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PubMed1989

Molecular cloning and characterization of the novel, human complement-associated protein, SP-40,40: a link between the complement and reproductive systems.

The cDNA sequence encoding the human complement-associated protein, SP-40,40, is reported. The two chains of SP-40,40 are coded in a single open reading frame on the same mRNA molecule, indicating the existence of a biosynthetic precursor protein which matures post-synthetically by the proteolysis of at least one peptide bond. The precursor is preceded by a signal sequence for vectorial export and contains six N-linked glycosylation sites distributed equally between the two chains of the structure. The sequence of the SP-40,40 precursor bears a 77% identity to a rat sulphated glycoprotein-2 (SGP-2) which is the major secreted product of Sertoli cells. The presence of SP-40,40 within human seminal plasma at levels comparable to those in serum was demonstrated, indicating that SP-40,40 and SGP-2 are serum and seminal forms of the same protein. A sequence of 23 amino acids within the beta-chain of SP-40,40 exhibited significant homology to corresponding segments located within complement components C7, C8 and C9. The short cysteine-containing motif represented the only evidence of a possible vestigial relationship between SP-40,40 and other complement components. The precise role of SP-40,40 is not known in either blood or semen but the present findings document an intriguing link between the immune and the reproductive systems.

Amino Acid Sequence↗

PubMed1992

Antibodies to meningococcal class 1 outer membrane proteins in South African complement-deficient and complement-sufficient subjects.

Inhibition assays were used to investigate human serum antibodies to the meningococcal class 1 outer membrane proteins. We adapted the whole-cell enzyme-linked immunosorbent assay technique to determine the ability of sera to inhibit the binding of murine subtyping monoclonal antibodies. Serum samples from 33 South African subjects with a deficiency in the sixth component of complement as well as serum samples from various groups of complement-sufficient subjects were investigated. Subjects were subdivided according to whether they were (i) convalescent from Neisseria meningitidis infections, (ii) nonconvalescent, or (iii) controls. Preliminary subtyping investigations had shown that P1.2 was present on 36% of meningococcal clinical isolates from Cape Province, South Africa. Assays with the anti-P1.2 antibodies showed the presence of high antibody levels in many deficient sera and moderately elevated levels in some sera from the complement-sufficient convalescent patients. P1.2, P1.4, P1.15, and P1.16 are epitopes situated on loop 4 of the class 1 outer membrane proteins, whereas P1.7 is on loop 1. Inhibition assays showed that human sera that inhibited binding by P1.2 monoclonal antibodies tended to inhibit the other monoclonal antibodies directed to loop 4 epitopes. This suggests that the epitopes recognized by the human antibodies are not exactly the same as the epitopes recognized by the murine monoclonal antibodies and raises the possibility of the importance of other epitopes.

Antibodies, Bacterial↗

PubMed1989

The complement profile in clinical medicine. Inherited and acquired conditions lowering the serum concentrations of complement component and control proteins.

The serum complement profile of patients with systemic or discoid lupus erythematosus, synovitis, vasculitides, certain recurrent or chronic skin rashes, recurrent or fulminant infections, particularly with Neisseria, may reveal homozygous deficiencies of complement components causally related to the illness. The nephritis of systemic lupus erythematosus (SLE) is often accompanied by a distinctive complement profile which indicates classical pathway activation and which can be used as an index of the success of treatment. In membranoproliferative glomerulonephritis (MPGN), the hypocomplementemia may reflect classical pathway activation in type I, the nephritic factor of the amplification loop in type II, or a nephritic factor activating terminal components in type III. In acute poststreptococcal glomerulonephritis, the cause of the hypocomplementemia is not known but the profile usually differs from that of MPGN or SLE. In these acquired hypocomplementemias, the profile supplements the renal biopsy in providing diagnostic information.

Biomarkers↗

PubMed1986

Antigenic crossreactivity of the alpha subunit of complement component C8 with the cysteine-rich domain shared by complement component C9 and low density lipoprotein receptor.

Complement component C9 contains two distinct cysteine-rich domains exhibiting high sequence resemblance to a domain present in the low density lipoprotein (LDL) receptor and epidermal growth factor precursor, respectively. Antibodies were raised against a peptide corresponding to the most conserved region of the LDL receptor/C9-homology segment. The antibodies were shown by immunoblotting to bind specifically to C9 but also to crossreact with C8 alpha, the alpha subunit of complement component C8. Moreover, a monoclonal antibody to a neoantigen present in polymerized C9 bound to an epitope exposed on C8 within the C5b-8 complex but buried in monomeric C8, suggesting that C8 and C9 undergo similar conformational changes during membrane-attack-complex assembly. Isolated C8 alpha-gamma exhibited the propensity to polymerize in the presence of Zn2+ and urea, as already demonstrated for C9. These data indicate that C8 alpha is closely related, both structurally and functionally, to C9.

