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M Oppermann

Publications and source records attributed to M Oppermann.

69 records · Page 4Linked to original sources
PubMed1991

Formation of C5a during cardiopulmonary bypass: inhibition by precoating with heparin.

A novel enzyme immunoassay based on direct detection of C5a by a monoclonal antibody (C17/5) specific for a neoepitope exposed in C5a/C5adesArg was used to measure in vivo and in vitro C5a formation during cardiopulmonary bypass. In vivo, we observed a significant threefold to fourfold increase in patient plasma C5a/C5adesArg levels from baseline values (5.6; 1.6 to 12.9 ng/mL) (median and range) up to 42 hours postoperatively (17.5; 6.5 to 46.0 ng/mL) when two different uncoated cardiopulmonary bypass circuits were used. Coating of the extracorporeal circuit with end-point-attached heparin completely abolished C5a formation in vitro during circulation of blood through the circuit for 120 minutes. The C5a concentration (median and range) was 3.2 (2.6 to 15.9) ng/mL at the start and 3.1 (2.7 to 15.0) ng/mL at the end of the experiment. In the uncoated setups the corresponding C5a concentrations were 10.1 (6.2 to 17.5) and 19.7 (13.1 to 24.3) ng/mL. Finally, heparin-coated cardiopulmonary bypass circuits were examined in vivo. C5a levels did not increase significantly during the cardiopulmonary bypass period in the heparin-coated group in contrast to the uncoated group, but the postoperative increase in C5a levels was similar in the two groups. We conclude that heparin coating improves biocompatibility by completely abolishing C5a formation in vitro. The discrepancy between the in vitro and the in vivo findings is probably related to the complicated biological turnover of C5a.

Antibodies, Monoclonal↗
PubMed1991

Elevated plasma levels of the immunosuppressive complement fragment Ba in renal failure.

The complement fragment Ba is a 33 kD activation product of factor B which suppresses human B-lymphocyte functions in vitro. We report that plasma levels of Ba are highly elevated in patients with chronic renal failure (4.84 +/- 3.58 micrograms/ml) and in patients with end-stage renal disease undergoing regular hemodialysis (16.1 +/- 6.1 micrograms/ml) as compared to normals (1.01 +/- 0.30 micrograms/ml). Ba levels were strictly correlated with the creatinine clearance. The urinary excretion of Ba was 165-fold higher in patients with tubular proteinuria than in normals. These results indicate that the kidney is the major catabolic site for Ba. In addition, direct evidence was obtained for an enhanced turnover of the alternative pathway of complement in renal failure that, although it appears to be less important than the renal retention of Ba, contributes to elevated Ba plasma levels in these patients. Ba concentrations in dialysis patients who responded to hepatitis B vaccination were significantly lower than in non-responders. Furthermore, the in vitro IgM synthesis by purified mononuclear cells was negatively correlated with Ba concentrations determined in the plasma of these patients. These results suggest that the accumulation of Ba contributes to the defective immune response in patients with renal failure.

Adult↗
PubMed1991

Complement activation and depletion during LDL-apheresis by heparin-induced extracorporeal LDL-precipitation (HELP).

The heparin-induced extracorporeal elimination of low density lipoproteins (LDL) is a well-established clinical procedure to markedly reduce cholesterol levels. The biocompatibility of this artificial filter system (HELP) was investigated by quantitation of representative complement proteins within the extracorporeal circuit using established ELISA procedures, based on monoclonal antibodies recognizing exclusively either native (C6, C7) or activated proteins (act.C3, C5a, TCC). HELP was found to be a self-limiting extracorporeal system with respect to complement activation, since act.C3 and TCC, generated mainly at the plasma filter, were partially adsorbed to the following HELP specific filters to concentrations which were lower than those obtained before the plasma filter. C5a, which increased 14.5-fold at the plasma filter was not eliminated by the following filters; however, elevated levels were not found in the patients at the end of apheresis and no leucocytopenia was observed.

Adult↗
PubMed1991

A sensitive enzyme immunoassay for the quantitation of human C5a/C5a(desArg) anaphylatoxin using a monoclonal antibody with specificity for a neoepitope.

The direct quantitation of C5a/C5a(desArg) in human plasma was achieved by a specific and highly sensitive ELISA which is based on the neoepitope-specific monoclonal antibody C17/5. The error-prone removal of C5 from plasma prior to the assay is therefore not required. With a detection limit of 20 pg C5a/ml plasma, the sensitivity of this assay allowed to define normal ranges (1.94 +/- 1.49 ng C5a/nl, mean +/- SD) of C5a/C5a(desArg) in human blood plasma. This assay will also be applicable to the quantitation of C5a in specimens with low protein content where precipitation-based assays fail to accurately determine C5a. In addition, the mAb C17/5 turned out to efficiently block the binding of C5a/C5a (desArg) to its cellular receptor and therefore provides a valuable tool in the delineation of C5a effects in complex biologic systems in the presence of native C5, such as under in vivo conditions.

