Mannose-binding lectin without the aid of its associated serine proteases alters lipopolysaccharide-mediated cytokine/chemokine secretion from human endothelial cells

Coupling between certain pathogen-associated molecular patterns and corresponding pattern recognition receptors of endothelial cells is important for the mediation of vascular inflammatory responses. Mannose-binding lectin (MBL) recognizes certain carbohydrate structures of microbes and subsequently activates the complement system as well as facilitates the phagocytosis of targets. We investigated whether MBL can intervene in the interaction between bacterial lipopolysaccharide (LPS) and endothelial cells to modulate subsequent inflammatory responses. In response to LPS, human umbilical vein endothelial cells (HUVEC) produced various cytokines/chemokines. Addition of the purified human MBL/MBL-associated serine proteases (MASP) complex or recombinant human MBL enhanced LPS-mediated cytokine/chemokine secretion by HUVEC, including interleukin-8 (IL-8), IL-6 and monocyte chemoattractant protein-1 in a dose-dependent manner. This enhancing effect was ameliorated by the addition of anti-MBL antibody or mannan. Among the cytokines/chemokines we analysed, IL-6 showed the greatest increase of secretion in the presence of native MBL/MASP complex or recombinant MBL. MBL, regardless of its association with MASP, alters LPS-mediated cytokine/chemokine secretion of HUVEC. Besides the well-known functions of MBL, to activate the lectin-complement pathway and to facilitate clearance of targets, alteration of cytokine/chemokine secretion may provide an additional role for MBL in modulating vascular inflammation.     

人MASP1和MASP2 C端片段的原核表达

目的在大肠杆菌中表达人甘露聚糖结合凝集素(MBL)相关丝氨酸蛋白酶1、2(MASP1、MASP2)C端片段。方法采用PCR技术从分别含人MASP1、MASP2cDNA的质粒pGEM-MASP1、pGEM-MASP2中扩增MASP1、MASP2C端基因片段,将其插入原核表达载体pET17b,转化感受态大肠杆菌BL21(DE3),诱导表达MASP1、MASP2C端蛋白,通过Ni2+-NTA亲和层析柱纯化目的蛋白,以SDS-PAGE、Western blot和ELISA进行鉴定。结果分别从pGEM-MASP1和pGEM-MASP2中扩增到约1300bp的基因片段,构建成重组表达载体,经酶切出现约3300bp和1300bp片段,测序结果与预期的完全一致。纯化蛋白经SDS-PAGE可见Mr40000蛋白带,该蛋白可与抗His抗体反应。结论获得了重组人MASP1和MASP2C端片段蛋白及其表达菌株,为MASP分子的进一步研究提供了条件。     

人MASP1 N端片段原核表达载体的构建及其表达

目的:在大肠杆菌中表达人甘露聚糖结合凝集素(MBL)相关丝氨酸蛋白酶1(MASP1)N端片段.方法:采用PCR技术从含人MASP1 cDNA的质粒pGEM-MASP1中扩增MASP1-N端基因片段,将其插入原核表达载体pGEX4T-1,转化BL21(DE3)感受态菌诱导表达MASP1-N端蛋白,通过GSTrap亲合层析柱纯化目的蛋白,以SDS-PAGE和Westernblot进行鉴定,并以ELISA分析了目的蛋白与重组MBL-CLR、重组MBL的结合活性.结果:从pGEM-MASP1中扩增得到约860 bp的基因片段,构建成重组载体经酶切出现约4 900 bp和860 bp片段,测序结果与预期的完全一致.纯化蛋白经SDS-PAGE可见Mr60000蛋白带,该蛋白可与抗GST抗体反应并能与重组人MBL-CLR、重组人MBL蛋白结合.结论:获得了表达人MASP1 N端片段的大肠杆菌菌株和重组人MASP1 N端片段/GST融合蛋白,为MASP1分子的进一步研究提供了条件.     

