Natural anti-Gal antibodies constitute 0.2% of intravenous immunoglobulin and are equally retained on a synthetic disaccharide column or on an immobilized natural glycoprotein

Barreau, Nathalie; Blancho, Gilles; Boulet, Coralie; Martineau, Adrian R.; Vusio, Patricia; Liaigre, Jérôme; Bovin, Nicolai V.; Bouhours, Danièle; Bouhours, Jean-François

doi:10.1016/s0041-1345(00)01023-x

Cited by 17 publications

(14 citation statements)

References 3 publications

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“…Keeping this in mind, our observations indicated that complement activation may require higher concentrations of IgG anti-αGal than the average concentration found in the plasma of healthy humans (approximately 10 mg/l). [8][9][10] However, we also observed that the density of cell-bound IgG anti-αGal required for CP activation decreased when the complement concentration was increased. We anticipate that 10to 100-fold higher complement concentrations in human plasma than those used in our experiments support CP activation at lower levels of IgG anti-αGal.…”

Section: Discussionmentioning

confidence: 73%

“…7 IgG antibody against terminal galactose-α-1,3-galactose (Galα3Gal) (IgG anti-αGal) is a naturally occurring antibody that is proposed to enhance bacterial infections by Abbreviations: AP, alternative pathway; CP, classical pathway; EcO86, Escherichia coli serotype O86; ED50, half-maximal effective antibody density; EDTA, ethylenediaminetetraacetic acid; Galα3Gal, galactose-, α, -1,3-galactose; hRBC, human ABO blood type O red blood cells; HSA, human serum albumin; Ig, immunoglobulin; HHS, human hypogammaglobulinaemic serum (used as complement source); IgG anti-αGal, human IgG reacting with terminal Galα3Gal; nhIgG, normal human IgG; NHS, normal human serum; P, doubling-percentage; pRBC, pig red blood cells; SD, standard deviation; Sp9V, Streptococcus pneumoniae serotype 9V; T½, half-time until plateau phase (in one-phase association model); y ∞ , Signal at plateau phase (in one-phase association model); 95% CI, 95% confidence intervals conveying protection from complement. 4 This is of particular interest as IgG anti-αGal is abundant in essentially all humans (comprising on average 0Á1% of the total IgG [8][9][10] ) and reacts with a wide range of extracellular bacterial pathogens. 4,11,12 In this light, clarification of the role of IgG anti-αGal in complement activation is imperative.…”

Section: Introductionmentioning

confidence: 99%

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Complement activation by human IgG antibodies to galactose‐α‐1,3‐galactose

et al. 2020

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Summary Some human antibodies may paradoxically inhibit complement activation on bacteria and enhance pathogen survival in humans. This property was also claimed for IgG antibodies reacting with terminal galactose‐α‐1,3‐galactose (Galα3Gal; IgG anti‐αGal), a naturally occurring and abundant antibody in human plasma that targets numerous different pathogens. To reinvestigate these effects, we used IgG anti‐αGal affinity isolated from a pool of normal human IgG and human hypogammaglobulinaemia serum as a complement source. Flow cytometry was performed to examine antibody binding and complement deposition on pig erythrocytes, Escherichia coli O86 and Streptococcus pneumoniae serotype 9V. Specific nanobodies were used to block the effect of single complement factors and to delineate the complement pathways involved. IgG anti‐αGal was capable of activating the classical complement pathway on all the tested target cells. The degree of activation was exponentially related to the density of bound antibody on E. coli O86 and pig erythrocytes, but more linearly on S. pneumoniae 9V. The alternative pathway of complement amplified complement deposition. Deposited C3 fragments covered the activating IgG anti‐αGal, obstructing its detection and highlighting this as a likely general caveat in studies of antibody density and complement deposition. The inherent capacity for complement activation by the purified carbohydrate reactive IgG anti‐αGal was similar to that of normal human IgG. We propose that the previously reported complement inhibition by IgG anti‐αGal relates to suboptimal assay configurations, in contrast to the complement activating property of the antibodies demonstrated in this paper.

