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PubMed1975

Cyanate as an inactivator of complement proteins.

Sodium cyanate added to normal human serum or serum from patients with sickle-cell disease resulted in the functional inactivation of C3, C5, C6, C7, and the C3b inactivator, but not C8 and C9. Final concentrations as low as 0.5 mM in serum caused inactivation of 12 to 64% of the C3 after 8 hr at 37 degrees C. The activity of the inactivated C3, C5, and C3b inactivator was not restored by dialysis. Most of the functional activity of C3 in cyanate-treated sera was destroyed by very small quantities of 14C-labeled cyanate that was bound to the protein. C3 inactivation by cyanate occurred in heated sera (50 degrees C, 30 min) and sera treated with EDTA, probably indicating that one mechanism for inactivation was by a direct carbamylation reaction. Both C3 and C5 showed two anodal-migrating forms in two dimensional antigen-antibody crossed electrophoresis in some sera treated with low concentrations of cyanate. Measurements of circular dichroism of highly purified carbamylated C3 showed no detectable changes in structure even though most of the functional activity was destroyed. Purified, inactive C3 that was carbamylated with 14C-labeled cyanate was capable of binding to EAC142, but the resulting EAC1423 was weakly positive for immune adherence and negative for agglutination with anti-C3 antiserum. Unlabeled, cell-bound C3b on EAC142 was not susceptible to cyanate action as shown by no loss in immune adherence and positive agglutination with anti-C3 antiserum. The C3b inactivator was more susceptible to cyanate than C3 in a short time period, whereas both were inactivated after 8 hr. Since cyanate is currently being evaluated as a treatment for sickle-cell disease, the inactivation of C3 by the drug is an important consideration for such patients who are already deficient in C3 dependent heat-labile opsonins that aid in host defense.

Anemia, Sickle Cell↗

PubMed1980

The interaction of heparin with plasma proteins. Demonstration of different binding sites for antithrombin III complexes and antithrombin III.

Affinity chromatography of plasma and serum with the use of heparin conjugated Sepharose has confirmed the existence of two types of protein binding sites. A minor heparin fraction binds free AT III selectively and firmly but not its protease complexes. The complexes bind less firmly to another, much larger heparin fraction together with a select group of the plasma proteins at physiological pH and ionic strength. These included complement proteins (C1q, C2, factor B, properdin, and beta 1H), protease inhibitors (inter-alpha-trypsin inhibitor and C3b inactivator) and cell surface proteins (protein HC and fibronectin) as well as beta-lipoproteins. The results demonstrate that affinity chromatography with heparin-Sepharose is extremely useful as an early preparative step in the isolation of these minor plasma components. The results also indicate that the said proteins can be linked to cell surfaces carrying heparinoids in the intercellular space.

Antithrombin III↗

PubMed1982

Reduced alternative complement pathway control protein levels in anorexia nervosa: response to parenteral alimentation.

Serum levels of 16 proteins, including 11 component and control proteins of the complement system were determined before and after nutritional repletion in five female patients with severe malnutrition secondary to anorexia nervosa. Before parenteral alimentation significantly decreased serum levels were found for IgG, IgM, transferrin, Clq, C2, C3, factor B, beta lH, C3b inactivator, properdin, and C4 binding protein. A significant increase in posttreatment serum levels compared with pretreatment levels were found for transferrin, C3, factor B, beta lH, and C3b inactivator. Of the proteins measured, the C3b amplification loop control and component proteins, beta lH, C3b inactivator, C3, and factor B rose to the normal range in response to therapy most rapidly. In the absence of an acute phase reaction, these proteins appear to be particularly good indices of malnutrition and its response to therapy.

Adolescent↗

PubMed1977

Alternative pathway of complement in sickle cell disease.

Thirty-one patients, 10 months to 20 years of age, were studied. A complement abnormality was not identified in sera from patients with sickle cell disease (SCD) by the methods employed in the present study. Concentrations of C3, factor B, total hemolytic activity (CH50), properdin, and C3b inactivator were similar in sera from patients and control subjects (Table 1 and Fig. 2). Although concentrations of C3b inactivator protein were below normal in a few patients, there was no evidence that these levels were low enough to alter the functions mediated by this protein. Initiation of the complement sequence via the alternative pathway by reaction with inulin was equal in patient and control sera when assessed by the activation of factor B, cleavage of C3 and the comsumption of hemolytic complement components (Table 1). Lysis of erythrocytes treated with reduced glutathione was similar in patient and control sera during alternative pathway activation (Fig. 3), indicating comparable formation of lytic complexes via this pathway. An abnormality of the alternative pathway was not detected when the serum from patients with sickle cell disease was reacted with inulin. Thus, this polysaccharide, although commonly empolyed to assess alternative pathway function, is not satisfactory for studying serum from these patients. In addition, activation of the alternative pathway by cobra venom factor was comparable with controls when assessed by the lysis of glutathione-treated erythrocytes.

