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PubMed1997

Purification and binding properties of a human ficolin-like protein.

Ficolin was initially identified from porcine uterus as a TGF-beta 1 binding protein and is considered to have an overall structure similar to that of the complement protein C1q and the collectins. Recent studies have shown that human ficolin is synthesized mainly by monocytes in peripheral blood and that it could potentially bind to sugar structures on microorganisms. The aim of the present investigations was to isolate ficolin from human plasma by affinity chromatography on immobilized sugars. A human serum protein was identified in the GlcNAc eluate from GlcNAc-Sepharose which migrated as a polypeptide of approx. 40 kDa on SDS-PAGE under reducing conditions and was, after further purification by FPLC on a mono-Q column, shown to have an identical N-terminal sequence, over the first 14 residues, to P35, a plasma protein having similar sequence and domain organisation to ficolin. This protein, named the ficolin-like protein, was shown to be sensitive to collagenase and similar to P35 in that it was also disulphide-linked into an oligomer of approx. 320 kDa. However, unlike P35, its binding to GlcNAc was independent of Ca2+. Gel-filtration studies showed that this ficolin-like protein also had a molecular weight of approx. 320 kDa under non-dissociating conditions. During the course of this study this ficolin-like protein was found to simply bind to CNBr-activated Sepharose which had been inactivated with Tris, and from which it could be eluted with GlcNAc. This ficolin-like protein was also shown to bind to GlcNAc, but not to mannose and maltose. The functional significance of the unusual binding property of this ficolin-like protein is not clear, but it has facilitated the development of a simple method for its purification.

Acetylglucosamine↗
PubMed1984

Stereospecific binding capacity of proteins on surfaces--simple mathematical models.

The adsorption of and interaction between protein molecules on solid surfaces are phenomena involved in many situations of biochemical and physical interest. This communication is an attempt to relate stoichiometrically substances binding to each other on surfaces. One experimental observation, which we try to explain, is that the maximum antibody binding capacity of an antigen covered surface does not always occur at the largest coverage of antigens.

Adsorption↗
PubMed1985

Circulating immune complexes and immunosuppressive acidic protein in patients with renal cell carcinoma.

Sera from 23 patients with renal cell carcinoma were tested for circulating immune complexes by Clq binding assay and immunosuppressive acidic protein by single radial immunodiffusion. The mean values of circulating immune complexes and immunosuppressive acidic protein in the patients were significantly higher than those of normal controls, and over-all positive rates were 52 and 35 per cent, respectively. There was a significant correlation between immunosuppressive acidic protein levels and the extent of tumor invasion. Immunosuppressive acidic protein may be a more useful marker than circulating immune complexes. However, presently synthetic evaluations of patients with various nonspecific markers, including these 2 factors, will be necessary.

Adult↗
PubMed1983

Immune complex assays in rheumatic diseases.

A wide variety of antigen-nonspecific immune complex assays have been developed in recent years for the detection and quantitation of immune complexes in pathologic fluids. These assays detect complexed antibody regardless of the antigen involved. Almost all of these assays use biologic reagents that may react with substances other than complexed antibody. In addition, the assays do not differentiate nonspecifically aggregated antibody from antigen-complexed antibody. Hence, these assays are not absolute tests for immune complexes. On the basis of studies using these assays, "immune complexes" have been detected in a large number of rheumatic diseases. While these findings have been of considerable investigative interest, thus far they have been of little practical clinical utility. The detection of immune complexes has not been shown to be essential in any clinical conditions but may be helpful in monitoring disease activity in systemic lupus erythematosus (SLE) and may provide useful diagnostic information in two rare syndromes, Lyme arthritis and SLE-related syndrome.

Antigen-Antibody Complex↗
PubMed2003

By binding SIRPalpha or calreticulin/CD91, lung collectins act as dual function surveillance molecules to suppress or enhance inflammation.