人甘露聚糖结合凝集素相关丝氨酸蛋白酶2 N端片段的原核表达

目的 在大肠杆菌中表达人甘露聚糖结合凝集素(MBL)相关丝氨酸蛋白酶2(MASP2)N端片段.方法 应用PCR技术从含人MASP2 cDNA的质粒pGEM-MASP2中扩增MASP2-N端基因片段,将其克隆至pGEX4T-1原核表达载体,转化BL21(DE3)感受态菌诱导表达MASP2-N端蛋白,通过GSTrap亲合层析柱纯化目的蛋白,以SDS-PAGE和Western blot进行鉴定,并以ELISA分析了目的蛋白与MBL-CLR结合的活性.结果 从pGEM-MASP2中扩增得到约840 bp的基因片段,构建成重组载体经酶切出现约4 900 bp和840 bp片段,测序结果与预期的完全一致.纯化蛋白经SDS-PAGE可见Mr 60 000蛋白带,该蛋白可与抗GST抗体反应并能与重组人MBL-CLR蛋白结合.结论 获得了表达人MASP2 N端片段的大肠杆菌菌株和重组人MASP2N端片段/GST融合蛋白,为MASP2分子的进一步研究提供了条件.     

Mannose-binding lectin engagement with late apoptotic and necrotic cells

The serum opsonin mannose-binding lectin (MBL) has been shown to be involved in the handling of apoptotic cells. However, at what stage in the process this happens and whether this mediates activation of complement is unknown. Cells rendered apoptotic or necrotic were incubated with purified MBL/MBL-associated serine protease (MASP) complexes and assessed by flow cytometry and fluorescence microscopy. MBL bound specifically to late apoptotic cells, as well as to apoptotic blebs and to necrotic cells, but not to early apoptotic cells. Binding of MBL could be inhibited by EDTA as well as with an antibody against the CRD region. Addition of C1q, another serum opsonin involved in the handling of apoptotic cells, prior to MBL partly inhibited MBL binding to apoptotic cells and vice versa. MBL/MASP could initiate deposition of purified complement C4 on the target cells. However, addition of MBL/MASP to whole serum deficient for both C1q and MBL did not enhance deposition of C4, but MBL enhanced phagocytosis of apoptotic cells by macrophages. These results demonstrate that MBL interacts with structures exposed on cells rendered late apoptotic or necrotic and facilitates uptake by macrophages. Thus, MBL may promote non-inflammatory sequestration of dying host cells.     

Effect of probenecid on phagocytosis and intracellular killing of Staphylococcus aureus and Escherichia coli by human monocytes and granulocytes.

The present study concerns the effects of probenecid on the phagocytosis and intracellular killing of Staphylococcus aureus and Escherichia coli by human monocytes and granulocytes. In both monocytes and granulocytes the inhibitory effect on phagocytosis was very small. Inhibition of intracellular killing of S. aureus by monocytes and granulocytes by probenecid was concentration dependent, being half-maximal at about 2 mM probenecid, and near-maximal at about 5 mM probenecid. The intracellular killing could also be inhibited when probenecid was added when this process was already started. Probenecid also inhibited the intracellular killing of E. coli by granulocytes, but not by monocytes. In the concentration range used, probenecid had no toxic effect on phagocytes or bacteria during the 2 hr of the experiments.     

Polyamino acid enhancement of bacterial phagocytosis by human polymorphonuclear leukocytes and peritoneal macrophages.

Cationic polyamino acids are known to enhance a variety of cell-cell interactions by virtue of their ability to alter electrostatic forces of cell surfaces. In this study, the effect of polyamino acids on phagocytosis of 3H-labeled bacteria by human polymorphonuclear leukocytes (PMNs) and peritoneal macrophages was investigated. Negatively charged and neutral polyamino acids did not influence phagocytosis of unopsonized Staphylococcus epidermidis, whereas protamine, poly-L-arginine, and poly-L-lysine stimulated phagocytosis in a dose-dependent manner. At 50 micrograms/ml, greater than 30% uptake by PMNs was seen with each of these cationic polyamino acids. Although cationic polyamino acids promoted PMN and peritoneal macrophage phagocytosis of unopsonized S. epidermidis, Staphylococcus aureus M (encapsulated) and M variant (unencapsulated), and Escherichia coli J5, little effect was seen with the parent E. coli O111:B4 or a serotype O222:H16 strain. Pretreatment of bacteria and phagocytes separately demonstrated that the phagocytosis-promoting property of polyamino acids is manifest predominantly on the bacteria. Bacteria pretreated with cationic polyamino acids also elicited a PMN chemiluminescent response, and PMN-associated bacteria were killed, as determined by a fluorochrome microassay. Thus, cationic polyamino acids promote the phagocytosis and killing of many but not all bacterial strains, and in this respect polyamino acids function as opsonins.     