Complement C8↗

PubMed1975

Interaction of collagen with serum complement: inhibition of complement-mediated hemolysis.

Collagens from various vertebrate tissues were tested for their ability to consume complement (C) activity upon incubation in human serum or with isolated components of complement. 10 of 12 collagens tested had anticomplementary activity. The heat-denatured form of collagen, gelatin, was found weakly anticomplementary, but elastin was found inactive in the interaction with C. Inactivation of C is a reaction which is dependent on the time of incubation and the collagen concentration and partially dependent on the temperature of incubation. Most collagens depleted C from human serum in presence of cation chelators, EDTA and EGTA, whereas the large part of anticomplementary activity of soluble collagens obtained from rat skin was abolished in presence of EDTA. Evidence is presented that two different principles in collagens play a role in inactivation of C. A factor, contained in insoluble collagens and inhibitable by mild oxidation with periodate, inactivates C1 directly even in presence of chelating agents. Another principle, contained in soluble and insoluble collagen and resistant to periodate treatment, depletes C in serum by utilization of C via the alternate pathway (the C3 shunt).

Animals↗

PubMed1991

Low number of complement C3b/C4b receptors (CR1) on erythrocytes from patients with essential mixed cryoglobulinemia, systemic lupus erythematosus and rheumatoid arthritis: relationship with disease activity, anticardiolipin antibodies, complement activation and therapy.

Our aim was to assess whether the amount of complement C3b/C4b receptors (CR1) on erythrocytes shows a correlation to disease activity in various connective tissue diseases such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA) and essential mixed cryoglobulinemia (EMC). Using an anti-CR1 monoclonal antibody, 26 patients with SLE, 34 with RA and 22 patients with EMC were investigated for erythrocyte CR1 expression. The control group consisted of 30 healthy individuals. The mean number of CR1/erythrocyte in the control group was 568 +/- 197 (range 174-1060), significantly higher than studied (EMC:379 +/- 248; p = 0.0005;SLE 147 +/- 56, p less than 0.0001; RA 298 +/- 177, p less than 0.0001). In patients with RA and in SLE, but not in patients with EMC, the number of CR1 numbers and anticardiolipin antibody (aCl) titers (r2 = 0.493; p = 0.034). A statistically significant correlation between CR1 numbers and CH50 values was found in patients with SLE, while in 3 patients with RA 4 months of therapy with cyclosporine A led to a further 30% reduction in CR1 number. Our conclusions are that (a) the decreased expression of erythrocyte CR1 is apparently a common feature of patients with various connective tissue diseases; (b) several acquired factors such as disease activity, complement activation, aCl and drugs may contribute to the loss of CR1 from erythrocytes; (c) in patients with RA and SLE, but not in patients with EMC, CR1 enumeration on erythrocytes may serve as a variable for clinical monitoring.

Adult↗

PubMed1990

Hormonal regulation of complement biosynthesis in human cell lines--II. Upregulation of the biosynthesis of complement components C3, factor B and C1 inhibitor by interleukin-6 and interleukin-1 in human hepatoma cell line.

The effect of interleukin (IL)-6 and IL-1 on the biosynthesis of complement components C3, factor B, C2, C4 and C1 inhibitor (C1 inh), as well as that of albumin, was studied in vitro in human hepatoma-derived cell line, HepG2. Measuring the amounts of secreted complement proteins we detected a significant upregulation of C3 by both hormones. The enhancement of the factor B and especially that of C1 inh production was predominant by IL-6. In our experimental system neither IL-1 nor IL-6 affected the biosynthesis of C2 and C4. Albumin secretion was significantly decreased only in the simultaneous presence of IL-1 and IL-6. Detection of the changes in the amounts of C3- and factor B-specific mRNA of HepG2 cells suggests a pretranslational regulation by these cytokines. The secretion of C3 and factor B was markedly potentiated when IL-1 and IL-6 were added together. However only the gene expression of factor B, but not of C3, was found to reveal synergism. IL-6 enhanced the in vitro production of C3 in mouse hepatocytes as well. This effect was greatly potentiated in the presence of histamine.

Carcinoma, Hepatocellular↗

PubMed1992

Limited tryptic cleavage of complement factor H abrogates recognition of sialic acid-containing surfaces by the alternative pathway of complement.