Adolescent↗

PubMed1970

Studies in vivo and in vitro on an abnormality in the metabolism of C3 in a patient with increased susceptibility to infection.

In a patient with increased susceptibility to infection, lowered serum C3 concentration, and continuously circulating C3b, it was shown that purified (125)I-labeled C3 was converted to labeled C3b shortly after intravenous administration. The fractional catabolic rate of C3 was approximately five times normal at 10% of the plasma pool per hr. The synthesis rate and pool distribution of C3 were normal. Despite this evidence of C3 instability in vivo, no accelerated inactivation of C3 was found in vitro. Similarly, no free proteolytic activity could be detected in the patient's serum, and serum concentrations of known protease inhibitors were normal.Complement-mediated functions, which were markedly deficient in the patient's serum, could be restored partially or completely by the addition of a 5-6S heat-labile beta pseudoglobulin from normal serum. The C3 proinactivator, which has these physicochemical characteristics, was also shown to be either absent or nonfunctional in the patient's serum. An unidentified 6S beta pseudoglobulin to which a monospecific antiserum was available was not detectable in the patient's serum. This last protein appeared not to be a complement component, nor was it the C3 inactivator or proinactivator. Finally, the substance or substances necessary for the conversion of C3b to C3c were missing from the patient's serum. The administration of 500 ml of normal plasma to the patient corrected all of his abnormalities partially or completely for as long as 17 days. The changes in C3 were dramatic; serum concentration rose from 8 to 70 mg/100 ml, and C3b could no longer be detected. A second metabolic study during this normalization period showed a decrease in fractional catabolic rate toward normal. The patient's histamine excretion was constantly elevated but increased further after a warm shower and after receiving normal plasma; at both times he had urticaria. These observations were consistent with the endogenous production of C3a and the resulting histamine release from mast cells. The inactivating mechanism for C3a was apparently intact in the patient's serum. The difference in the electrophoretic mobilities of C3b and C3c was shown as well as the electrophoretic heterogeneity of C3c. Suggestive evidence was also presented that the form of C3 with an activated combining site for red cells, previously postulated by others, is a transient C3 conversion product with an electrophoretic mobility slower than that of C3 on agarose electrophoresis.

Adult↗

PubMed2001

Expression and regulation of complement factors H and I in rat and human cells: some critical notes.

The complement factors I (FI) and H (FH) are complement regulatory proteins. FI, a highly glycosylated serine protease of 88 kDa cleaves the alpha-chains of both complement components C3b and C4b, thereby inactivating them. Complement FH, a glycoprotein of 150 kDa which is composed of 20 short consensus repeats synergizes with FI by increasing the affinity of FI for C3b in the C3b/FH complex by about 15-fold as compared to free C3b. Furthermore, FH prevents factor B from binding to C3b and promotes the dissociation of the C3bBb complex. Both, FI and FH are mainly synthesized in the liver. According to the quantification of specific mRNA of both factors, various amounts are produced by different liver cell types, i.e. hepatocytes (HC) and Kupffer cells (KC). Investigations of cultured primary HC and KC from rat liver showed that FI is exclusively synthesized and secreted by HC whereas FH is synthesized by both HC and KC. Using quantitative-competitive PCR for the quantification of FH-specific mRNA, its constitutive rate of synthesis was found to be nearly ten times higher in KC than in HC. An extrahepatic source of both proteins are human umbilical vein endothelial cells (HUVEC) in which the synthesis of FI is upregulated by IL-6 which is in accord with the upregulation observed in rat HC and two rat hepatoma cell lines (FAO and H4IIE). Three other proinflammatory cytokines, IL-1beta, IFN-gamma and TNF-alpha, were alone or in combination, without any effect on the regulation of FI. This demonstrates that the regulation of FI is similar in HUVEC and HC. These results are in contrast to a previously described IFN-gamma-mediated upregulation of FI in HUVEC and suggest, in accordance with other investigations on extrahepatic sources of FI (e.g. myoblasts), that IFN-gamma has probably no prominent role in the regulation of FI. Instead, IL-6 appears to be the main upregulating cytokine of FI mRNA and of FI protein synthesis in HC as well as in rat and human hepatoma cells and in HUVEC. Of note are experiments by others and us who could not identify FI-specific mRNA in peripheral blood-derived monocytes, granulocytes, or B- and T-cells of man or rat and in rat peritoneal macrophages. FI-specific mRNA could also not be detected in B- or T-cell lymphoma cells, whereas FH-specific mRNA was easily detectable in both human and rat monocytes, and in rat peritoneal macrophages. These data support the notion that FI in contrast to FH is not expressed by cells of the monocyte-macrophage lineage or by other leukocytes of peripheral blood, at least in the absence of additional stimulants.

