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PubMed1997

Reviparin-sodium prevents complement-mediated myocardial injury in the isolated rabbit heart.

The cytoprotective action of reviparin-sodium (LU-47311: Clivarin), a low-molecular-weight heparin, was examined in an ex vivo model of complement-mediated myocardial injury. The effective concentration of reviparin was determined by using an in vitro rabbit erythrocyte-lysis assay using 4% normal human plasma. Reviparin (0.01-2.73 mg/ml) reduced erythrocyte lysis in a concentration-dependent manner. Subsequently, 0.91 mg/ml of reviparin was evaluated in an ex vivo rabbit isolated-heart model of human complement-mediated injury. Hearts perfused in the presence of 0.91 mg/ml of reviparin (n = 10) demonstrated significant preservation of ventricular function compared with vehicle-treated hearts (n = 10), as evidenced by coronary artery perfusion pressure, left ventricular developed pressure, and left ventricular end-diastolic pressure. A reduction in myocyte creatine kinase release was observed in reviparin-treated hearts compared with controls. Myocardial injury in vehicle-treated hearts was associated with an increased assembly of the membrane-attack complex, as determined by immunohistochemical localization of C5b-9 neoantigen. Reviparin decreased fluid-phase Bb formation detected in the lymphatic drainage of plasma-perfused hearts. The results of this study demonstrate that reviparin inhibits complement-mediated myocardial injury as assessed in an ex vivo experimental model of complement activation.

Animals↗
PubMed1985

Self-association of the seventh component of human complement (C7): dimerization and polymerization.

Two association reactions of isolated C7 are described. The incubation of isolated C7 in 1% deoxycholate results in hemolytically inactive dimeric C7 that has a sedimentation coefficient of 7.3S. Dimeric C7 expressed hydrophobic domains that bound 41 +/- 4 mol deoxycholate per mol C7 and that aggregated upon removal of the detergent. The dimeric nature of the deoxycholate-treated C7 was demonstrated by analytical ultracentrifugation and by gel filtration, and yielded the following parameters: Mr = 230,000; diffusion coefficient, D = 2.9 X 10(-7) cm2/sec, and Stokes' radius, rH = 7.3 nm. Dimeric C7 exhibits an increased electrophoretic mobility and an increased beta-sheet structure, as compared with monomeric C7. Upon incubation with deoxycholate-phospholipid mixed micelles and removal of the detergent, the dimeric C7 became firmly associated with the lipid vesicles and was partially aggregated in the lipid bilayer. Trypsin treatment released approximately 50% of the protein material from the C7 vesicle complex. The other association reaction of isolated C7 occurs upon incubation with 1 M guanidine HC1; C7 forms soluble, linear protein polymers that have sedimentation coefficients ranging from 20 to 30S. The strands are 5 to 8 nm wide and vary in length between 20 to 100 nm. They tend not to aggregate, they are hemolytically inactive, and they exhibit increased beta-sheet structure, as compared with monomeric C7. They can be dissociated to hemolytically active monomers by exposure to 4 M guanidine HC1 and by subsequent 100-fold dilution with buffer. Isolated C5 or C6 did not exhibit any of these properties. The results suggest that the properties acquired by C7 in the hydrophilic-amphiphilic transition may be responsible for the expression of the membrane binding site of "metastable" C5b-7 and for the polymerization of C5b-7 within the target membrane.

Complement Activation↗
PubMed1992

Dissociation of primary antigen-antibody bonds is essential for complement mediated solubilization of immune precipitates.

The role of dissociation of primary antigen-antibody bonds in the solubilization of immune complexes (IC) has been investigated using photo-affinity crosslinked IC comprising NAP15-BSA and murine monoclonal anti-DNP antibodies. Non-covalently linked IC were solubilized rapidly when incubated with normal human serum (NHS), whereas covalently-linked IC were solubilized poorly or not at all. The rate and extent of complement activation produced by incubating covalently-linked and non-covalently linked IC with NHS was similar as assessed by the production of the C1s:C1-inhibitor, C3:properdin and C5b-9 complexes and the anaphylatoxins C4a and C3a. Thus, the inability of serum to solubilize photo-affinity crosslinked IC must be due to failure of dissociation of primary antigen-antibody bonds.

Animals↗
PubMed1991

[Activation of human serum complement with inulin and purification of SC5b-9].

