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Evolution of alpha 2-macroglobulin. The structure of a protein homologous with human alpha 2-macroglobulin from plaice (Pleuronectes platessa L.) plasma.

The plaice (Pleuronectes platessa L.) papain-binding protein previously demonstrated to be homologous with human alpha(2)-macroglobulin, and designated plaice alpha(2)-macroglobulin homologue or alphaMh, was shown to be a glycoprotein of s(20,w) 11.86S. In polyacrylamide-gel pore-limit electrophoresis under non-denaturing conditions plaice alphaMh migrated to the same position as half-molecules of human alpha(2)-macroglobulin, and treatment with methylamine or a proteinase caused no change in its electrophoretic properties. Either denaturation in urea (4m) or mild reduction by dithiothreitol (1mm) partially dissociated plaice alphaMh into half-molecules. Denaturation with reduction further dissociated the protein into quarter-subunits. In sodium dodecyl sulphate/polyacrylamide-gel electrophoresis under reducing conditions plaice alphaMh dissociated into subunits of M(r) 105000 (I) and 90000 (II). Approximately equal amounts of each subunit were formed, and peptide ;mapping' showed subunits I and II to be distinct polypeptide chains. Under alkaline denaturing conditions, a proportion of the I chains of alphaMh were cleaved into fragments of M(r) about 60000 and 40000. This cleavage was favoured by reducing conditions and prevented by prior inactivation of the alphaMh with methylamine. [(14)C]Methylamine allowed to react with alphaMh became covalently linked to subunit I. These properties suggested the existence of an autolytic site on subunit I analogous to the autolytic site of human alpha(2)-macroglobulin. Reaction of alphaMh with a proteinase resulted in cleavage of a fragment of M(r) 10000-15000 from subunit I. A proportion of the proteinase molecules trapped by alphaMh became covalently linked to the inhibitor. A scheme is proposed for the evolution of human alpha(2)-macroglobulin and plaice alphaMh from a common ancestral protein, which may also have been an ancestor of complement components C3 and C4.

Amino Acid Sequence↗

[Complex evaluation of the defense systems in patients with infiltrative pulmonary tuberculosis].

Patients with infiltrative pulmonary tuberculosis at its degenerative stage were examined for parameters of hemostasis, serum proteolytic inhibitors, immunity status and complement. In doing so, the following changes were detected: simultaneous intensification of plasma coagulability and fibrinolytic properties, sputum-induced increase in fibrinolysis; disproportion in the content of the main protease blockers (higher alpha 1-protease inhibitor and lower alpha 2-macroglobulin); T-lymphocyte deficiency; stimulation of the immunity humoral link; rise in the count of O-lymphocytes and higher concentration of the complement component C3. The correlation between the indices of the examined systems was observed, thus indicating the interdependence of the body defensive factors. The findings can be used in the clinical practice when pathogenetic drugs are chosen.

B-Lymphocytes↗

Lymphocytes stimulated by allogeneic B cell lines cleave the third component of complement and fix C3 fragments. Their nonspecific lytic capacity is elevated against complement receptor type 2-carrying targets.

Human blood lymphocytes stimulated in mixed cultures by allogeneic B cell lines were shown to cleave C3 molecules. The B cell lines were derived from Burkitt lymphoma patients: 1) established from their EBV-negative lymphoma, 2) the EBV-positive sublines converted in vitro, and 3) lymphoblastoid cell lines (LCL) i.e., B lymphocytes transformed in vitro by EBV. These cell lines differed considerably in their capacity to stimulate allogeneic lymphocytes. The split products of C3 were detected in the supernatants and on the surface of the activated lymphocytes at levels which correlated with the strength of stimulation. Lymphocytes cultured with LCL had the highest levels of thymidine incorporation blast transformation, C3 cleavage, and C3 fragment fixation. Lymphocytes exposed to the EBV-negative Burkitt lymphomas were stimulated weakly and their C3-activating capacity was low. Irrespective of the efficiency of lymphocyte stimulation induced in the cultures, 60 to 70% of the blasts were found to fix C3 fragments. The majority of the lymphocytes which fixed C3 fragments were T blasts that carried the CD3 marker and expressed IL-2R (CD25). CD4 and CD8 cells were represented with equal frequency in the C3-fragment fixing and C3-fragment negative populations. Pre-exposure of the MLC-activated lymphocytes to human serum increased their cytotoxic capacity toward CR type 2-carrying targets. The enhanced lysis was abrogated by F(ab)2 rabbit anti-human C3d or rabbit anti-CR type 2 antibodies. The results suggest that the C3 fragments fixed on the lymphocytes bind to CR on the targets and elevate the avidity of binding between the two interacting cells. This was also indicated by an increase in the frequency of lymphocyte-target conjugates.