The potency of complement factor H (H) in accelerating the decay of the alternative pathway C3 convertase, C3b,Bb (decay-accelerating activity), was used as a measure of the affinity of native versus trypsin-treated H for the complement protein C3b bound to surfaces. When about 99% of H was cleaved at the primary tryptic cleavage site 34 kDa from the N-terminus, its decay-accelerating activity on C3b,Bb on sheep erythrocytes fell about 60-fold, whereas the trypsin-treated H was only 3-4 times less potent than native H in dissociating C3b,Bb on Sepharose 4B. The residual decay-accelerating activity, remaining after the primary cleavage, was not affected by secondary cleavage at a site 120 kDa from the N-terminus, as shown with H preparations cleaved to different degrees. Because cell surface sialic acid is known to be responsible for the high affinity of H for C3b bound on sheep erythrocytes, the results strongly suggest that the integrity of the primary tryptic cleavage site of H is essential for the recognition of sialic acid-containing surfaces by the C3b-H complex.

Animals↗

PubMed1979

Complement activation in acne vulgaris: consumption of complement by comedones.

Comedones, the contents of acne lesions, were shown to consume scomplement hemolytic activity in normal serum. This consumption was stimulated by the addition of serum from patients with inflammatory acne. Absorption of acne serum with Propionibacterium acnes cells removed all stimulating activity. Immunoelectrophoretic analysis of serum incubated with comedones revealed the conversion of C3 and factor B in normal serum. The addition of acne serum resulted in cleavage of C4. In serum treated with ethylene glycol-bis(beta-aminoethyl ether)-N,N'-tetraacetic acid, only C3 and factor B were converted. This indicates that comedones may activate complement by either the classical or the alternative pathway. It is suggested that P. acnes cells in comedonal material are responsible for the complement activation.

Acne Vulgaris↗

PubMed1975

Studies on rat complement. II. Complement level in experimental tumor in rats.

In the course of methylcholanthrene induced carcinogenesis in rats, CIA50, C4 and C3 increased as compared with control and correlation of tumor size with increase in CIA50, C4 and C3 was observed. In the course of dimethylaminoazobenzen carcinogenesis of rats, complement level and C3 level decreased but in splenectomized rats fed by dimethylaminoazobenzen showed elevated level of complement system. After Corynebacterium infection, CIA50 and C3 of rats increased. This phenomenon is considered to be one of the essential factors to induce high resistance against tumor inoculation.

Animals↗

PubMed1991

Complement activation and bioincompatibility. The terminal complement complex for evaluation and surface modification with heparin for improvement of biomaterials.

The degree of biocompatibility of biomaterials can be evaluated using various assay systems detecting activation of the blood cascade systems, leukocytes or platelets. Activation of complement is one mechanism associated with adverse effects observed when bioincompatible materials are used. We present data showing that the terminal complement complex, an indicator of terminal pathway activation, is suitable for evaluation of biocompatibility of biomaterials such as cardiopulmonary bypass devices. Furthermore, our results suggest that bioincompatibility is improved when artificial surfaces are modified with end point attached functionally active heparin.

Complement Activation↗

PubMed1977

Complement system in human colostrum: presence of nine complement components and factors of alternative pathway in human colostrum.

Evidence has been obtained for the presence in human colostrum of all nine components of complement (C), C1 through C9, and factors of the alternative pathway. Samples of colostrums collected from five women at 1-4 days after normal parturition were assayed for the haemolytic activities of individual components. As compared with normal human sera, the activities of each component ranged from 0.03 to 7% of those in sera. The activities of C4, C7 and C9 were relatively high, while that of C1 was extremely low. In most of the cases, the activities of individual components gradually increased following delivery, when expressed as the activity per unit weight (g) of protein in the colostrum. When the colostrums were treated with cobra venom factor, most of the colostrums showed 10-20% reduction in the C3 activity. This finding indicates the presence of factors such as B and D which are involved in the activation of C through the alternative pathway. The role as a defense factor of the C system in human colostrum and milk is discussed in connection with the ability of secretory IgA to react with C.

Colostrum↗

PubMed1979

CELISA (complement-enzyme linked immuno sorbent assay) a new method for the estimation of complement fixing antibodies; its use for Chagas' disease.

A description is given of a new method for the estimation of complement fixing antibodies. This is a modification of the Enzyme Linked Immuno Sorbent Assay (ELISA) to a Complement-Enzyme Linked Immuno Sorbent Assay (CILISA) using an anti-C3 conjugate. The method is independent of the haemolytic system. To test the sensitivity of CELISA, comparative studies were carried out with the Haemolytic Complement Fixation Test (CFT), indirect haemagglutination test and ELISA with sera from patients with Chagas' Disease. The results with CELISA showed significant correlations with CFT titers whereas no correlations were observed with the other serological tests.

Antibodies↗

PubMed1989

Regulation of human and murine complement: comparison of 5' structural and functional elements regulating human and murine complement factor B gene expression.