Adenosine Triphosphate↗
PubMed1991

Inhibition of terminal complement complex formation and cell lysis by monoclonal antibodies.

Three monoclonal antibodies (mabs), two against C5 and one against C6, were identified and characterized. They inhibited the generation of the terminal complement complex (TCC) in serum to over 90% as assayed by a sensitive ELISA based on a neoepitope-specific mab, which recognized TCC-integrated C9. The haemolytic function of the TCC was markedly reduced by all three mabs implying that they are directed to epitopes on C5 and C6 which are essential for TCC formation in both the fluid phase and on erythrocyte membranes. Since the generation of C5a was also impaired by these mabs, they may serve as tools in investigations of the sequelae of the generation of C5a and of TCC.

Antibodies, Monoclonal↗
PubMed1990

Quantitation of components of the alternative pathway of complement (APC) by enzyme-linked immunosorbent assays.

Sensitive enzyme-linked immunosorbent assays (ELISA) using monoclonal antibodies have been developed to specifically detect components of the alternative pathway of complement in human blood plasma. Normal values of the factor B split products Ba (1.01 +/- 0.30 micrograms/ml, mean +/- SD), Bb (0.65 +/- 0.23 micrograms/ml), of the C3-fragments C3b/iC3b/C3dg (17.9 +/- 5.7 micrograms/ml), native factor B (238 +/- 48 micrograms/ml), factor D (1.05 +/- 0.27 micrograms/ml), and factor H (702 +/- 292 micrograms/ml) were determined in the EDTA-plasma of healthy probands (n = 55). The simultaneous quantitation of the main cleavage products and of control proteins in the plasma samples permits precise analysis of the activation of the alternative pathway of complement in various disease states. In addition, we describe a method for the specific depletion of factor B prior to fragment-specific assays utilizing monoclonal antibodies conjugated to paramagnetic beads. The latter should permit the quantitation of other complement split products.

Animals↗
PubMed1990

Determination of the epitope specificities of monoclonal antibodies using unprocessed supernatants of hybridoma cultures.

A double monoclonal antibody (mAb) ELISA has been developed to determine the epitope specificities of murine monoclonal (mAbs). It permits the mAbs which bind to the same or adjacent epitopes to be distinguished from those which bind to separate epitopes on soluble monomeric proteins. The assay is designed for the early evaluation of mAbs in hybridoma culture supernatants when purified or labeled mAbs are not available. It does not rely on chemical or enzymatic fragmentation of the antigen and does not generate results which may be due to differences in the affinities of the mAbs. Moreover the characteristic multiple binding of polyclonal antibodies to the same epitope is also avoided. A further advantage is the accessibility of epitopes on a given antigen since the antigen is presented by a solid-phase mAb, in contrast to assays in which the antigen itself is adsorbed onto the solid phase. The test was evaluated using culture supernatants from hybridomas which produced mAbs against the complement proteins C3a, C6 or C7.

Animals↗
PubMed1989

Increase of glucose and lactate output and decrease of flow by human anaphylatoxin C3a but not C5a in perfused rat liver.

The complement fragments C3a and C5a were purified from zymosan-activated human serum by column chromatographic procedures after the bulk of the proteins had been removed by acidic polyethylene glycol precipitation. In the isolated in situ perfused rat liver C3a increased glucose and lactate output and reduced flow. Its effects were enhanced in the presence of the carboxypeptidase inhibitor DL-mercaptomethyl-3-guanidinoethylthio-propanoic acid (MERGETPA) and abolished by preincubation of the anaphylatoxin with carboxypeptidase B or with Fab fragments of an anti-C3a monoclonal antibody. The C3a effects were partially inhibited by the thromboxane antagonist BM13505. C5a had no effect. It is concluded that locally but not systemically produced C3a may play an important role in the regulation of local metabolism and hemodynamics during inflammatory processes in the liver.

Anaphylatoxins↗
PubMed1988

Complement activation in patients with renal failure as detected through the quantitation of fragments of the complement proteins C3, C5, and factor B.

Using sensitive and highly specific enzyme-linked immunosorbent assays fragments of the complement proteins C3, C5, and factor B were quantitated in patients with renal failure. During hemodialysis on new cuprophan membranes raised levels not only of C3a, but in addition of activated C3, C5a, and Ba were demonstrated. In patients with chronic renal failure and end-stage renal disease plasma concentrations of Ba and activated C3 were markedly elevated independent of hemodialysis. This finding is taken as an indication of a continuous recruitment of the alternative pathway of complement in these patients. As the detected complement protein fragments are known to exert immune regulatory functions these findings may imply that these peptides are involved in the maintenance of the immune suppressed state in renal failure.

Acute Kidney Injury↗
PubMed1981

[Antinuclear antibodies in diagnosis of rheumatic diseases (author's transl)].