Antigens, Differentiation, B-Lymphocyte↗

Acquired C1-esterase inhibitor deficiency and recurrent herpes infection in a patient with chronic lymphocytic leukemia.

Profound hypocomplementemia was observed in a patient with chronic lymphocytic leukemia. On the basis of the results of complement measurements performed in nine serum samples taken in a period of 6 mo it was demonstrated that the patient had an acquired form of C1-esterase inhibitor deficiency: marked reduction of CH50, C1, C4, and C1-esterase inhibitor levels with normal alternative pathway, C3, and factor B activities were found. The patient had no typical attacks of angioneurotic edema; however, angioedema-like facial swelling was observed on several occasions in connection with recurrent severe herpes simplex eruptions. The possible association of the marked and long-lasting hypocomplementemia with the clinical course of the herpes infection is discussed.

Angioedema↗

A requirement for membrane-associated phospholipase A2 in platelet cytotoxicity activated by receptors for immunoglobulin G and complement.

Platelets are potent antibody- and complement-dependent cytotoxic effector cells. We showed previously that a single platelet can lyse a target cell sensitized with immunoglobulin G (IgG) and complement components up to C3 (C integral of 3b denotes the target cell-bound fragment of complement up to C3; the precise nature of the bound C3 fragment has not been established), and that the complete cytotoxic system capable of specific recognition and lysis resides in platelet membranes. To define the components of platelet membranes required for cytotoxicity, a set of inhibitors of phospholipase A2 (PLA2) that act by different chemical mechanisms was tested. The lytic reaction is blocked at appropriate concentrations of bromophenacylbromide, mepacrine, and manoalide. When platelets are treated with bromophenacylbromide, inhibition of cytolytic activity and that of PLA2 enzymatic activity occur in parallel. Platelets release arachidonate when incubated with target cells bearing IgG and C integral of 3b, confirming that Fc gamma R and complement receptor trigger both PLA2 action and efficient lysis. Inhibition by thimerosal of a reverse reaction, i.e., reacylation catalyzed by acyltransferase, causes increased target cell lysis, presumably by increasing the products of PLA2 action. Platelet cytotoxicity is increased when platelets are pretreated with some products of PLA2: exogenous lysophospholipids and not free arachidonic acid increase cytotoxicity. Electron microscopy suggests that platelets and target cells may fuse, possibly as a result of the formation of lysophospholipids which are well-known membrane fusogens. Fixation with paraformaldehyde does not affect platelet cytotoxicity, suggesting that the complete cytotoxic system resides as a preformed complex in platelet membranes. The results indicate that platelet membrane-associated PLA2, together with receptors for Fc and complement, are required for platelet cytotoxicity.

Animals↗

Hypodermin A, a new inhibitor of human complement for the prevention of xenogeneic hyperacute rejection.