During a study of the effect of inulin on human complement, we found that complements were partially activated after incubation with inulin for one hour and completely activated after incubation for three hours at 37 degrees C. SC5b-9 was purified by DEAE-Sephacel chromatography, linear sucrose density gradients centrifugation and anti-IgM-protein A affinity chromatography. Purified SC5b-9, as assayed by immunoelectrophoresis, was a single fraction and had C5b, C6, C7/C8 alpha gamma, C8 beta, C9, C92, and S-protein bands appearing in the 10% SDS-PAGE.

Complement Activation↗
PubMed2001

Specific inhibition of the classical complement pathway by C1q-binding peptides.

Undesired activation of the complement system is a major pathogenic factor contributing to various immune complex diseases and conditions such as hyperacute xenograft rejection. We aim for prevention of complement-mediated damage by specific inhibition of the classical complement pathway, thus not affecting the antimicrobial functions of the complement system via the alternative pathway and the lectin pathway. Therefore, 42 peptides previously selected from phage-displayed peptide libraries on basis of C1q binding were synthesized and examined for their ability to inhibit the function of C1q. From seven peptides that showed inhibition of C1q hemolytic activity but no inhibition of the alternative complement pathway, one peptide (2J) was selected and further studied. Peptide 2J inhibited the hemolytic activity of C1q from human, chimpanzee, rhesus monkey, rat, and mouse origin, all with a similar dose-response relationship (IC(50) 2-6 microM). Binding of C1q to peptide 2J involved the globular head domain of C1q. In line with this interaction, peptide 2J dose-dependently inhibited the binding of C1q to IgG and blocked activation of C4 and C3 and formation of C5b-9 induced via classical pathway activation, as assessed by ELISA. Furthermore, the peptide strongly inhibited the deposition of C4 and C3 on pig cells following their exposure to human xenoreactive Abs and complement. We conclude that peptide 2J is a promising reagent for the development of a therapeutic inhibitor of the earliest step of the classical complement pathway, i.e., the binding of C1q to its target.

Amino Acid Sequence↗
PubMed2000

Inhibition of complement alternative pathway function with anti-properdin monoclonal antibodies.

Complement activation products appear to contribute to the pathology of several acute and chronic inflammatory conditions. The relative contributions of the classical and alternative complement pathways to these pathologies have, in large part, been undefined. Considerable progress has been made recently in identifying inhibitors of complement activation and demonstrating that such molecules can attenuate inflammation in various models of disease. However, most of these complement inhibitors affect aspects of both the classical and alternative pathways. In an effort to better define the role of the alternative complement pathway in complement-mediated inflammatory conditions, we have developed monoclonal antibodies that specifically inhibit alternative pathway function. These blocking antibodies bind human properdin with high avidity and prevent its interaction with the alternative pathway C3 convertase. This results in a cessation of alternative pathway function in several in vitro assay systems. When tested in a model of cardiopulmonary bypass, in which human blood passes through tubing, a selected antiproperdin antibody caused nearly complete inhibition of the C3a and C5b-9 formation that was seen in untreated blood. Moreover, the anti-properdin agent resulted in a dramatic reduction of neutrophil and platelet activation in the bypass model. Surprisingly, the monoclonal antibody also caused a significant inhibition of C5b-9 generation when classical pathway activators, such as heparin-protamine or immune complexes, were added to human blood. These latter data suggest that the alternative pathway contributes significantly to the formation of complement activation products in blood when the classical pathway is initially triggered.

Antibodies, Monoclonal↗
PubMed1992

Activation of human complement system Paracoccidioides brasiliensis and its deposition on the yeast form cell surface.

The yeast form of Paracoccidioides brasiliensis strain Pb18 was able to activate C3 of normal human serum diluted in phosphate-buffered saline or EGTA-MgCl2 in vitro. C3 convertase was also permissive when Pb18 cells were pre-treated with a pool of immune serum from patients with paracoccidioidomycosis and incubated in serum diluted in EDTA-CaCl2. The components C3, and fragments C3c, C3d, C3g, factor H, factor B, C4 and C5b-9 were demonstrated on the Pb18 cell surface by immunofluorescence although no effect was seen on fungal viability.

Complement Activation↗
PubMed1987

Haemolytic 'efficiency' of C5b-9 complexes in drug-induced immune haemolysis: role of cellular C5b-9 distribution.