Animals↗

PubMed1983

Visualization of human C4b-binding protein and its complexes with vitamin K-dependent protein S and complement protein C4b.

C4b-binding protein (C4bp) participates in the regulation of the C3 convertase of the classical pathway of complement. By binding to C4b, which is one of the structural subunits of this enzyme, C4bp accelerates the decay-dissociation of the enzyme and renders C4b susceptible to degradation by factor I (C3b inactivator). C4bp is a high molecular weight plasma protein (Mr = 570,000) composed of apparently identical subunits (Mr = 70,000) linked by disulfide bonds. In plasma and in purified form C4bp also forms a bimolecular complex (Kd = 0.9 X 10(-7) M) with protein S, a recently identified vitamin K-dependent plasma protein. The binding sites on C4bp for protein S and C4b are distinct and noncompetitive and protein S does not influence the function of C4bp as a regulator of the C3 convertase. C4bp, C4b, and protein S were visualized by electron microscopy by negative staining. C4bp was found to have an unusual spider-like structure. It is composed of seven thin (30 A), elongated (330 A), and flexible subunits that are linked to a small central body. Protein S exhibited two globular domains of equal size with a center-to-center distance of approximately equal to 50 A. Protein S was found to bind to the C4bp through only one of its domains by attaching to a short subunit that is distinct from the other seven subunits. C4b imaged as an irregular, relatively compact molecule. It was found to interact with the peripheral ends of the elongated subunits, suggesting seven C4b-binding sites per molecule of C4bp.

Carrier Proteins↗

PubMed2006

Functional characterization of the complement control protein homolog of herpesvirus saimiri: ARG-118 is critical for factor I cofactor activities.

Herpesvirus saimiri (HVS) is a lymphotropic virus that causes T-cell lymphomas in New World primates. It encodes a structural homolog of complement control proteins named complement control protein homolog (CCPH). Previously, CCPH has been shown to inhibit C3d deposition on target cells exposed to complement. Here we have studied the mechanism by which it inactivates complement. We have expressed the soluble form of CCPH in Escherichia coli, purified to homogeneity and compared its activity to vaccinia virus complement control protein (VCP) and human complement regulators factor H and soluble complement receptor 1. The expressed soluble form of CCPH bound to C3b (KD = 19.2 microm) as well as to C4b (KD = 0.8 microm) and accelerated the decay of the classical/lectin as well as alternative pathway C3-convertases. In addition, it also served as factor I cofactor and supported factor I-mediated inactivation of both C3b and C4b. Time course analysis indicated that although its rate of inactivation of C4b is comparable with VCP, it is 14-fold more potent than VCP in inactivating C3b. Site-directed mutagenesis revealed that Arg-118, which corresponds to Lys-120 of variola virus complement regulator SPICE (a residue critical for its enhanced C3b cofactor activity), contributes significantly in enhancing this activity. Thus, our data indicate that HVS encodes a potent complement inhibitor that allows HVS to evade the host complement attack.

Arginine↗

PubMed1977

Pathways of complement activation in membranoproliferative glomerulonephritis and allograft rejection.