BACKGROUND: Hyperacute rejection (HAR) of discordant xenografts in the pig-to-human combination can be prevented using tranplants expressing transgenic molecules that inhibit human complement. Hypodermin A (HA), a serine esterase that degrades C3, was tested in the guinea-pig-to-rat and in the pig-to-human combinations. METHODS: Hypodermin A was tested in vitro, ex vivo, and in vivo models of HAR in the guinea-pig-to-rat combination. Hamster ovary cells (CHO) and a line of porcine aortic endothelial cells (PAEC11) were transfected with HA complementary DNA (cDNA). RESULTS: The pattern of degradation of rat and human C3 by HA was different (multiple bands lower than 40 kDa) from the physiologic pattern observed after spontaneous degradation of rat C3 or physiologic activation of human C3. The CH50 activity in serum was significantly lower in rats treated with 3.2 mg HA/kg than in untreated rats (45 +/- 16 U/ml vs. 700 +/- 63 U/ml, P < 0.05). Sera from rats injected with 3.2 mg/kg of HA were less effective in lysing guinea-pig endothelial cells (12 +/- 7%) than normal rat sera (79 +/- 3%; P < 0.001). Ex vivo, guinea-pig hearts perfused by rat serum supplemented with HA survived longer than those perfused by non-treated serum (210 +/- 34 and 154 +/- 71 min, respectively; P < 0.05). In vivo, guinea-pig hearts transplanted into HA treated rats survived longer than in non-treated rats (27 +/- 5 min vs. 13 +/- 4 min; P < 0.001). In the presence of human serum, smaller amounts of C6 and C5b-9 were deposited onto HA-transfected CHO cells than onto control cells. The mHA-PAEC11 cells were significantly more resistant to lysis by human C than control PAEC11 cells. CONCLUSIONS: These data suggest that transgenic HA could be used to prevent hyperacute xenogeneic rejection.

Acute Disease↗

Degradation of humoral host defense by Candida albicans proteinase.

The effect of an extracellular proteinase from the pathogenic yeast Candida albicans on the bactericidal and opsonizing activities of human serum was studied. The ability of human polymorphonuclear leukocytes to kill Staphylococcus aureus was greatly reduced when the bacteria were opsonized with human serum treated with the proteinase. The reduction in the opsonizing activity of human serum was attributed to degradation of the Fc portion of immunoglobulin G by the action of C. albicans proteinase as determined by immunoprecipitation reaction. However, the Fab portion of immunoglobulin G was resistant to proteolysis by the proteinase. A clear reduction in the bactericidal activity of human serum against Escherichia coli was observed when the serum was treated with C. albicans proteinase. The reduction of serum bactericidal activity was attributed to the degradation of complement C3 by proteolysis by the proteinase as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, while C5 resisted the action of the proteinase. As determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the proteinase also degrades endogenous proteinase inhibitors, such as alpha 2 macroglobulin and alpha 1 proteinase inhibitor, which are involved in regulating inflammation. These results suggest that destruction of a host's defense-oriented or regulatory proteins facilitates debilitation of the infected host.

Aspartic Acid Endopeptidases↗

Differential substrate and inhibitor profiles for human MASP-1 and MASP-2.

The mannan-binding lectin (MBL)-associated serine proteases (MASPs) circulate in serum complexed with mannan-binding lectin, a recognition molecule of the complement system. MASP-2 cleaves the complement components C4 and C2 to form the C3 convertase C4b2a. A definitive natural substrate for MASP-1 has not yet been described. We investigated the substrate specifities of MASP-1 and MASP-2 using cleavage of fluorescent amide substrates by recombinant and serum-derived MASPs. Recombinant MASP-1 cleaved Phe-Gly-Arg-aminomethylcoumarin (AMC) most rapidly at a rate of 16.8 nmol min(-1) microg(-1) rMASP-1. Recombinant MASP-2 barely cleaved any of 14 substrates used. This provides means of measuring MASP-1 activity in the absence of a known natural substrate. An assay for MBL-bound MASP-1 was established using the substrate Val-Pro-Arg-AMC. Assay of MBL-bound MASP-2 was done by cleavage of a natural protein substrate, C4. The condition of the serum used for the assays is important; simulated aging showed decreased detectable MASP-1 and MASP-2 activity. The inhibitors Z-D-Phe-Pro-methoxy-propylboroglycinepinanediol ester (boroMpg), anti-thrombin III in the presence and absence of heparin, hirudin and C1 inhibitor were tested against the MASPs. C1 inhibitor inhibits both enzymes, but the protease-serpin complex is unusually unstable at alkaline pH. The thrombin inhibitor boroMpg inhibited MASP-1 but not MASP-2 while hirudin did not inhibit either protease. Anti-thrombin III alone was not inhibitory, but in the presence of heparin inhibited both MASP-1 and MASP-2. The ancient origin of MASP-1 and its thrombin-like activity suggests its involvement in a coagulation-based defense mechanism in the early evolution of innate immunity.

