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PubMed1989

Altered concentrations of terminal complement complexes, anaphylatoxins, and leukotrienes in the coronary sinus during cardiopulmonary bypass.

The aim of this study was to determine if the hypoperfused heart activates complement with formation of anaphylatoxins, terminal complement complexes (TCC), or leukotrienes during cardiopulmonary bypass. Fifteen patients undergoing elective cardiopulmonary bypass surgery were studied regarding complement and leukotriene activation. Blood samples were drawn serially from the radial artery and coronary sinus. The plasma concentrations of the complement components C1INH, C3, C4, and C5 decreased during the procedure, whereas C3a and TCC increased. Protamine reversal of heparin further increased the plasma levels of C3a and TCC. No significant changes in plasma levels of C5a and leukotriene C4 were observed during cardiopulmonary bypass. The activity of the anaphylatoxin inactivator (AI) decreased in both the radial artery and the coronary sinus. There were no significant differences between the concentrations of complement components and leukotriene C4 in blood from the radial artery and coronary sinus. The levels of C3a and TCC increased and C1INH, C3, C4, C5, and the anaphylatoxin inactivator activity decreased to the same extent in the coronary sinus and the radial artery. Thus, the heart does not appear to be the primary site for the altered concentrations of these endogenous vasoactive substances.

Aged↗
PubMed2006

Bacterial complement evasion.

The human complement system is elemental to recognize bacteria, opsonize them for handling by phagocytes, or kill them by direct lysis. However, successful bacterial pathogens have in turn evolved ingenious strategies to overcome this part of the immune system. In this review we discuss the different stages of complement activation sequentially and illustrate the immune evasion strategies that various bacteria have developed to evade each subsequent step. The focus is on bacterial proteins, either surface-bound or excreted, that block complement activation. The underlying molecular mechanism of action and the possible role in pathophysiology of bacterial infections are discussed.

Animals↗
PubMed1987

Hereditary angioedema: a decade of management with stanozolol.

Thirty-seven patients with hereditary angioedema, who, without therapy, had attacks of cutaneous angioedema, gastrointestinal colic, and/or upper respiratory symptoms at a frequency and severity sufficient to prompt treatment with an attenuated androgen, have been evaluated for the incidence of side effects and biochemical toxicity during various schedules leading to the minimal effective dose. Stanozolol was administered in a 2 mg daily dose, initially, and after the symptoms and signs were adequately controlled for 2 months at this dose or at 1 mg per day, the drug was administered every other day at 4 mg. Patients who responded adequately to this schedule were administered 2 or 1 mg every other day, and then the interval between doses was gradually increased to 1 week, after which the agent was stopped. Eighteen patients experienced adverse reactions to stanozolol while the minimal effective dose was attained. In each instance the side effect subsided with a reduction in dosage. The most common adverse reactions were biochemical evidence of hepatic dysfunction and, to a lesser extent, hirsutism and menstrual irregularities. Although 21 of 27 patients in an initial study of the minimal effective dose were maintained with daily therapy in 1980, by 1986 this group and 10 additional patients were distributed so that three patients were receiving daily maintenance, 18 were receiving alternate-day maintenance, and 16 patients were receiving no maintenance therapy [corrected]. Thus, stanozolol appears to be a safe and effective agent for management of hereditary angioedema when patients are continually monitored to define the minimal effective dose or the feasibility of stopping the drug.

Adolescent↗
PubMed1997

Defensins purified from human granulocytes bind C1q and activate the classical complement pathway like the transmembrane glycoprotein gp41 of HIV-1.

The transmembrane glycoprotein gp41 of HIV-1 contains a C1q binding domain (HIVenv 583-610) and activates the human complement system through the classical pathway. Based on structural and functional similarities between human defensins (human neutrophil peptide, HNP 1-3) and synthetic peptides representing the env 583-610 region of HIV-1, we found it interesting to investigate the C1q binding and complement activating ability of human defensins. Human defensins were purified and characterized by size exclusion chromatography, ultrafiltration, gel electrophoresis and HPLC. The complement activating ability of the purified peptides was assessed in a solid-phase immunoassay. Defensins, fixed to an ELISA plate, were able to bind the C1q subcomponent of the first complement component (C1), triggering the classical pathway of complement activation which led to C4b binding to the plate. Reduction and subsequent alkylation of disulfide bridges of defensins greatly decreased the C1q binding ability but complement activation (C4b binding) remained high. Further acetylation of the reduced defensin peptide resulted in a molecule which bound very little or no C1q but still activated the complement cascade. These phenomena indicate that defensins interact with the complement system via C1q-dependent and C1q-independent mechanisms, and extend the number of functional similarities between defensins and gp41 of HIV-1 to include C1q binding and complement activation.

Anti-Infective Agents↗
PubMedDate not supplied

Complement activation following oxidative stress.

It is clear that complement plays an important role in the inflammatory process following oxidative stress in cellular and animal models. Clinical trials underway with novel complement inhibitors will establish the potential therapeutic benefit of complement inhibition in human disease. For as much as we understand about the role of complement in disease states, many questions remain. How is complement activated on endothelial cells following oxidative stress? What is the ligand for MBL on endothelial cells following oxidative stress? Will inhibition of MBL provide tissue protection to the extent observed with other complement inhibitors such as sCR1 or anti-C5 mAbs? These questions and more will undoubtedly be answered in the next millennium.