The complement system is comprised of at least 18 plasma proteins and consists of four functional divisions: two pathways for activation (classical and alternative), a common amplification mechanism for the activating pathways, and a final common effector pathway to which the activating and amplifying sequences are directed. The classical pathway is activated by certain antigen-antibody complexes, while the alternative pathway may be initiated non-immunologically by various microbial polysaccharides. Indeed, mixtures of purified C3, B, D, and P regulated to low-grade interaction by the presence of C3bINA and beta1 H respond to zymosan with amplified C3 and B inactivation. Both pathways form enzymes termed C3 convertases that cleave C3 to generate its major fragment, C3b. C3b interacts with each C3 convertase to permit C5 cleavage in activation of the effector complement sequence, and it interacts with alternative-pathway factors B and D to generate additional C3 convertase, C3bBb, in the amplification pathway. As C3 cleavage represents the most critical step in the elaboration of the biologic effects of the complement system, modulation of this reaction by generation, stabilization, and inactivation of the amplification convertase C3bBb may well determine whether initial activation of the complement sequence eventuates in beneficial or detrimental effects for the host. Initial generation of C3bBb is dependent on prior cleavage of C3, which may occur by the classical pathway or the alternative pathway. Stabilization of C3bBb is achieved with either P or C3NeF after their binding to C3b and C3bBb, respectively. Control of this amplifying step occurs at three levels: intrinsic decay of the inherently labile C3bBb complex, extrinsic decay-dissociation of Bb from the complex by beta1H, and inactivation of C3b by C3bINA. In the presence of stabilizing factors the control proteins must function in sequence, since C3bINA cannot act on C3bBb; beta1H-mediated decay of protective Bb must precede C3b inactivation by C3bINA. C3NeF, which is found in the sera of some patients with MPGN and persistent depressions of serum C3, circumvents all three controls because of its capacity to create a stabilized convertase that is relatively resistant to decay-dissociation by beta1H. The effector complement sequence is activated by cleavage of C3 and C5, which releases vasoactive and chemotactic peptides, C3a and C5a, and generates the major fragments C3b and C5b. C3b, in addition to its function in the amplifying reaction and the C5 convertases, mediates immune adherence to cells possessing membrane-associated receptors for C3b; this in turn promotes the phagocytic and secretory functions unique to each cell type. Cell-bound C5b serves to assemble the cytolytic complex C5b6789, while fluid-phase C5d generates the hemolytically inactive chemotactic complex C567d...

Complement C3↗

PubMed1974

Metabolic studies of the third component of complement and the glycine-rich beta glycoprotein in patients with hypocomplementemia.

Metabolic studies using radioiodine-labeled third component of complement (C3) and the glycine-rich beta glycoprotein (GBG), a major component of the C3b-feedback pathway, were undertaken in normal subjects, in 22 patients with evidence of complement activation, and in 11 patients with various renal diseases without evidence of complement activation. In seven normal subjects GBG was found to be a rapidly metabolized protein with catabolic rates ranging from 1.7% to 2.2% of the plasma pool/h, synthesis rates from 0.14 to 0.21 mg/kg per h. and extravascular/intravascular distribution ratios from 0.81 to 1.31. In patients with reduced plasma C3, both increased C3 fractional catabolic rates and reduced C3 synthesis rates were observed, and in some patients there was evidence of increased extravascular distribution of the protein. GBG catabolism was usually increased when there was evidence of C3 activation, presumably reflecting activation of the C3b-feedback; but GBG turnover was normal or only slightly accelerated in some patients with accelerated C3 catabolism and profound hypocomplementemia, suggesting that reduced C3 synthesis had limited activation of the C3b-feedback.

Complement Inactivator Proteins↗

PubMed1978

C3 component of complement secreted by established cell lines.

The hamster cell line NIL8 secretes the C3 component of complement as well as collagenous molecules and fibronectin (LETS protein). The C3 is found in the culture medium as a disulfidebonded complex of two polypeptides of 130,000 daltons (alpha) and 65,000 daltons (beta). The secreted C3 can be quantitatively cleaved to C3b and further cleaved by C3 inactivators. The activation of C3 to C3b is promoted by zymosan or by antibody-coated erythrocytes, demonstrating participation in both the classical and alternative complement pathways. The availability of this culture system has enabled us to show that C3 is synthesized as a 185,000 dalton precursor (proC3) which is biologically inactive and becomes cleaved to active C3. Some other established cell lines (NIL1 and BALB/c 3T3) also secrete C3, but some others do not.

Animals↗

PubMed1977

Decreased opsonization for Streptococcus pneumoniae in sickle cell disease: studies on selected complement components and immunoglobulins.