We report on quantitative analyses of C5b-9 binding to target red blood cells (RBC) lysed through the action of drug (nomifensine)-dependent antibodies (ddab) and anti-RBC antibodies (warm plus cold agglutinins). Immunoradiometric assays showed that, at any given degree of haemolysis, more C5b-9 was bound to cells sensitized with anti-RBC antibodies compared to cells lysed via ddab. Thus, C5b-9 complexes deposited through the action of ddab appeared to be haemolytically more 'efficient' than those deposited via anti-RBC antibodies. However, data obtained from flow-cytometric assays and immunoelectron microscopy demonstrated a major role for the distribution (total number) of C5b-9 lesions among the cells within a given cell population. Enhanced haemolysis with a given total amount of C5b-9 complexes appeared to be derived from a more even distribution of these complexes among the cells rather than from higher lytic efficiency of individual complexes. Since ddab bind with low affinity to cells, we suggest that these antibodies diffuse from cell to cell and cause extensive haemolysis through the deposition of relatively few C5b-9 complexes at each site. In contrast, high affinity antibodies remain largely bound to relatively restricted sites causing deposition of larger amounts of C5b-9 on, and hence lysis of, numerically fewer cells. With respect to the net intravascular haemolytic effect, our findings may explain why complement-activating antibodies of low affinity are often more detrimental than high affinity antibodies.

Antibody Affinity↗
PubMed2000

Phase I trial of the recombinant soluble complement receptor 1 in acute lung injury and acute respiratory distress syndrome.

OBJECTIVE: To determine the safety, pharmacokinetics, biological effects, and immunogenicity of recombinant soluble complement receptor 1 (TP10) in patients with acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). DESIGN: Open label, ascending dosage, phase I trial. SETTING: Two academic teaching hospitals. PATIENTS: A total of 24 patients diagnosed with ALI/ARDS. INTERVENTION: A single, 30-min intravenous infusion of 0.1, 0.3, 1, 3, or 10 mg/kg TP10. MEASUREMENTS AND MAIN RESULTS: Serum levels of TP10 increased in proportion to the dose. Mean variable estimates (+/-SD) were half-life of disposition 69.7 +/- 39.7 hrs, plasma clearance 2.39 +/- 1.32 mL/hr/kg, and volume of distribution 190.6 +/- 135.0 mL/kg. Inhibition of complement activity, measured by CH50, was significant for the interaction of dose and time (p = .024). The C3a levels demonstrated a trend for dose which did not reach statistical significance (p = .090) and soluble C5b-9 levels were significant only for dose (p = .023). As expected by the proposed physiologic mechanism, C4a levels were not affected by TP10, dose, or time. The overall mortality rate was 33%. Neither the type nor the frequency rate of specific adverse events were substantially different between dose groups. Seven adverse events in four patients were thought to be possibly related to TP10. CONCLUSIONS: TP10 has a half-life of approximately 70 hrs and at doses > or =1 mg/kg, significantly inhibits complement activity at the levels of C3 and C5 in patients with ALI/ARDS. Complement inhibition was more prolonged over time with TP10 doses of 3 and 10 mg/kg. TP10 appears to be safe at the doses tested. Further studies will be required to completely assess the impact of TP10 on pathophysiology and clinical outcome in patients with ALI/ARDS.

Adult↗
PubMed2003

Pre-neutralization of C5a-mediated effects by the monoclonal antibody 137-26 reacting with the C5a moiety of native C5 without preventing C5 cleavage.

Complement C5a is aetiologically linked to inflammatory tissue damage in conditions like septicaemia, immune complex diseases and ischaemia-reperfusion injury. We here describe a monoclonal antibody (mAb), 137-26, that binds to the C5a moiety of human C5 and neutralizes the effects of C5a without interfering with C5 cleavage and the subsequent formation of lytic C5b-9 complex. Mouse anti-human C5 mAbs were generated and the reactivity with C5 and C5a was detected by ELISA and surface plasmon resonance. The inhibition of C5a binding to C5a receptor was studied using a radioligand binding assay. The effects of the antibody on C5a functions were examined using isolated neutrophils and a novel human whole blood model of inflammation. Haemolytic assays were used to study the effect on complement-mediated lysis. mAb 137-26 reacted with both solid- and solution-phase C5 and C5a in a dose-dependent manner with high affinity. The antibody competed C5a binding to C5a receptor and inhibited C5a-mediated chemotaxis of neutrophils. Furthermore, the antibody effectively abrogated complement-dependent E. coli-induced CD11b up-regulation and oxidative burst in neutrophils of human whole blood. mAb 137-26 was more potent than a C5a receptor antagonist and a previously described anti-C5a antibody. mAb 137-26 did not inhibit complement-mediated lysis, nor did it activate complement itself. Together, mAb 137-26 binds both the C5a moiety of native C5 and free C5a, thereby effectively neutralizing the biological effects of C5a. The antibody may have therapeutic potential in inflammatory diseases where C5a inhibition combined with an operative lytic pathway of C5b-9 is particularly desired.