The serine protease complement factor B (Bf), an acute phase plasma protein, is a component of the alternative pathway of complement activation. Previous studies revealed that several cytokines including IFN-gamma and IL-1 are involved in mediating acute phase Bf expression. To determine the molecular details of Bf expression we isolated, sequenced and characterized the 5' flanking regions of the human and murine Bf genes. In both species the Bf transcriptional start site in liver was located less than 400 bp 3' to the polyadenylation site of the upstream C2 gene. This upstream intergenic region contained greater than 65% nucleotide homology between species. Within this region, an IRS and three heat shock consensus elements were found in the murine sequence in an identical position to that of the human. To examine the functional details of Bf expression, a series of mouse and human Bf promoter-chloramphenicol acetyltransferase (CAT) chimeric gene constructs were transfected into mouse L or human HepG2 cells. Analysis of expression of these fusion gene constructs revealed that 1) cis-acting DNA sequences identified, at least in part, in the 3' untranslated region of the C2 gene (within the 400 bp upstream of the Bf cap site) mediate responsiveness to IL-1 and IFN-gamma, 2) the responsiveness to each mediator appears to be conferred by separate upstream regions similar in position and homologous in man and mouse, and 3) the IL-1 responsive region in both species appears to have the characteristics of an enhancer element. The results of this analysis suggest a selective pressure to conserve the intergenic sequence between C2 and Bf genes and that further studies of these sequences will be useful in elucidating mechanisms controlling the acute phase response.

Animals↗

PubMed1975

Studies on complement-fixation reaction in equine infectious anemia. II. Identification of complement-fixing inhibitors.

The substances responsible for inhibiting complement-fixation (CF) reaction of the late-stage serum of an equine infectious anemia (EIA)-infected horse were investigated. It was found that the IgG and IgG(T) classes in the late-stage serum were responsible for the CF inhibition. IgA could not be detected in partially purified IgG(T) by an immunodiffusion test using rabbit anti-human IgA serum. Other serum components could not be demonstrated in purified IgG by immunoelectrophoresis using rabbit anti-horse serum. The IgG class simultaneously showed CF and CF-inhibiting (CFI) activities, whereas the IgG(T) class showed only CFI activity. The IgG(T) class could exert CFI activity only when it had been reacted with the EIA antigen before addition of the reference CF serum and complement. In contrast, the IgG class converted the CF-active reference serum into a non-CF-reactive one irrespective of whether it was simultaneously reacted with the EIA antigen and the reference CF serum, whether it was added to the reaction mixture of the EIA antigen and the reference CF serum, or whether it was sensitized with the EIA antigen before addition of the reference CF serum. Inhibitory activities of the IgG and IgG(T) classes seemed to be different from each other in their reaction pattern as far as tested under our experimental conditions. Their CFI activities seemed to be specific for EIA, being negative in CFI activity in reaction with other antigens.

Animals↗

PubMed1990

S protein binds to serum-treated agarose beads independently of complement activation and the formation of the terminal complement complex on the beads.

Comparison of initial (early-phase) and terminal (late-phase) sequence activation of complement by agarose beads and endotoxin was evaluated in an enzyme immunoassay (EIA) of serum levels of C3c and C9 neoepitopes, respectively. EIA and Western blotting with anti-S protein monoclonal antibody revealed lower S protein values and weaker S protein bands in serum activated by agarose beads than by endotoxin, implying that S protein was removed from serum by binding to agarose. The binding of S protein to the beads was confirmed by radioimmunoassay and was found to be equal in normal and heat-inactivated serum. In contrast, the terminal complement complex was formed only on agarose beads incubated with normal serum and not with inactivated serum.

Blood Proteins↗

PubMed1977

Complement (C5-a)-induced granulocyte aggregation in vitro. A possible mechanism of complement-mediated leukostasis and leukopenia.

Activated plasma complement will induce biphasic aggregation of human granulocytes dectable by standard nephelometric techniques. The responsible active component was suggested to be C5a by molecular weight and heat-stability assays; moreover, aggragating activity was ablated by anti-C5 but not anti-C3 antibodies. C5a prepared by trypsinization of purified C5 reproduced the aggregating activity of whole activated plasma, whereas plasma from a C5-deficient donor did not support aggregation. Embolization of granulocyte aggregates might be a previously unsuspected cause of leukostasis and pulmonary damage in various clinical situations where intravascular complement activation occurs.

Cell Aggregation↗

PubMed1975

Complement inhibitor(s) released by leukocytes. I. Pretreatment of sheep erythrocytes with supernatants of mouse spleen and thymus cells inhibit whole complement activity and C2 utilization.

Sheep erythrocytes pretreated with supernatants of mouse spleen or thymus cells become resistant to lysis by guinea pig complement. The inhibitory activity (IA) reduces the utilization of C2 by EAC14. Because IA binds to the surface of sheep erythrocytes and does not inhibit C1 irreversibly, it is probably a hitherto undescribed inhibitor of complement.

Animals↗