis of the pathogen as well as in the generation of the classical inflammatory response through the production of potent proinflammatory molecules. More recently, however, the role of complement in the immune response has been expanded due to observations that link complement activation to adaptive immune responses. It is now appreciated that complement is a functional bridge between innate and adaptive immune responses that allows an integrated host defense to pathogenic challenges. As such, a study of its functions allows insight into the molecular underpinnings of host-pathogen interactions as well as the organization and orchestration of the host immune response. This review attempts to summarize the roles that complement plays in both innate and adaptive immune responses and the consequences of these interactions on host defense.

Analysis of immunoglobulin, complements and CRP levels in serum of captive northern pig-tailed macaques （Macaca leonina）

The northem pig-tailed macaque （NPM, Macaca leonina） has become a widely used animal model in biomedical research. In this study, we measured serum immunoglobulin IgG, IgM, IgA, complement C3, C4 and CRP levels in 3-11 year old captive northem pig-tailed macaques using HITACHI 7600-20 automated chemistry analyzer in order to determine the influences of age and gender on these items. The results showed that serum IgA, IgM, C3 and C4 levels were not correlated with age （P〉0.05）, while serum IgG levels increased progressively with age （r=0.202; P=0.045）. Serum IgG, IgA, IgM and C3 levels were higher in females than in males （P〈0.05）. Moreover, serum C3 concentration was both positively and strongly correlated with that of C4 （r=0.700; P〈0.0001）. This study provides basic serum immunoglobulin and complement data of captive northem pig-tailed macaques, which may prove useful for future breeding efforts and biomedical research.

Effect of IL-4 on altered expression of complement activation regulators in rat pancreatic cells during severe acute pancreatitis

AIM： To investigate the effect of IL-4 on the altered expression of complement activation regulators in pancreas and pancreatic necrosis during experimental severe acute pancreatitis （SAP）. METHODS： SAP model of rats was established by retrograde injection of 5% sodium taurocholate （1 mL/kg） into the pancreatic duct. We immunohistochemically assayed the expression of three complement activation regulators： decay accelerating factor （DAF; CD55）, 20 ku homologous restriction factor （HRF20; CD59） and membrane cofactor protein （MCP; CEH6）, in the pancreatic acinar cells of rats at 0, 3, 6, 12, and 24 h after the induction of SAP model. Meanwhile the levels of amylase and lipase were determined, and morphological examination was performed. Then, 61 rats were randomly divided into three groups. Group A （n = 21） received no treatment after the SAP model was established; group B （n = 20） was given IL-4 （8 IJg/animal） intraperitoneally 0.5 h before the SAP model was established; group C （n = 20） was given IL-4 （8 μg/animal） intraperitoneaUy 0.5 h after the SAP model was established. Plasma amylase and lipase, extent of pancreatic necrosis and expression of complement activation regulators were investigated 6 h after the induction of SAP model. RESULTS： Three complement activation regulators were all expressed in pancreatic acinar cells. MCP was not found on the basolateral surface as reported. Contrary to the gradually increasing plasma level of amylase and lipase, expression of complement activation regulators decreased after SAP model was set up. At the same time, the severity of pancreatic necrosis was enhanced. A strong negative correlation was found between the expression of MCP, DAF, CD59 in pancreatic acinar cells and the severity of pancreatic necrosis （r = -0.748, -0.827, -0.723; P〈0.01）. In the second series of experiments, no matter when the treatment of IL-4 was given （before or after the induction of SAP model）, the serum level of amylase or lipase was decreased and the extent of pancreatic necrosis was ameliorated significantly. Compared to SAP control group, the expression of DAF and CD59 in pancreas was reinforced when IL-4 was given before the induction of SAP model （P〈0.01, P〈0.05）, but the expression of MCP was not influenced （P〉0.05）. The expression of DAF was enhanced, when IL-4 was given after the induction of SAP model （P〈0.05）, but the expression of CD59 and MCP did not change （P〉0.05）. CONCLUSION： Complement activation regulators may participate in the pathogenesis of pancreatic inflammation. Downregulation of complement activation regulators expression may be one of the causes of pancreatic necrosis. IL-4 treatment may control SAP aggravation by enhancing expression of DAF and CD59 in pancreas and decreasing pancreatic necrosis. Moreover, DAF and CD59 may play an important role in the regulation of complement activation regulators during SAP.