Surfactant proteins A and D (SP-A and SP-D) are lung collectins composed of two regions, a globular head domain that binds PAMPs and a collagenous tail domain that initiates phagocytosis. We provide evidence that SP-A and SP-D act in a dual manner, to enhance or suppress inflammatory mediator production depending on binding orientation. SP-A and SP-D bind SIRPalpha through their globular heads to initiate a signaling pathway that blocks proinflammatory mediator production. In contrast, their collagenous tails stimulate proinflammatory mediator production through binding to calreticulin/CD91. Together a model is implied in which SP-A and SP-D help maintain a non/anti-inflammatory lung environment by stimulating SIRPalpha on resident cells through their globular heads. However, interaction of these heads with PAMPs on foreign organisms or damaged cells and presentation of the collagenous tails in an aggregated state to calreticulin/CD91, stimulates phagocytosis and proinflammatory responses.

Animals↗
PubMedDate not supplied

A precerebellin-like protein is part of the acute phase response in rainbow trout, Oncorhynchus mykiss.

The acute phase response (APR) has a long evolutionary history, but it remains to be characterized fully in lower vertebrates. To study the acute phase proteins of a teleost, rainbow trout (Oncorhynchus mykiss), we induced an APR by injecting Vibrio bacterin emulsified in FIA. In samples taken over the next 3 weeks, the total plasma protein profile changed consistently as seen in one and two-dimensional SDS PAGE. One 18.1 kD upregulated protein was isolated from 2D gels and an N-terminal sequence obtained. Using reverse transcriptase-PCR, a 700 bp cDNA sequence was amplified. The sequence is 53% similar at the amino acid level with rat precerebellin (regions aa 42-184 from trout and aa 89-224 precerebellin), and 46% similar with the globular portion of the human B chain of the first complement component C1q. However, it lacks the collagen portion of C1q with its characteristic Gly-X-Y repeats. The isolated protein seems to be involved in the inflammatory response but its physiological function is unknown.

Acute-Phase Proteins↗
PubMed2002

Immune response gene expression increases in the aging murine hippocampus.

Using GeneChips, basal and lipopolysaccharide (LPS)-induced gene expression was examined in the hippocampus of 3-, 12-, 18- and 24-month-old male C57BL/6 mice to identify genes whose altered expression could influence hippocampal function in advanced age. Gene elements that changed with age were selected with a t-statistic and specific expression patterns were confirmed with real-time quantitative PCR. Basal expression of 128 gene elements clearly changed with age in the hippocampus. Fourteen gene elements showed increased expression with age and these increases were validated after LPS stimulation. Major histocompatibility complex (MHC) TL region and thymic shared antigen (TSA-1) gene expression increased, suggesting T cell activation in the hippocampus with age. Cytokine (interleukin (IL)-1beta, tumor necrosis factor (TNF)-alpha) and chemokine (macrophage chemotactic protein-1) expression increased sharply in 24-month-old mice. These findings are in contrast to a decrease in the peripheral immune response, documented by decreased T cell proliferation and decreased ratios of naive to memory T cells. Age-related increases in inflammatory potential in the brain may contribute to neurodegenerative diseases of the aged.

Aging↗
PubMed1994

Enhancement of HBsAg detection in serum of patients with chronic liver disease following removal of circulating immune complexes.

Patients with chronic liver disease and hepatocellular carcinoma may lack serological evidence of previous hepatitis B virus infection. The purpose of the present study was to test the hypothesis that circulating immune complexes may interfere with the detection of low levels of HBsAg in such patients. Sera from 190 patients were initially screened for the presence of circulating immune complexes. Patients belonged to three clinical categories: asymptomatic HBsAg carriers (50 patients), chronic liver disease (30 patients) and hepatocellular carcinoma (110 patients). Forty-one of the group of 190 patients (21%) were positive for circulating immune complexes. Sera from 21 patients were selected for further evaluation. The sera of 13 chronic liver disease or hepatocellular carcinoma patients (HBsAg negative, hepatitis B virus-DNA negative, with or without evidence of previous hepatitis B virus infection) and eight HBsAg positive carriers (four asymptomatic, three with chronic liver disease and one with hepatocellular carcinoma) were passed through a Clq affinity column (first column) to remove circulating immune complexes. Unbound material was then passed through a monoclonal IgG2a anti-HBs affinity column (second column). Unbound material (following both columns) contained free HBsAg, as determined by monocolonal radio-immunoassay, in eight patients in whom HBsAg had been undetectable in the original serum. Removal of circulating immune complexes from the serum of the three HBsAg positive patients with chronic liver disease also caused a significant increase in measurable circulating HBsAg compared with the original serum.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2000

Enhanced levels of scrapie responsive gene mRNA in BSE-infected mouse brain.