Deficient intracellular killing of bacteria by murine alveolar macrophages

Microbiologic methods were used to assess the in vitro phagocytosis and intracellular killing of various species of bacteria by freshly isolated murine peritoneal and alveolar macrophages. Peritoneal macrophages showed effective phagocytosis of opsonized Streptococcus pneumoniae, Streptococcus pyogenes, Pseudomonas aeruginosa, Staphylococcus epidermidis, and Listeria monocytogenes, and moderate ingestion of Staphylococcus aureus and Escherichia coli. Alveolar macrophages were poor in phagocytosing opsonized S. pyogenes, S. aureus, and E. coli; ingestion of S. pneumoniae, P. aeruginosa, and S. epidermidis was moderate. Peritoneal macrophages killed 40 to 80% of these bacteria intracellularly, but alveolar macrophages showed almost no intracellular killing of bacteria. To find out whether there is a correlation between the poor bactericidal activity of alveolar macrophages and the oxygen-dependent microbicidal mechanisms of these cells, we determined the uptake of oxygen and the release of superoxide anion and hydrogen peroxide by macrophages at rest and after stimulation with phorbol myristate acetate (PMA) or opsonized S. aureus. Upon exposure to these stimuli, peritoneal macrophages, but not alveolar macrophages, showed an increased uptake of oxygen and release of superoxide anion and hydrogen peroxide. Because alveolar macrophages contain surface active material (SAM), we investigated the phagocytosis and intracellular killing of bacteria and the release of hydrogen peroxide by peritoneal macrophages pretreated with SAM. The results showed reduced phagocytosis and impaired intracellular killing of S. epidermidis by these macrophages. The release of hydrogen peroxide by SAM-pretreated peritoneal macrophages upon stimulation with PMA or opsonized S. aureus was equal to that of the control peritoneal macrophages.(ABSTRACT TRUNCATED AT 250 WORDS)     

Differences in phagocytosis and killing by alveolar macrophages from humans, rabbits, rats, and hamsters.

Phagocytosis and killing by alveolar macrophages from humans, rabbits, rats, and hamsters, were compared in vitro. In the absence of serum opsonins, human alveolar macrophages could phagocytize Staphylococcus aureus Cowan I (protein A positive), but not S. aureus EMS (protein A negative) or Pseudomonas aeruginosa MN. In contrast, rabbit, rat, and hamster alveolar macrophages did not phagocytize S. aureus Cowan I or other nonopsonized bacteria. Human alveolar macrophages, but not other species, stained positively with fluorescein isothiocyanate-conjugated protein A. When opsonized bacterial were studied, phagocytosis by human, rabbit, and hamster alveolar macrophages was found to be mediated by both Fc and C3 receptors. However, only Fc receptor-mediated phagocytosis of bacteria was demonstrated for rat alveolar macrophages. Differences were also found in the kinetics of bacterial killing by alveolar macrophages from different species. Human and rabbit alveolar macrophages rapidly killed opsonized S. aureus Cowan I. However, bacterial killing by hamster alveolar macrophages proceeded at a slower rate, and rat alveolar macrophages completely failed to kill S. aureus. These significant differences in the function of alveolar macrophages from four different species emphasize the need to document the appropriateness of animal models before using them to predict the biological activities of human alveolar macrophages.     

Mannose-binding lectin enhances the attachment and phagocytosis of mycobacteria in vitro

INTRODUCTION: Phagocytosis is the critical first step in the Mycobacterium (M.) tuberculosis-phagocyte interaction. The process involves microbial ligands and phagocyte surface receptors. It is known that serum mannose-binding lectin (MBL), an innate immune system component, may enhance the uptake of microbes by phagocytic cells and activate the complement system. Since phagocytes are the replicative environment for mycobacteria and, as we described earlier, tuberculosis patients differ from controls in serum MBL level, we asked whether MBL plays a role in promoting M. tuberculosis access to phagocytic cells. MATERIAL/METHODS: To estimate the influence of MBL on the phagocytic process, FITC-labeled Mycobacterium bovis BCG was used as a model bacterium. Neutrophils from healthy individuals were used as phagocytes. Phagocytosis was performed in the presence or absence of recombinant MBL (rMBL; 2 or 20 microg/ml). The activation of complement was determined by dot-blot immune assay with monoclonal antibodies against C5b-C9. RESULTS: We showed that phagocytosis of the bacteria was more intensive in the presence of human rMBL. Both attachment and ingestion of mycobacteria were enhanced when MBL and active complement components (fresh serum) were present in the medium. The dot-blot method showed that the bacteria slightly activated complement by themselves. This effect was enhanced in the phagocyte-bacteria co-cultures containing rMBL. CONCLUSIONS: It is possible that MBL may serve in vivo as one of the factors facilitating the entry of mycobacteria into phagocytes, pathogen spread, and the establishment of infection.     