Opsonic activity for Streptococcus pneumoniae in the sera of patients with sickle cell disease was reduced in comparison to the opsonic activity of sera from age-matched normal children. No difference in opsonic activity for Escherichi coli was observed in the sera from patients or normals. Total hemolytic complement, conversion of C3 by inulin and cobra venom factor, and levels of C3, factor B, properdin, C3b inactivator, and immunoglobulins G, A, and M were normal in patients' sera. The opsonic abnormality for S. pneumoniae was attributed to a deficiency of serum proteins rather than to an inhibitor of opsonic function. The data suggest that decreased opsonization was not associated with a deficiency of those complement components or immunoglobulins measured in this study.

Adolescent↗

PubMed1975

Evidence for macrophage C3d-receptor active in phagocytosis.

Evidence is presented that guinea pig peritoneal macrophages possess membrane receptors able to recognize the C3b inactivator-cleaved third component of complement. This conclusion is based on the finding that rosette formation and phagocytosis by macrophages of EA-IgM-C1423 were equal regardless of whether EA-IgM-C1423 had been pretreated with C3b inactivator or not.

Animals↗

PubMed1978

Assembly of the cytolytic alternative pathway of complement from 11 isolated plasma proteins.

The known cytolytic function of the alternative pathway in serum was quantitatively reproduced by combining 11 isolated plasma proteins at their respective serum concentrations. These proteins are: C3, Factor B, Factor D, C3b inactivator, beta1H, native properdin, C5, C6, C7, C8, and C9. In absence of activators of the alternative pathway, this mixture was stable at 37 degrees C as evidenced by lack of consumption of Factor B, C3, and C5. Upon addition of either rabbit erythrocytes or neuraminidase-treated sheep erythrocytes, cell lysis ensued and the extent of lysis was dependent on dose of the component mixture. The dose-response curves obtained with the isolated component mixture and with C4-depleted serum were virtually indistinguishable. Nonactivator erythrocytes (untreated sheep erythrocytes) were not lysed by the component mixture. Deletion of properdin resulted only in a twofold diminution of the hemolytic activity of the component mixture. No immunoglobulin requirement was apparent. These results indicate that the cytolytic systems studied are internally sufficient and capable of coupling the initiation and amplification sequence with the cytolytic membrane attack sequence.

Cell-Free System↗

PubMed1999

Rat complement factor I: molecular cloning, sequencing and expression in tissues and isolated cells.

Factor I (FI) is a regulatory serine protease of the complement system which cleaves three peptide bonds in the alpha-chain of C3b and two bonds in the alpha-chain of C4b thereby inactivating these proteins. The human protein and the recently characterized mouse factor I are heterodimers of about 88,000 MW which consist of a non-catalytic heavy chain of 50,000 MW which is linked to a catalytic light chain of 38,000 MW by a disulphide bond. For the screening of a rat liver cDNA library we used a hybridization probe produced by polymerase chain reaction (PCR) using degenerated primers which corresponded to conserved parts of the human and the murine factor I nucleotide sequences. One of the identified sequences, which had a length of 2243 base pairs (bp), contained the complete coding region and the whole 3' untranslated region. The length of the coding region in rat consisted of 1812 bp followed by a 3' untranslated region of 207 bp including the polyadenylation signal and the beginning of the poly A tail. Comparison of the rat cDNA-derived coding sequence revealed identities of 87% to the mouse and of 78% to the human FI nucleotide sequence. The translation product of rat FI mRNA was 604 amino acid residues (aa) in length with an identity of 85% to the mouse (603 aa) and 69% to the human protein (583 aa). The comparison of the molecular mass predicted by the primary structure and derived from rat FI isolated from rat serum as detected in immunoblot analyses suggested a glycosylation of more than 20% of the total mass of the FI protein. Expression studies using reverse transcription (RT)-PCR assays indicated that FI-specific mRNA could neither be identified in B cells, nor in T cells, monocytes or granulocytes from rat and human peripheral blood nor in rat peritoneal macrophages. These data were in agreement with the results of RT-PCR obtained with several human lymphoma cell lines (Jurkat, MOLT-4, HUT102, Wil 2-NS, Ramos, Raji, U937) all of which were devoid of FI-specific mRNA. In accord with our data from two rat hepatoma cell lines (FAO and H4IIE) and one from man (HepG2) only isolated rat hepatocytes (HC) but neither Kupffer cells (KC), hepatic stellate cells (HSC; Ito cells) nor sinusoidal endothelial cells (SEC) expressed FI-specific mRNA. FI mRNA was also detected in human umbilical vein endothelial cells (HUVEC) and in the uterus and small intestine of the rat. Spleen and lymph nodes did not contain any detectable FI-specific mRNA.