Animals↗
PubMed1994

Ultrastructural studies of complement mediated cell death: a biological reaction model to plasma membrane injury.

Complement-mediated nucleated cell death has been shown to be independent of colloid-osmotic swelling. In contrast, other factors (e.g. Ca2+ influx) are of importance in the induction of cell death. In this communication, the sequential morphological features of complement-mediated cell injury have been studied by electron microscopy and compared with biochemical data (ATP content and LDH release). It was observed that immediately after C5b-8 lesion formation, although the overall cell, morphology is well preserved, the mitochondria display an "ultracondensed" appearance. Upon addition of C9, the mitochondria remain initially condensed, but swell progressively with final formation of flocculent densities. The nuclei become progressively edematous, with concurrent disappearance of heterochromatin. The nucleoli lose their associated chromatin and display segregation of their components with formation of markedly electron-dense filamentous deposits. The nuclear envelope remains initially intact, but subsequently progressive dilatation of the associated perinuclear RER cisterna and distention of the nuclear pores associated with leakage of chromatin into the cytoplasm are seen. The larger cell organelles (including mitochondria, ER, Golgi apparatus, etc.) become clustered around the nucleus, concurrently with marked edema of the outer cytoplasm and bleb formation. The RER cisternae become dilated, whereas the Golgi complex disappears. Relatively early on the plasma membrane shows breaks in continuity. The pattern of these changes--potentially related to Ca2+ influx, ATP efflux and overall metabolic depletion--corresponds to the previously described model of cell reaction to injury, confirming the dynamic nature of the process. The morphology of cell death in this model shares some features, e.g., the nucleolar changes, with "apoptosis" (programmed cell death). However, the overall pattern appears to correspond more to "necrosis," characterized by loss of volume control and mitochondrial abnormalities.

Adenosine Triphosphate↗
PubMed1987

Role of complement C9 and calcium in the generation of arachidonic acid and its metabolites from rat polymorphonuclear leukocytes.

We have previously shown that antibody-sensitized mouse peritoneal macrophages release arachidonic acid (C20:4) and its oxygenated derivatives when treated with complement, and that the major part of the release depended on the terminal complement complexes (TCC). To further delineate the process(es) responsible for this release we have extended our studies to rat peritoneal polymorphonuclear leukocytes (PMNs). Experiments were performed with antibody-sensitized rat PMNs labeled with [3H]C20:4 and carrying the TCC, C5b-7, C5b-8 or C5b-9. In contrast to the results of other studies, production of leukotriene B4 (LTB4), the major radiolabeled derivative, was strictly dependent on the presence of C9. However, low levels of C20:4 and prostaglandins (PGs) were produced prior to the C5b-9 stage. Kinetic studies demonstrated that release of LTB4 was rapid; the initial release occurred within 4-6 min and a second rise in release coincided with cell death. Virtually all the LTB4 produced was released as we found no evidence of retention of intracellular LTB4 at either the C5b-8 or C5b-9 stages. In the absence of extracellular calcium, the release of LTB4 was completely abolished and the release of C20:4 and PGs was drastically reduced. [3H]C20:4-labeled PMNs carrying C5b-9 did release substantial amounts of radiolabeled material in the presence of EGTA; however, the majority of this lipid was in the form of intact phospholipid and triglyceride. These results indicate that release of C20:4 and its oxygenated derivatives from rat PMNs is (1) dependent on the participation of C9 in the preexisting C5b-8 complex in the cell membrane, and (2) largely dependent on the presence of calcium.

Animals↗
PubMed1997

Immunocytochemical detection of anti-hippocampal antibodies in Alzheimer's disease and normal cerebrospinal fluid.