Bacterial phagocytosis by macrophages from lipopolysaccharide responder and nonresponder mouse strains.

The phagocytic capacity of macrophages from C3H/H3J mice was assessed against lipopolysaccharide-producing (Escherichia coli) and -nonproducing (Staphylococcus aureus) bacteria. Despite their gene-coded unresponsiveness to lipopolysaccharide endotoxin and lymphokines and their defective tumoricidal activity, proteose peptone-induced C3H/HeJ macrophages did not display a defective phagocytic capacity, but rather displayed an enhanced phagocytosis of both bacterial strains compared with macrophages from closely related C3H/HeN mice. Unstimulated peritoneal resident C3H/HeJ macrophages, on the other hand, displayed a normal phagocytic activity toward E. coli and enhanced phagocytosis toward S. aureus.     

Group B streptococcus-induced nitric oxide production in murine macrophages is CR3 (CD11b/CD18) dependent.

Nitric oxide (NO) is produced by murine macrophages in response to cytokines and/or gram-negative bacterial lipopolysaccharide. NO induction by gram-positive bacteria such as group B streptococci (GBS), the major etiologic agents of neonatal pneumonia and meningitis, has received little study. GBS as well as two other gram-positive bacterial species, Staphylococcus aureus and Staphylococcus epidermidis, were found to stimulate NO production in thioglycolate-elicited murine macrophages and in the mouse macrophage cell line J774A.1 in the presence of gamma interferon. Serotype Ia and III GBS were both stimulatory, as were asialo- and type antigen-deficient mutant strains of type III GBS. NO production was dose dependent, inhibitable by L-arginine analogs, and unaffected by polymyxin B. Since phagocytosis by murine and human phagocytes of GBS is dependent on complement receptor type 3 (CR3), the role of CR3 in the NO response to GBS was tested in the CR3-deficient myelomonocytic cell line WEHI-3. GBS did not induce NO, whereas S. aureus or lipopolysaccharide did induce NO in WEHI-3 cells. S. epidermidis, whose nonopsonic phagocytosis is also CR3 dependent, failed to induce NO in WEHI-3 cells. Monoclonal anti-CR3 (anti-CD11b or anti-CD18) in the presence of interferon also induced NO production in thioglycolate-elicited macrophages and in J774A.1 cells but not in WEHI-3 cells. This evidence suggests that ligated CR3 and gamma interferon act synergistically to induce NO production and that CR3 mediates the GBS-induced signal for NO production in interferon-treated macrophages.     

Annexins I and IV inhibit Staphylococcus aureus attachment to human macrophages

Annexins are a family of proteins that bind to phospholipids and carbohydrates in a calcium-dependent manner. They are present in a variety of body fluids. Previous studies have shown that annexins have anti-inflammatory activities for lipid A of Gram-negative bacteria. The present study investigated the effect of annexins on interaction between Gram-positive bacteria and immune cells such as macrophages. Annexins I and IV bound to lipoteichoic acids which are surface molecules on Gram-positive bacteria. Binding of annexins I and IV to whole Staphylococcus aureus (S. aureus) were observed and these bindings were inhibited by lipoteichoic acid from S. aureus. Moreover, annexins I and IV suppressed the attachment of S. aureus to phorbol 12-myristate 13-acetate-treated THP-1 cells (human macrophages). These results suggest that annexins I and IV have ligand specificities toward foreign substances, and that the annexins might have some anti-inflammatory property for Gram-positive bacteria.     

Activation of human THP-1 cells and rat bone marrow-derived macrophages by Helicobacter pylori lipopolysaccharide.