Enzyme Inhibitors↗

Low levels of functional of alpha 1-proteinase inhibitor in the promotion of C3-cleavage by granulocyte-neutral proteases in pleural empyema.

It has been suggested that C3 breakdown by granulocyte-neutral proteases in pleural empyemas may be related to a decreased inhibitor potential for these enzymes. In the present study it was shown that in 17 infected pleural effusions, high proteolytic activity on 125I-labeled C3 (16.3% +/- 4.4%) correlated with low functional levels of alpha 1-proteinase inhibitor (alpha 1-PI), as determined by trypsin-inhibitory capacity (56.2 +/- 20.1 IU/ml; rs = -0.97, P less than .001), whereas in 18 sterile pleural effusions there was no such correlation (125I-labeled C3 cleavage, 2.2% +/- .2%; trypsin-inhibitory capacity, 192.6 +/- 26.7 IU/ml). However, alpha 1-PI and alpha 2-macroglobulin protein concentrations in infected and sterile effusions (as measured by immunodiffusion) were similar. Fifteen strains of three bacterial species--Streptococcus pneumoniae, Pseudomonas aeruginosa, and Proteus mirabilis--isolated from patients with pneumonia or empyema inactivated the elastase-inhibitory capacity of alpha 1-PI in vitro. These results show that in empyemas functional levels of alpha 1-PI were too low to inactivate granulocyte elastase and that some bacterial species may contribute to the low inhibitor potential of infected pleural fluid by direct alpha 1-PI inactivation.

Blood Proteins↗

Factors promoting colony stimulating activity (CSA) production in macrophages and epithelial cells.

The regulation of colony stimulating activity (CSA) release from CSA producing cells is a poorly understood process. Using freshly isolated mouse peritoneal cells and a continuous line of mouse thymic epithelial cells a precise and reproducible method of short term culture was developed to study this phenomenon. Serum, endotoxin, lithium, and cyclic GMP stimulated CSA release from both cell types. Particles such as zymosan, inulin, latex, and iron filings stimulated CSA release from mouse peritoneal cells but not from thymic epthelial cells. Theophylline and cyclic AMP inhibited CSA release from both cell types. Trypsin activated guinea pig C3 and C5 did not stimulate CSA release. Cycloheximide, an inhibitor of protein synthesis, completely inhibited CSA release. We believe these findings may reflect mechanisms of in vivo regulation of CSA release.

Animals↗

Acquired angioedema with lymphoproliferative disorder: association of C1 inhibitor deficiency with cellular abnormality.

A patient with a lymphoproliferative disorder, angioedema, and an acquired deficiency of the inhibitor of the activated first component of complement was studied. The patient's complement profile revealed depletion of the first component of complement, which has not been seen in angioedema of the hereditary type. There was no evidence for C1-depleting activity in the patient's plasma. The majority of the patient's peripheral blood mononuclear cells resembled B cells in their memebrane receptor properties and in that they carried easily detectable immunoglobulin, predominantly IgM. However, these cells were unusual in that they phagocytosed both latex particles and C3-coated erythrocytes. Morphological study of the cells infiltrating the patient's lung revealed immature, atypical, and plasmacytoid lymphocytes and immunoblasts. Both the patient's peripheral blood mononuclear cells and a suspension of cells from the pulmonary infiltrate were capable of depleting the first component of complement and its inhibitor from homologous plasma. Normal ABO-compatible cells did not possess this property. The data suggested that the patient's abnormal lymphoid cells may have interacted with the complement system to produce a biochemical defect and a clinical syndrome closely resembling angioedema of the hereditary type.

Aged↗

Characterization of the acute phase serum protein response in pigs.

Acute inflammation was induced in pigs using a single subcutaneous turpentine injection. The acute phase serum protein response was analyzed using crossed immunoelectrophoresis and immunodiffusion. The concentration of C reactive protein and haptoglobin increases 5-7 times 48 h after the injection, whereas the concentration of an alpha 2-globulin, named pig major acute phase protein (pig-MAP), increases at least 15-fold. A molecular mass of 115 kDa for pig-MAP was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This protein did not crossreact with antisera to human hemopexin, ceruloplasmin, H-kininogen and complement factor C3. Albumin and alpha-lipoprotein were negative acute phase proteins because their concentration significantly decreased during inflammation. Finally, the concentration of alpha 1-acid glycoprotein, fetuin, alpha 1-protease inhibitor, transferrin and alpha 2-macroglobulins, as well as total proteins, did not change significantly during inflammation.