Immunocytochemical staining was performed to investigate the presence of anti-hippocampal antibodies in cerebrospinal fluid (CSF) from patients with probable Alzheimer's disease (AD) (n = 19), aged normal controls (n = 9), and young normal controls (n = 10). Marked staining of neurons in the granule cell layer of the dentate gyrus and in pyramidal neurons in CA1-3 of the rat hippocampus was observed in 5 AD CSF samples (26%), 1 aged control sample (11%), and 1 young control sample (10%). These differences were not statistically significant. One of the immunoreactive AD CSF specimens also contained high concentrations of C5b-9, the membrane attack complex. The infrequent occurrence of anti-hippocampal antibodies in AD CSF, and the detection of similar immunoreactivity in control CSF specimens, suggest that these antibodies are unlikely to play a role in the neurodegenerative process in most individuals with AD. However, elevated C5b-9 concentration in an AD CSF specimen with marked immunoreactivity to hippocampal neurons suggests the possibility that anti-neuronal antibodies may contribute to complement activation in some AD patients.

Adult↗
PubMed1999

Crry, a complement regulatory protein, modulates renal interstitial disease induced by proteinuria.

UNLABELLED: Crry, a complement regulatory protein, modulates renal interstitial disease induced by proteinuria. BACKGROUND: Recent studies have suggested a role for urinary complement components in mediating tubulointerstitial damage, which is known to have a good correlation with progression of chronic renal diseases. Although accumulating evidence suggests that complement regulatory proteins play an important protective role in glomeruli, their role in renal tubules remains unclear. In order to establish the role of a complement regulatory protein, Crry, in renal tubular injury, we employed a molecular biological approach to block the expression of Crry in tubules of animals with proteinuria induced with puromycin aminonucleoside nephritis (PAN). Methods and Results. Two different antisense oligodeoxynucleotides (ODNs) against Crry were designed and applied to cultured rat mesangial cells in vitro in order to establish their efficacy. Antisense ODN treatment resulted in decreased expression of Crry protein associated with increased sensitivity to complement attack in cell lysis assays compared with control ODN treatment or no treatment (44.7, 1.50, and 1.34%, respectively). Antisense ODNs did not affect the expression of Thy1 as a control, confirming the specificity of our ODNs. In vivo, we performed selective right renal artery perfusion to administer antisense ODNs to the kidney and showed prominent uptake of ODNs by proximal tubular cells. Reduced expression of Crry protein was demonstrated in proximal tubular cells in antisense ODNs-treated kidneys. Normal rats treated with the antisense ODNs did not show any pathological changes. However, in PAN, rats with massive proteinuria showed increased deposition of C3 and C5b-9 in tubules in antisense-treated kidneys, and histological assessment revealed more severe tubulointerstitial injury in antisense-treated animals compared with controls. CONCLUSION: These results establish a pathogenic role for complement in leading to tubulointerstitial injury during proteinuria and, to our knowledge for the first time, show a protective role of a complement regulatory protein, Crry, in renal interstitial disease.

Animals↗
PubMed1996

Terminal components of carp complement constituting a membrane attack complex.

The membrane attack complex (MAC) of carp complement was extracted with deoxycholate from rabbit erythrocytes lysed by carp serum and purified by a two-step chromatographic procedure. On two-dimensional SDS-PAGE of carp MAC, eight bands were detected. The band of M(r) 91,000 was identified as carp C9 by western blotting using anti-carp C9, and two bands of M(r) 62,000 and one band of M(r) 22,000 were confirmed as those of carp C8 alpha, C8 beta and C8 gamma, respectively, by their N-terminal amino acid sequences. The bands of M(r) 102,000 and 73,000, which generated from a 180,000 band under reducing conditions, were those corresponding to human C5b alpha and C5b beta, respectively. The remaining bands of M(r) 115,000 and 106,000 were identified as those corresponding to human C6 and C7, as determined by their molecular size, single-chain structures and similarities in N-terminal amino acid sequences to their mammalian counterparts. Densitometric scan of the gels showed the molar ratio of C5b, C6, C7, C8 and C9 in carp MAC to be 1:1:1:1:4. Based on these results, it appears that, as with mammals, the cytolytic pathway of bony fish complement is composed of five terminal components from C5 to C9.

Amino Acid Sequence↗
PubMed1990

Decay-accelerating factor regulates complement-mediated damage in the human atherosclerotic wall.