The mechanism by which Helicobacter pylori, which has little or no invasive activity, induces gastric-tissue inflammation and injury has not been well characterized. We have previously demonstrated that water-extracted proteins of H. pylori are capable of activating human monocytes by a lipopolysaccharide (LPS)-independent mechanism. We have now compared activation of macrophages by purified LPS from H. pylori and from Escherichia coli. LPS was prepared by phenol-water extraction from H. pylori 88-23 and from E. coli O55. THP-1, a human promyelomonocytic cell line, and macrophages derived from rat bone marrow each were incubated with the LPS preparations, and cell culture supernatants were assayed for production of tumor necrosis factor alpha (TNF-alpha), prostaglandin E2 (PGE2), and nitric oxide. THP-1 cells showed maximal activation by the LPS molecules after cell differentiation was induced by phorbol 12-myristate 13-acetate. Maximal TNF-alpha and PGE2 production occurred by 6 and 18 h, respectively, in both types of cells. In contrast, NO was produced by rat bone marrow-derived macrophages only and was maximal at 18 h. The minimum concentration of purified LPS required to induce TNF-alpha, PGE2, and NO responses in both types of cells was 2,000- to 30,000-fold higher for H. pylori than for E. coli. Purified LPS from three other H. pylori strains with different polysaccharide side chain lengths showed a similarly low level of activity, and polymyxin B treatment markedly reduced activity as well, suggesting that activation was a lipid A phenomenon. These results indicate the low biological activity of H. pylori LPS in mediating macrophage activation.     

Effect of bacterial competition on the opsonization, phagocytosis, and intracellular killing of microorganisms by granulocytes.

The ingestion of Escherichia coli by human granulocytes in vitro was reduced in the presence of Bacteroides fragilis or Staphylococcus aureus. This reduction of ingestion proved to be mainly attributable to the absence of opsonization of E. coli, which was due to complement consumption by B. fragilis and S. aureus. The intracellular killing of E. coli was decreased in the presence of B. fragilis and S. aureus because of consumption of complement components required for extracellular stimulation of granulocytes to kill intracellular bacteria. Decreased intracellular killing of E. coli by granulocytes containing either B. fragilis or S. aureus is due to the limited killing capacity of granulocytes. These interactions between E. coli and B. fragilis or S. aureus found for phagocytosis and intracellular killing were also observed in in vivo studies: in an experimental thigh lesion infection in mice, E. coli showed stronger proliferation after coinoculation with B. fragilis or with S. aureus than after injection of E. coli alone. These in vitro and in vivo findings indicate that bacterial interactions, not only between aerobic and anaerobic bacteria but also between two species of aerobic microorganisms, compete for host defense mechanisms (i.e., opsonization, phagocytosis, and intracellular killing).     

Human fibronectin binding to staphylococcal surface protein and its relative inefficiency in promoting phagocytosis by human polymorphonuclear leukocytes, monocytes, and alveolar macrophages.

The interaction between human fibronectin and 17 strains of staphylococci was studied in an attempt to elucidate the staphylococcal cell wall component(s) involved in fibronectin binding and to determine the influence of fibronectin upon phagocytosis by three types of phagocytic cells. Purified, radiolabeled fibronectin bound to a similar degree to six laboratory strains and three fresh clinical isolates of Staphylococcus aureus; similar binding of fibronectin was found with S. aureus strains deficient in cell wall teichoic acid or clumping factor and coagulase, as well as with three strains of S. epidermidis. There was minimal binding of fibronectin to encapsulated S. aureus and to Escherichia coli. Fibronectin bound to intact cells and to a crude cell wall preparation of S. aureus H, but not to purified cell walls or peptidoglycan. Trypsinization of staphylococci prevented subsequent fibronectin binding, but binding did not correlate well with the protein A content in S. aureus cell walls. At physiological concentrations, fibronectin binding to staphylococci did not promote phagocytosis of bacteria by human polymorphonuclear leukocytes, monocytes, or alveolar macrophages. Also, depletion of fibronectin from normal human serum did not result in a measurable loss of opsonic activity for staphylococci. It is concluded that fibronectin binding to staphylococci involves a surface protein shared among strains of S. aureus and S. epidermidis, and that in comparison to C3b and IgG, fibronectin plays a relatively minor role as an opsonin for staphylococci.     

Recombinant Brugia malayi pepsin inhibitor (rBm33) induced monocyte function and absence of apoptotic cell death: an in vitro study

The effect of recombinant Brugia malayi pepsin inhibitor (rBm33) on human monocytes/macrophages has been examined using THP-1 cells. THP-1 cells stimulated with rBm33 showed enhanced levels of expression of pro-inflammatory cytokines (IL-1β, TNF-α, IL-6) and diminished levels of IL-12, iNOS and anti-inflammatory cytokine (IL-10) expression suggesting the predominant features of Th1 response. Phorbol-12-myristate-13-acetate (PMA) treated THP-1 cells stimulated with rBm33 and subsequent incubation with GFP expressing Escherichia coli (E. coli) for 2 h enhanced the uptake of E. coli. Nitric oxide (NO) levels measured in the supernatants of these cultures did not show significant changes. Apoptotic studies with Peripheral Blood Mononuclear Cells (PBMCs) from normal individuals stimulated with rBm33 did not induce apoptosis of monocytes or lymphocytes. These observations suggest that rBm33 stimulates macrophages to induce Th1 response and does not promote apoptosis.     