Animals↗
PubMed1988

The second component of human complement: detection of two hemolytic forms in plasma by pH variation.

The second component of human complement (C2) in pseudoglobulin prepared from normal plasma eluted as a single peak at high conductivity (30 mS) and pH 4.5 from the cationic exchangers S-Sepharose or Mono S in the Fast Protein Liquid Chromatography (FPLC) System. The C2 was stable at pH 4.5 and 0 degrees C if enzyme inhibitors were used and the pH was raised to 6.0 after elution from the columns. After rechromatography on Mono S in the FPLC System at the median isoelectric point of 5.5 or pH 6.0, the C2 eluted as two distinct hemolytic forms: the first peaked at 16 mS, the second at 30 mS. The two forms of C2 did not correlate with the allotypic variant of C2 in individual, normal human plasmas. After elution at pH 4.5 from S-Sepharose and rechromatography at pH 5.5 or 6.0 on Mono S, the hemolytic activities of the two forms in individual plasmas eluted in 3 patterns: 1) high activity at 16 mS, low activity at 30 mS; 2) low activity at 16 mS, high activity at 30 mS; 3) high activity at 16 mS, high activity at 30 mS. The specific activities of both forms were approximately the same; both eluted the same after gel filtration at pH 5.5, and both had the same pattern on SDS-PAGE and immunoblots. The pattern of elution was characteristic for each individual plasma, and the first hemolytic form appeared to elute independent of the second form. At pH 4.5, C2 was completely separated from Factor B, a functionally and structurally similar protein of the alternative complement pathway, whereas at pH 5.5 or 6.0, the two proteins eluted together. From these results, the two forms of hemolytic C2 can be purified for structural and functional analyses.

Chromatography, Ion Exchange↗
PubMed1981

Glomerular disease in two patients with urticaria-cutaneous vasculitis and hypocomplementemia.

We assessed the clinical, serologic, and renal abnormalities of two patients with the syndrome of hypocomplementemia, vasculitis, and urticaria. Both patients presented with recurrent urticaria and were found subsequently to have glomerulonephritis. Both manifested depletion of the early complement (C) components, and their Cl inhibitor levels were normal. Circulating immune complexes were detected by two of three assays in both patients. One patient had a high titer of Sm antibodies. The detectable immune complexes were of high molecular weight, and were more suggestive of classical lupus erythematosus than the low molecular weight (7S) Clq precipitins which characterize some cases of hypocomplementemia-vasculitis-urticaria syndrome. Biopsy of the skin lesions in both patients revealed leukocytoclastic vasculitis with immunoglobulin and C deposits at the dermal-epidermal junction. Renal biopsy specimens showed segmental or diffuse proliferative mesangial glomerulonephritis. The results suggest that patients with this syndrome do not conform to a discrete entity but rather exhibit a spectrum of diseases ranging from systemic lupus erythematosus to the syndrome of urticaria, hypocomplementemia, and low molecular weight Clq precipitins.

Adult↗
PubMed1978

Inhibition of four human serine proteases by substituted benzamidines.

A series of substituted benzamidines has been examined for their inhibitory activity against the human serine proteases--trypsin, thrombin, plasmin, and C1s, a subunit of the first component of complement. The inhibition constants obtained for each enzyme were correlated with physical-chemical properties of the substituent group using the quantitative structure-activity relationship approach. This analysis indicated that plasmin and C1s are very similar in their interactions with substituted benzamidines. The binding of benzamidines in both enzymes was affected by electron donation from the substituent and its hydrophobicity. Thrombin-benzamidine interaction was affected only by the hydrophobicity of the substituent. Trypsin displayed a complex interaction with substituted benzamidines, and interaction was dependent on molar refractivity and molecular weight. Certain substituents deviated significantly from the interactions predicted by the analysis. These compounds, the (m- and p-amidinophenyl)pyruvic acids, when analyzed by computer modeling, suggested that direct interaction between the substituent and the enzyme surface is important in assessing the effect of substituent groups on inhibitory activity.

Amidines↗
PubMedDate not supplied

[The mechanism of inhibition of the activation of the complement first component by polyanions and polycations ].

Polyethyleneimine (PEI, 50 kDa) and polymethacrylic acid (PMA, 200 kDa) were shown to inhibit the lysis of sheep erythrocytes induced by the guinea pig complement. They twofold suppress the hemolysis at the concentrations of 0.47 and 0.89 microgram/ml, respectively. The inhibitory effect on the binding of the C1q subunit of human complement to the sensitized sheep erythrocytes (EA) was found to depend on the component of the reaction with which the inhibitors were preliminarily incubated. When an inhibitor, C1q, and EA were simultaneously incubated, the inhibition constants for PEI and PMA were 17 +/- 6 and 8.1 +/- 0.1 micrograms/ml, respectively. The preincubation of EA with PEI and the subsequent washing out of the inhibitor resulted in the inhibition constant of 22 +/- 3 micrograms/ml. No inhibitory effect was observed after a similar preincubation of EA with PMA. No inhibition was also detected when the inhibitors were added after the formation of the C1q complex with antibodies. These observations suggest that the binding of antibodies to cationic PEI prevents the C1q-antibody complex formation, while the binding of anionic PMA to the active site of C1q impedes the interaction of this subunit with immunoglobulins. Moreover, within the range of concentrations studied, the studied inhibitors did not affect the subsequent C1q binding to the C1r and C1s enzymes.

Animals↗