Acute-Phase Proteins↗

Manufacture and in vitro characterization of a solvent/detergent-treated human plasma.

We have developed a modified solvent/detergent (S/D) treatment to inactivate viruses in human plasma using 1% w/w final concentration of tri(n-butyl) phosphate (TNBP) and Triton X-100 and an incubation period of 4 h at 30 degrees C. The procedure inactivates > or = 10(6) chimpanzee-infectious doses (CID50) of HBV, > or = 10(5) CID50 of HCV, and > or = 10(6.2) tissue culture infectious doses (TCID50) of HIV. After virus inactivation, eleven plasma batches were lyophilized and 12 batches were deep-frozen until further use. The batches were characterized by extensive laboratory tests including measurement of clotting factors I-XIII, von Willebrand factor, plasminogen, inhibitors of blood coagulation and fibrinolysis, and other clinically important plasma proteins. All parameters were determined before and after S/D treatment. Twelve conventional single donor plasma units served as control. There were no marked losses of activities of clotting factors, antithrombin III, protein C, plasminogen, and C1-esterase inhibitor due to treatment. After the S/D step, the levels of these parameters were within the normal range in all batches. The same holds true for total protein, immunoglobulins, albumin, complement factors C3 and C4, haptoglobin, hemopexin, caeruloplasmin, alpha 1-antitrypsin, and pH. Protein S and alpha 2-antiplasmin activities decreased by about 50% and were frequently found to be slightly below the lower limit of the respective normal range after treatment. The interindividual variations of all proteins analysed were significantly lower than in the single donor plasma units. The S/D procedure did not lead to increases of markers indicating activation of hemostasis.(ABSTRACT TRUNCATED AT 250 WORDS)

Antiviral Agents↗

Critical protection from renal ischemia reperfusion injury by CD55 and CD59.

Renal ischemia-reperfusion injury (IRI) is a feature of ischemic acute renal failure and it impacts both short- and long-term graft survival after kidney transplantation. Complement activation has been implicated in renal IRI, but its mechanism of action is uncertain and the determinants of complement activation during IRI remain poorly understood. We engineered mice deficient in two membrane complement regulatory proteins, CD55 and CD59, and used them to investigate the role of these endogenous complement inhibitors in renal IRI. CD55-deficient (CD55(-/-)), but not CD59-deficient (CD59(-/-)), mice exhibited increased renal IRI as indicated by significantly elevated blood urea nitrogen levels, histological scores, and neutrophil infiltration. Remarkably, although CD59 deficiency alone was inconsequential, CD55/CD59 double deficiency greatly exacerbated IRI. Severe IRI in CD55(-/-)CD59(-/-) mice was accompanied by endothelial deposition of C3 and the membrane attack complex (MAC) and medullary capillary thrombosis. Complement depletion in CD55(-/-)CD59(-/-) mice with cobra venom factor prevented these effects. Thus, CD55 and CD59 act synergistically to inhibit complement-mediated renal IRI, and abrogation of their function leads to MAC-induced microvascular injury and dysfunction that may exacerbate the initial ischemic assault. Our findings suggest a rationale for anti-complement therapies aimed at preventing microvascular injury during ischemia reperfusion, and the CD55(-/-)CD59(-/-) mouse provides a useful animal model in this regard.

Animals↗

The classical and alternative pathways of complement activation play distinct roles in spontaneous C3 fragment deposition and membrane attack complex (MAC) formation on human B lymphocytes.