Decay-accelerating factor (DAF) is an intrinsic membrane inhibitor that regulates the activity of C3 and C5 convertases of the classical and alternative complement pathways. Using two monoclonal antibodies, IC6 and IA10, DAF was localized by immunohistochemistry using streptavidin-biotin-peroxidase complex or silver-intensified immunogold techniques in aortic, iliac and femoral samples obtained at surgery and autopsy from 32 patients. DAF was localized on the cells and in the connective tissue matrix of the arterial wall. Fibrous plaques and intimal thickenings presented larger amounts than fatty streaks, intimae and normal areas. By Western blotting analysis, DAF extracted from the arterial wall had a molecular weight of about 67 kDa. Using a double-labeling technique, DAF and C5b-9 complexes were co-localized on nucleated cells and on cell debris. The cells isolated after enzyme digestion of the arterial wall were tested for the protective role of DAF to complement-mediated damage. When DAF of the sensitized cells was blocked by monoclonal antibodies, complement-mediated cell lysis was enhanced from 10-15% to 60-70%. The effect of anti-DAF antibodies was dose-dependent. DAF blocking in the absence of antibodies used for sensitization led to a lysis under 10%. These data suggest a protective role of DAF against autologous complement activation, however insufficient to prevent complement activation in the human atherosclerotic wall.

Adult↗
PubMed1992

Sub-minimal inhibitory concentrations of cefmetazole enhance serum bactericidal activity in vitro by amplifying poly-C9 deposition.

Serum-resistant organisms grown in sub-minimal inhibitory concentrations (subMICs) of antibiotics in vitro may be rendered sensitive to complement-mediated, serum bactericidal activity. We measured 125I-C3 and 125I-C9 deposition on genetically serum resistant Salmonella montevideo SH5770 (SH5770) that was rendered serum sensitive by growth in sub-MICs of cefmetazole (CMZ), a parenteral, second generation, cephamycin-group antibiotic. Three times as much C3 and over six times as much C9 bound to SH5770 grown in one-fourth the MIC of CMZ compared to broth-grown bacteria. SDS-PAGE analysis and autoradiography showed that neither the ratio of C3b:iC3b (approximately 1:2.5) nor the nature of the C3-bacterial bond was changed by growing the organisms in CMZ. Large amounts of complement membrane attack complexes containing poly-C9 were seen only on CMZ-grown SH5770 by SDS-PAGE and autoradiography. Poly-C9 was also detected only on CMZ-grown bacteria by indirect immunofluorescence and ELISA using a murine monoclonal antibody directed against a neoantigen of poly-C9. Bacterial hydrophobicity increased after growth in CMZ, and transmission electron micrographs of CMZ-grown SH5770 showed cell wall disruption and blebbing. These results indicate that growth in subMICs of CMZ increases bacterial hydrophobic domains available for interacting with the membrane attack complex, C5b-9, allowing formation and stable insertion of bactericidal complexes containing poly-C9.

Blood Bactericidal Activity↗
PubMed1998

The complement-activating capacity of maternal IgG antibodies to blood group A in paired mother/child serum samples.

BACKGROUND AND OBJECTIVES: The aim of this study was to investigate whether IgG antibodies to blood group A bind or activate complement after crossing the placenta. MATERIALS AND METHODS: IgG anti-A concentrations as well as C1-q-binding and the capacity of anti-A to form the C5b-9 membrane attack complex were measured in sera of 61 mother/child pairs. The enzyme-linked immunosorbent assay was used to quantitate anti-A or anti-B in maternal and neonatal serum samples. RESULTS: The concentrations of IgG anti-A in ABO-identical and ABO-compatible children born to type O or B mothers correlated significantly with maternal concentrations (p < 0.05), whereas type A or AB children had strikingly diminished concentrations of IgG anti-A. The IgG anti-A concentrations were analyzed in two different groups: first, 44 mother/child pairs with mothers and children group O or B (group I), and second, 17 pairs with mothers group O or B and children group A or AB (group II). In group I, identical or compatible pairs with regard to IgG anti-A, a significant correlation was found by Spearman's rank analysis, whereas the same analysis revealed no significant correlation in group II. The capacity of anti-A to activate complement was also more marked in newborns who were ABO-identical or ABO-compatible with their mothers, and this capacity was virtually absent in cord blood samples from incompatible babies. CONCLUSIONS: Tests for complement-dependent or complement-independent ABO blood group antibodies must be interpreted in the light of the blood group of the child.

ABO Blood-Group System↗