The expression of the mRNA of nine scrapie responsive genes was analyzed in the brains of FVB/N mice infected with bovine spongiform encephalopathy (BSE). The RNA transcripts of eight genes were overexpressed to a comparable extent in both BSE-infected and scrapie-infected mice, indicating a common series of pathogenic events in the two transmissible spongiform encephalopathies (TSEs). In contrast, the serine proteinase inhibitor spi 2, an analogue of the human alpha-1 antichymotrypsin gene, was overexpressed to a greater extent in the brains of scrapie-infected animals than in animals infected with BSE, reflecting either an agent specific or a mouse strain specific response. The levels of spi 2 mRNA were increased during the course of scrapie prior to the onset of clinical signs of the disease and the increase reached 11 to 45 fold relative to uninfected controls in terminally ill mice. Spi 2, in common with four of the other scrapie responsive genes studied, is known to be associated with pro-inflammatory processes. These observations underline the importance of cell reactivity in TSE. In addition, scrg2 mRNA the level of which is enhanced in TSE-infected mouse brain, was identified as a previously unrecognized long transcript of the murine aldolase C gene. However, the level of the principal aldolase C mRNA is unaffected in TSE. The increased representation of the longer transcript in the late stage of the disease may reflect changes in mRNA processing and/or stability in reactive astrocytes or in damaged Purkinje cells.

Animals↗
PubMed1998

Structural aspects of collectins and receptors for collectins.

The collectins are oligomeric molecules composed of C-type lectin domains attached to collagen regions via alpha-coiled neck regions. Five members of the collectins have been characterized. Mannan-binding lectin (MBL), conglutinin and collectin-43 (CL-43) are serum proteins produced by the liver. Lung surfactant protein A (SP-A) and lung surfactant protein D (SP-D) are mainly found in the lung, where they are synthesized by alveolar type II cells and secreted to the alveolar surface. The collectins are believed to play an important role in innate immunity. They bind oligosaccharides on the surface of a variety of microbial pathogens. After binding of the collectins to the microbial surface effector mechanisms such as agglutination, neutralizing or opsonization of the microorganisms for phagocytosis are initiated. SP-A and SP-D stimulate chemotaxis of phagocytes and once bound to the phagocytes, the production of oxygen radicals can be induced. In the case of MBL the opsonization can be further enhanced by complement activation via the MBLectin pathway while conglutinin interacts with the complement system by binding to the complement degradation product iC3b. A number of receptors and binding molecules interacting with the collectins are found on the membrane or in association with the membrane of various cells responsible for phagocytosis and clearance of microorganisms. This paper focus on the structural aspects of the collectins and the receptors for collectins.

Amino Acid Sequence↗
PubMed1986

Primary idiopathic cutaneous pustular vasculitis.

Pustular cutaneous vasculitis results from a heterogeneous group of disorders characterized by pustules on purpuric bases. Although the cause of this group of conditions is diverse, the histopathologic picture of the lesions is the same, showing a Sweet's-like or leukocytoclastic vasculitis. These distinctive lesions may occur in patients with Behçet's syndrome, bowel-associated dermatosis-arthritis syndrome, or chronic gonococcemia. We describe, for the first time, a patient with primary idiopathic cutaneous pustular vasculitis. This patient had evidence of both circulating immune complexes and serum enhancement of neutrophil migration. Extensive evaluation failed to reveal any underlying systemic disease. A classification of the pustular vasculitides is proposed.

Adolescent↗
PubMed2001

Renal transplantation in a patient with hypocomplementemic urticarial vasculitis syndrome.

We describe a 36-year-old man who presented with hypocomplementemic urticarial vasculitis syndrome (HUVS) with severe renal involvement. Despite steroid therapy, the patient developed end-stage renal disease (ESRD) leading to chronic hemodialysis therapy. Renal transplantation was performed after hemodialysis therapy (secondary), and the patient developed a typical HUVS relapse 9 months after transplantation despite conventional immunosuppressive therapy that was successfully treated with plasma exchange. This case shows for the first time that HUVS can induce severe renal involvement responsible for ESRD and that HUVS can relapse after renal transplantation. It also suggests that plasma exchange therapy may be of value for rapidly controlling the clinical symptoms.