The contributions of the classical (CP) and alternative (AP) pathways of complement activation to the spontaneous deposition of C3 fragments and the formation of membrane attack complexes (MAC) on human B lymphocytes, were assessed by incubating peripheral blood mononuclear cells with autologous serum in the absence and presence of selective inhibitors of the AP and CP, respectively. While the total amount of C3 fragments deposited was relatively unaffected by blocking either pathway individually, deposition was virtually abrogated by their combined blockade. A marked difference was observed, however, in the nature of the fragments deposited as a result of CP and AP activation: C3b fragments deposited via the CP were extensively ( approximately 90%) converted to the terminal degradation product, C3dg, whereas about 50% of those deposited by the AP persisted as C3b/iC3b fragments. The extent of MAC formation was also found to be highly pathway dependent, with the AP being about 15-fold more efficient at initiating this process than the CP. A model accounting for the effectiveness of the AP in both preserving C3 fragment integrity and initiating MAC is presented.

Acetylglucosamine↗

X-ray scattering study of hagfish protease inhibitor, a protein structurally related to complement and alpha 2-macroglobulin.

A protease inhibitor from hagfish blood plasma, homologous to human alpha 2-macroglobulin, has been studied in solution using small-angle X-ray scattering; the radius of gyration, R, was found to be 7.0 nm, the molecular weight 340,000 +/- 20,000, and the largest distance within the molecule, Dmax, 22 nm. When the inhibitor reacts with chymotrypsin, its 1:1 chymotrypsin complex is found to be more compact than the native molecule, R = 6.1 nm. A very similar conformational change is observed after the protein is reacted with methylamine. The data are consistent with models consisting of two equal elliptic cylinders with the same size as the one used as a model for the complement proteins C3 and C4 [cf. Osterberg et al. (1989) Eur. J. Biochem. 183, 507-511]. In the model for the native protein, these cylinders are arranged in an extended form, and in the one for the methylamine derivative (or chymotrypsin complex), they are closer together so that the projection of their elliptic surfaces forms an angle of about 70 degrees. These models for the hagfish protease inhibitor were expanded to models for the twice as large human alpha 2-macroglobulin using symmetry operations, and the resulting alpha 2-macroglobulin models were found to agree with those emerged from earlier studies involving electron microscopy and X-ray scattering methods.

Animals↗

Regulation of early complement components C3 and C4 in the synovium.

To determine the cytokine inducibility of early complement component (C3 and C4) expression in the synovium, explant tissue was maintained in culture for 7 days. C3 and C4 production was measured by specific enzyme-linked immunosorbent assay, and RNA was evaluated by semiquantitative PCR. The effects of leukemia inhibitory factor (LIF), gamma interferon (IFN-gamma), IFN-alpha, and estrogen on C3 and C4 expression were evaluated. C3 levels were unaffected by 7 days of LIF, IFN-gamma, or IFN-alpha treatment. In contrast, C4 levels were significantly induced in synovial samples treated for 7 days with either IFN-gamma or IFN-alpha. LIF had no effect on C4 levels in this system. Estrogen was found to down-modulate the induction of expression due to IFN-gamma. These data provide evidence for cytokine regulation of C4 expression in the synovium and for estrogen modulation of those effects.

Base Sequence↗

Hereditary angioneurotic oedema in Finland. Clinical, immunological and genealogical studies.

A total of 7 families with hereditary angioneurotic oedema (HANE) have been found in Finland. Six HANE patients have died from laryngeal oedema, 27 patients with diagnosed HANE are alive and 21 members have a haematological abnormality typical of HANE, i.e. a deficiency of the inhibitor of the activated first component of complement (C1-INH), but no manifest symptoms. The largest family has 363 living members, 303 of whom were investigated for C1-INH, C4 and C3. Fourteen patients had HANE, 18 relatives were symptomless but had C1-INH deficiency, and 3 members of the family had died from laryngeal oedema. In two families only one case of HANE was diagnosed, the parents in both cases being symptomless with normal C1-INH levels. All patients who had died from laryngeal oedema and 10 of the 27 HANE patients still alive had a typical triad of paroxysmal abdominal pain, peripheral oedema and laryngeal oedema. Six patients have had abdominal attacks alone, three peripheral oedema alone and two only laryngeal oedema. The age at onset of symptoms was 1-51 years. Three patients, who have received continuous methyltestosterone therapy, had hardly any symptoms during the treatment. Thirteen patients have received tranexamic acid, either during an attack or continuously, with positive effects in all except two. Cinnarizine treatment was beneficial in three out of four cases, both when given continuously or during an attack.

Abdomen↗