Amino Acid Sequence↗

PubMed1998

Helicobacter pylori urease significantly reduces opsonization by human complement.

The role of Helicobacter pylori urease in opsonization by human complement was investigated. H. pylori wild type strain N6 and isogenic mutants lacking either the large urease subunit (UreB) or an accessory urease protein (UreG) were incubated with different sera. C3b bound to the bacteria was measured by specific staining and flow cytometry. As compared with opsonization of N6 and the UreG-lacking mutant, opsonization of the UreB-lacking mutant was significantly increased after incubation with sera from both H. pylori uninfected (P<.001) or infected (P<.05) persons. However, when sera from uninfected persons were used, effective opsonization of this mutant proved to be dependent mainly on the classical pathway of complement activation. Irrespective of the serum used, opsonization values were very low after selective inactivation of the classical or the alternative pathway. Reduced opsonization of the urease-expressing strains could, to some extent, result from degradation of bound C3b.

Bacterial Proteins↗

PubMed2003

Cloning and expression of the complement receptor glycoprotein C from Herpesvirus simiae (herpes B virus): protection from complement-mediated cell lysis.

Simian herpes B virus (SHBV) is the herpes simplex virus (HSV) homologue for the species MACACA: Unlike in its natural host, and unlike other animal herpesviruses, SHBV causes high mortality in accidentally infected humans. SHBV-infected cells, like those infected with HSV-1 and equine herpesvirus types 1 and 4, express complement C3 receptor activity. To study immunoregulatory functions involved in susceptibility/resistance against interspecies transmission, the SHBV glycoprotein C (gC(SHBV)) gene (encoding 467 aa) was isolated. Sequence analysis revealed amino acid identity with gC proteins from HSV-2 (46.9 %), HSV-1 (44.5 %) and pseudorabies virus (21.2 %). Highly conserved cysteine residues were also noted. Similar to gC(HSV-2), gC(SHBV) is less glycosylated than gC(HSV-1), resulting in a molecular mass of 65 kDa if expressed in replication-deficient vaccinia virus Ankara. Stable transfectants expressing full-length gC(SHBV) on the cell surface induced C3 receptor activity and were substantially protected from complement-mediated lysis; no protection was observed with control constructs. This suggests that expression of the gC homologues on infected cell surfaces might also contribute to the survival of infected cells in addition to decreased virion inactivation. Interestingly, soluble gC(SHBV) isolated from protein-free culture supernatants did not interfere with the binding of the alternative complement pathway activator properdin to C3b, which is similar to our findings with gC(HSV-2) and could be attributed to major differences in the amino-terminal portion of the protein with extended deletions in both gC(SHBV) and gC(HSV-2). Binding of recombinant gC(SHBV) to polysulphates was observed. This, together with the heparin-sensitivity of the gC(SHBV)-C3 interaction on the infected cell surface, suggests a role in adherence to heparan sulphate, similar to the gC proteins of other herpesviruses.

Amino Acid Sequence↗

PubMed1993

Role of the YadA protein in prevention of opsonization of Yersinia enterocolitica by C3b molecules.

When mixed with normal human serum, wild-type pathogenic Yersinia enterocolitica, previously incubated at 37 degrees C, fixed less C3b than its variant cured of the virulence plasmid pYV. Mutants unable to secrete the Yop proteins were still protected against C3b deposition. By contrast, mutants deficient in the production of outer membrane protein YadA fixed more C3b than their YadA+ parent. Gene yadA, cloned as a minimal polymerase chain reaction fragment and introduced in trans, complemented the mutations. Production of YadA by recombinant Escherichia coli LK111 also resulted in a reduction of the amount of C3b deposited on the bacterial surface. The reduction of C3b at the surface of Y. enterocolitica YadA+ compared with YadA- cells correlated with an increase of the amount of factor H fixed at the bacterial surface. The YadA monomer separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and transferred to a nitrocellulose membrane was able to bind factor H. We conclude that factor H bound to YadA reduces the C3b deposition on the bacterial surface, probably by a rapid inactivation of C3b.

Adhesins, Bacterial↗