Complements are involved in alcoholic fatty liver disease, hepatitis and fibrosis

The complement system is a key component of the body's immune system. When abnormally activated, this system can induce inflammation and damage to normal tissues and participate in the development and progression of a variety of diseases. In the past, many scholars believed that alcoholic liver disease(ALD) is induced by the stress of ethanol on liver cells, including oxidative stress and dysfunction of mitochondria and protease bodies, causing hepatocyte injury and apoptosis. Recent studies have shown that complement activation is also involved in the genesis and development of ALD. This review focuses on the roles of complement activation in ALD and of therapeutic intervention in complement-activation pathways. We intend to provide new ideas on the diagnosis and treatment of ALD.

Cell cycle and complement inhibitors may be specific for treatment of spinal cord injury in aged and young mice: transcriptomic analyses

Previous studies have reported age-specific pathological and functional outcomes in young and aged patients suffering spinal cord injury,but the mechanisms remain poorly understood. In this study, we examined mice with spinal cord injury. Gene expression profiles from the Gene Expression Omnibus database （accession number GSE93561） were used, including spinal cord samples from 3 young injured mice （2–3-months old, induced by Impactor at Th9 level） and 3 control mice （2–3-months old, no treatment）, as well as 2 aged injured mice （15–18-months old, induced by Impactor at Th9 level） and 2 control mice （15–18-months old, no treatment）. Differentially expressed genes （DEGs） in spinal cord tissue from injured and control mice were identified using the Linear Models for Microarray data method,with a threshold of adjusted P 〈 0.05 and ｜logFC（fold change）｜ 〉 1.5. Protein–protein interaction networks were constructed using data from the STRING database, followed by module analysis by Cytoscape software to screen crucial genes. Kyoto encyclopedia of genes and genomes pathway and Gene Ontology enrichment analyses were performed to investigate the underlying functions of DEGs using Database for Annotation, Visualization and Integrated Discovery. Consequently, 1,604 and 1,153 DEGs were identified between injured and normal control mice in spinal cord tissue of aged and young mice, respectively. Furthermore, a Venn diagram showed that 960 DEGs were shared among aged and young mice, while 644 and 193 DEGs were specific to aged and young mice, respectively. Functional enrichment indicates that shared DEGs are involved in osteoclast differentiation, extracellular matrix–receptor interaction, nuclear factor-kappa B signaling pathway, and focal adhesion. Unique genes for aged and young injured groups were involved in the cell cycle （upregulation of PLK1） and complement （upregulation of C3） activation, respectively. These findings were confirmed by functional analysis of genes in modules （common, 4; aged, 2; young, 1） screened from protein–protein interaction networks. Accordingly, cell cycle and complement inhibitors may be specific treatments for spinal cord injury in aged and young mice, respectively.

Characterization and Expression Analysis of a Complement Component Gene in Sea Cucumber(Apostichopus japonicus)

The complement system plays a crucial role in the innate immune system of animals. It can be activated by distinct yet overlapping classical, alternative and lectin pathways. In the alternative pathway, complement factor B(Bf) serves as the catalytic subunit of complement component 3(C3) convertase, which plays the central role among three activation pathways. In this study, the Bf gene in sea cucumber(Apostichopus japonicus), termed Aj Bf, was obtained by rapid amplification of c DNA ends(RACE). The full-length c DNA of Aj Bf was 3231 bp in length barring the poly(A) tail. It contained an open reading frame(ORF) of 2742 bp encoding 913 amino acids, a 105 bp 5'-UTR(5'-terminal untranslated region) and a 384 bp 3'-UTR. Aj Bf was a mosaic protein with six CCP(complement control protein) domains, a VWA(von Willebrand factor A) domain, and a serine protease domain. The deduced molecular weight of Aj Bf protein was 101 k Da. Quantitative real time PCR(q RT-PCR) analysis indicated that the expression level of Aj Bf in A. japonicus was obviously higher at larval stage than that at embryonic stage. Expression detection in different tissues showed that Aj Bf expressed higher in coelomocytes than in other four tissues. In addation, Aj Bf expression in different tissues was induced significantly after LPS or Poly I:C challenge. These results indicated that Aj Bf plays an important role in immune responses to pathogen infection.