Hundred ana-positive sera--60 sera of SLE-patients and 40 sera of patients suffering from rheumatoid arthritis--were investigated for ana and DNA-antibodies. For these purposes nine different methods including several radioimmunological and immunofluorescence techniques with partially distinct antigen-specificities were tested. While the radioimmunoassays showed only slightly different results, significant differences in sensitivity as well as in antibody specificity existed mainly in the indirect immunofluorescence techniques using different substrates. For clinical use, a combination of various techniques seemed to be useful i.e. indirect immunofluorescence on hemolysed bird erythrocytes and on frozen native rat liver sections. For DNA-antibodies in diagnosis and control during the course of the diseases the radioimmunoassay with simultaneous detection of antibodies to single- and double stranded DNA is most suitable. Antibodies to distinct nuclear antigens are detectable in various amount in the rheumatic diseases. While ds-DNA-antibodies seemed to be most specific for SLE, ss-DNA-antibodies occurred in nearly all ana-positive sera and seemed to be less specific for one disease than all the other ana-fractions.

Animals↗
PubMedDate not supplied

Assessment of complement activation in vivo.

Hemolytic assays that measure the functional integrity of the complement system and the quantitation of individual components by immunochemical techniques have been widely used in the past for the assessment of in vivo complement activation. However, the complement system comprises a large number of interacting serum proteins which are subject to independent synthetic and catabolic processes. The fact that complement proteins are rapidly metabolized under in vivo conditions adds to the complexity of complement analysis. Assays that are based on monoclonal antibodies with specificities for activation-dependent neoepitopes now allow the direct determination of complement fragments in plasma. These methods are superior to the quantitation of native proteins. Several parameters that differentially affect the generation or the catabolism of individual complement activation products still have to be taken into account when elevated plasma levels of complement fragments suggest in vivo complement activation. These factors include the binding to complement fragment receptors, the degradation by serum proteases and renal or hepatic clearance. An accurate estimation of complement activation in vivo requires the simultaneous determination of both the native components and the activation products.

Animals↗
PubMedDate not supplied

The contrasting mechanisms of serum resistance of Neisseria gonorrhoeae and group B Neisseria meningitidis.

Neisseria gonorrhoeae and Neisseria meningitidis have evolved intricate mechanisms to evade complement-mediated killing. Sialylation of gonococcal lipooligosaccharide (LOS) results in conversion of previously serum sensitive strains to unstable serum resistance, which is mediated by factor H binding. Porin (Por) is also instrumental in mediating stable serum resistance in gonococci. The 5th loop of certain gonococcal PorlAs binds factor H, which efficiently inactivates C3b to iC3b. Factor H glycan residues may be essential for factor H binding to certain Por1A strains. Por1A strains can also regulate the classical pathway by binding to C4b-binding protein (C4bp) probably via the 1st loop of the Por molecule. Certain serum resistant Por1 B strains can also regulate complement by binding C4bp through a loop other than loop 1. Purified C4b can inhibit binding of C4bp to Por 1B, but not Por1A, suggesting different binding sites on C4bp for the two Por types. Unlike serum resistant gonococci, resistant meningococci have abundant C3b on their surface, which is only partially processed to iC3b. The main mechanism of complement evasion by group B meningococci is inhibition of membrane attack complex (MAC) insertion by their polysaccharide capsule. LOS structure may act in concert with capsule to prevent MAC insertion. Meningococcal strains with Class 3 Por preferentially bind factor H, suggesting Class 3 Por acts as a receptor for factor H.

Blood Bactericidal Activity↗
PubMedDate not supplied

Significant reduction of factor D and immunosuppressive complement fragment Ba by hemofiltration.

Because of their effect on the immune response, especially in patients with chronic or acute renal failure, factor D (FD) and the immunosuppressive complement fragment Ba are substances which may be important for the immunological status. Since they cannot be eliminated by conventional Cuprophan hemodialysis because of their high molecular weight (24,000 and 33,000 D, respectively), the effect of hemofiltration (HF) on the plasma concentration of both components was tested. It was shown that plasma levels of FD can be lowered by 43.5% during an HF treatment and the plasma concentration of Ba by 30.6%. Moreover, the two substances could be detected in the hemofiltrate. Up to 75 mg FD and up to 37 mg Ba could be eliminated per treatment, depending on the plasma concentrations and the filtration volume. A convective method such as chronic HF is therefore clearly superior to diffusive methods of blood purification when substances with such a high molecular weight have to be eliminated. It has still to be established whether the elimination of FD and Ba by chronic intermittent HF results in a sustained improvement in the immunological status of patients treated in this way.

Adult↗
PubMedDate not supplied

[Panhypogammaglobulinemia: a rare complication of parenteral gold therapy].

Secondary antibody deficiency is one of the rare adverse effects of chrysotherapy in rheumatoid arthritis. The plasma levels of all immunoglobulins fall into ranges significantly lower than the tolerable physiological minimum. The long-lasting panhypogammaglobulinemia can increase the risk of infection in the patient and, therefore, should be closely monitored. Hence, a record of immunoglobulin levels before and during therapy with gold compounds seems to be mandatory.

Agammaglobulinemia↗