Adult↗
PubMed1986

Detection of circulating immune complexes in the sera of dogs infected with Dirofilaria immitis, by Clq-binding enzyme-linked immunosorbent assay.

The presence of circulating immune complexes (CIC) in the sera of dogs infected with Dirofilaria immitis was detected by using a Clq-binding enzyme-linked immunosorbent assay. Specificity of this assay with different concentrations of heat-aggravated canine IgG (ACG) was observed, i.e., the ELISA readings, expressed as microgram equivalents ACG/ml, increased with increasing amounts of ACG. The intra-assay variability was below 10%. The CIC levels of infected and uninfected dogs were 177.0 +/- 104.7 micrograms/ml and 22.8 +/- 45.8 micrograms/ml (mean +/- SD), respectively. The highest level was observed in 12 dogs with amicrofilaraemic infection. Age distribution of CIC levels in the 23 infected dogs also showed a significant positive correlation. These findings suggested that the CIC are present in the sera of dogs with dirofilariasis and may relate to canine glomerulonephritis.

Age Factors↗
PubMed2003

Innate immunity and brain inflammation: the key role of complement.

The complement inflammatory cascade is an essential component of the phylogenetically ancient innate immune response and is crucial to our natural ability to ward off infection. Complement is involved in host defence by triggering the generation of a membranolytic complex (the C5b-9 complex) at the surface of the pathogen. Complement fragments (opsonins; C1q, C3b and iC3b) interact with complement cell-surface receptors (C1qRp, CR1, CR3 and CR4) to promote phagocytosis and a local pro-inflammatory response that, ultimately, contributes to the protection and healing of the host. Complement is of special importance in the brain, where entrance of elements of the adaptive immune system is restricted by a blood-brain barrier. There is now compelling evidence that complement is produced locally in response to an infectious challenge. Moreover, complement biosynthesis and activation also occurs in neurodegenerative disorders such as Alzheimer's, Huntington's and Pick's diseases, and the cytolytic/cytotoxic activities of complement are thought to contribute to neuronal loss and brain tissue damage. However, recent data suggest that at least some of the complement components have the ability to contribute to neuroprotective pathways. The emerging paradigm is that complement is involved in the clearance of toxic cell debris (e.g. amyloid fibrils) and apoptotic cells, as well as in promoting tissue repair through the anti-inflammatory activities of C3a. Knowledge of the unique molecular and cellular innate immunological interactions that occur in the development and resolution of pathology in the brain should facilitate the design of effective therapeutic strategies.

Animals↗
PubMed1984

Bovine conglutinin is a collagen-like protein.

Conglutinin is a bovine plasma protein which is relatively large and asymmetric with elevated contents of glycine and, to some extent, proline. Although its physiologic function is unknown, conglutinin is known to bind, in the presence of calcium, to yeast cell walls and to the solid-phase-inactivated third component of complement. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions, isolated conglutinin appeared to consist of a single polypeptide chain (Mr 48 000). Unreduced conglutinin consisted of a single stained band with an apparent molecular weight of approximately 300 000. Cross-linking experiments with glutaraldehyde and dimethyl suberimidate suggested that this Mr 300 000 molecule consists of six of the disulfide-linked polypeptide chains. Amino acid composition revealed hydroxylysine and hydroxyproline together with elevated glycine and proline contents. Digestion of reduced, alkylated conglutinin with bacterial collagenase resulted in formation of a precipitate which consisted of an Mr 24 000 peptide which was digested to Mr 21 000 with large quantities of collagenase. These peptides contained less glycine, proline, hydroxylysine, and hydroxyproline than did the intact protein. The supernatant from this digestion mixture was, however, enriched in these four amino acids, with glycine making up nearly one-third of the total. Prolonged digestion with pepsin at 37 degrees C resulted in an Mr 20 000 peptide which was enriched in glycine, proline, hydroxyproline, and hydroxylysine. Amino-terminal sequence analysis showed that the glycine-X-Y repeating sequence begins at residue 26.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