Mechanism of enhanced phagocytic response in protein a treated rat macrophages.

Protein A of S. aureus Cowan I has been shown to stimulate macrophage mediated phagocytosis. The present study was undertaken to understand the mechanism involved in the enhancement of phagocytosis of peritoneal macrophages by protein A. The lucigenin and luminol-dependent chemiluminescence (CL) of rat peritoneal macrophages, after incubation with various concentrations of protein A, flow-cytometric studies using DCFH-DA as a fluorescent compound and phagocytosis of sheep red blood cells (SRBCs) by rat peritoneal macrophages were studied. A significant increase in lucigenin dependent CL due to formation of superoxide anions (O2-.) and in luminol dependent CL due to formation of hydrogen peroxide (H2O2) was observed in protein A treated macrophages. A significant increase in intracellular hydrogen peroxide (H2O2) was also observed along with an increase in phagocytosis of SRBCs by protein A treated macrophages. The present findings indicate that protein A helps to increase phagocytosis and triggers respiratory burst of macrophages. Thus, both increased phagocytic response and respiratory burst of macrophages in protein A treated animals may be contributing to the antitumor property of protein A reported earlier.     

气道上皮细胞对巨噬细胞表型和吞噬功能的影响及HIF-1α的作用

目的:探讨气道上皮细胞对巨噬细胞表型和吞噬活性的影响及缺氧诱导因子1α(HIF-1α)的作用。方法:将不同浓度(0、100、200、400和800μmol/L)氯化钴(CoCl_2)处理或转染HIF-1αsi RNA的人支气管上皮(HBE)细胞与12-肉豆蔻酸13-乙酸佛波酯(PMA)诱导人单核细胞系THP-1分化的巨噬细胞共培养,RT-qPCR检测HBE细胞HIF-1α的m RNA表达,流式细胞术检测巨噬细胞表面标志物的表达及对大肠杆菌的吞噬率。结果:CoCl_2浓度依赖性增加HBE细胞HIF-1α的m RNA表达,8 h为峰值,同时CoCl_2处理的HBE细胞也增加共培养的巨噬细胞CCL3、CD163、CD206和CCL18荧光强度比率,800μmol/L处理的HBE细胞作用最强;共培养8 h和12 h的巨噬细胞CCL3荧光强度比率增加最明显,而共培养24 h的巨噬细胞CD163、CD206和CCL18荧光强度比率上升更明显。转染HIF-1α-Homo-488 si RNA的HBE细胞对巨噬细胞CCL3、CD163、CD206和CCL18的刺激作用明显减弱。与不同浓度CoCl_2处理的HBE细胞共培养24 h的巨噬细胞对大肠杆菌的吞噬率最初(60 min以前)均呈不同的上升趋势,其后吞噬率均降低。相对于正常HBE细胞共培养组,400和800μmol/L刺激组在各时点的吞噬率均降低,其中800μmol/L刺激组降低最明显。结论:低氧环境下气道上皮细胞早期增强巨噬细胞向M1优势转化,而长期低氧作用的气道上皮细胞抑制巨噬细胞吞噬作用并向M2优势转化,HIF-1α可能是这些过程的重要介质。     

人类新细胞因子(CKLF-1)在大肠杆菌中的表达与鉴定

目的：进一步研究人类新细胞因子－－趋化素样因子1（CKLF－1）蛋白的结构与生物学活性。方法：构建了融合蛋白的原核表达质粒，并在大肠杆菌中进行诱导表达，获得了原核表达的融合蛋白，经凝血酶切割获非融合重组蛋白，并进行体外活性鉴定。结果：CKLF－1原核表达蛋白获得了高表达，纯化后获得约90％纯度以上蛋白，发现其可以与肝素结合，生物学活性检测表明其对人中性粒细胞，外周血单个核细胞和大鼠的巨噬细胞具有明显的趋化作用。结论：CKLF－1原核表达蛋白具有与真核表达蛋白类似的生物学活性。