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Section: Discussionmentioning

confidence: 73%

Section: Introductionmentioning

confidence: 99%

Complement activation by human IgG antibodies to galactose‐α‐1,3‐galactose

et al. 2020

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“…In sera from 10 individuals it was found that anti‐Gal IgM antibodies comprised 3.9–8% of total serum IgM [6]. Natural IgG anti‐Gal antibodies have been reported to account for 0.2% [7], 0.5% [8] or 1% [9] of total human IgG. The variation is most likely because of different methods used.…”

Section: Introductionmentioning

confidence: 99%

Human serum‐induced porcine endothelial cell E‐selectin expression is associated with IgG3 and IgM anti‐Gal antibodies

Sæthre

Sølvik

Haraldsen

et al. 2002

Xenotransplantation

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Naturally occurring anti-Galalpha1-3Gal (anti-Gal) antibodies and complement induce hyperacute rejection (HAR) of porcine organs transplanted to primates. If the hyperacute reaction is prevented, an acute vascular rejection (AVR) occurs within hours to few days. Antibodies are important for the development of AVR, whereas the role of complement is still not clarified. AVR is characterized by protein synthesis-dependent endothelial cell (EC) activation. In the present study we investigated the relation between EC activation as measured by E-selectin expression, and the concentrations of anti-Gal antibodies of IgM, IgG and IgG subclasses in sera from 80 healthy blood donors selected on the basis of sex and age. There was a significant correlation between E-selectin expression and the concentration of IgG3 anti-Gal (r=0.39; P=0.019), which was not seen for the other IgG subclasses or for total IgG anti-Gal. A modest, but significant correlation was found between the concentration of IgM anti-Gal and E-selectin expression (r=0.38; P=0.040), but not between IgM and IgG3 anti-Gal. There was a large interindividual variation in anti-Gal antibodies, 50-fold for IgM and 70-fold for IgG. Females had significantly higher concentrations of IgM anti-Gal than males (P=0.0006), which was explained by a substantial increase in IgM anti-Gal concentration in younger women. The concentration of IgG anti-Gal and the degree of E-selectin expression did not differ between sex or age groups. In conclusion, the close correlation between anti-Gal antibodies of the potent complement activating IgG3 subclass and porcine EC activation, may imply that these antibodies play a role in EC activation characteristic of AVR.

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“…To provide a broad picture of anti-αGal reactivity with pathogens, we examined binding to 100 consecutive clinical strains, diagnosed as the cause of sepsis in humans. IgG anti-αGal was used at 5 mg/L and thus slightly conservative relative to mean concentration in human plasma of approximately 10 mg/L [5][6][7] . To correct for possible unspecific immunoglobulin capture by the microorganisms (e.g., by protein A found on some Staphylococcus aureus) we tested each pathogen for capture of an irrelevant antibody (rituximab, monoclonal anti-hCD20 at 10 mg/L).…”

Section: Binding Of Igg Anti-αgal To Escherichia Coli O86 E Coli O8mentioning

confidence: 99%

Abundant human anti-Galα3Gal antibodies display broad pathogen reactivity

Jensen

Petersen

Ellerman-Eriksen

et al. 2020

Sci Rep

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Antibodies of the igG class to terminal Galα3Gal (IgG anti-αGal) is abundant in human plasma and are reported to bind most sepsis-causing Gram-negative bacteria. However, these seminal findings, made more than two decades ago, have not been reexamined. Our aim was to assess IgG anti-αGal´s pathogen reactivity. We affinity purified IgG anti-αGal from a therapeutic grade normal human igG pool applying two rounds of positive selection with Galα3Gal-coupled beads and included removal of column matrix reactive antibodies. The purified antibodies were rigorously characterized in terms of specificity and purity in various solid-phase immunoassays. We used flow cytometry to study reactivity against 100 consecutive clinical isolates diagnosed as cause of sepsis in humans. We found that the purified igG anti-αGal displays high specificity for Galα3Gal. Also, IgG anti-αGal at 5 mg/L bound 56 out of 100 pathogens with predilection for Gram-positive bacteria binding 39 out of 52 strains. We confirm that although igG anti-αGal comprise a small fraction of the human antibody pool (~0.1%), these antibodies targets an impressively large part of pathogens causing invasive disease. The increasing frequency of pathogens resistant to antibiotics poses immense global challenges 1 and novel therapeutic strategies are crucial. Over millions of years, human ancestors have evolved numerous countermeasures to pathogen threats. Our hard-earned defense mechanisms are obvious assets to build on in development of effective therapeutics to combat pathogens. Intriguingly, one group of human antibodies, IgG antibodies against the carbohydrate structure terminal Galα3Gal (IgG anti-αGal), were more than twenty years ago reported to bind most of sepsis-causing Gram-negative bacterial pathogens, including Escherichia coli and species of Klebsiella, Enterobacter, Serratia, Citrobacter, Proteus, and Pseudomonas 2,3. This broad pathogen reactivity is of interest in the context of developing new therapeutic measures. IgG anti-αGal were originally reported to comprise 1% of plasma IgG in all humans 4 , corresponding to around 100 mg/L. According to later studies, the average concentration seems to be maybe 10-fold lower 5-7 and to vary considerably between individuals (>400-fold 7). IgG anti-αGal is mainly IgG subclass 2 (IgG2) 5 in accordance with the general finding for anti-carbohydrate antibodies 8-10. Human plasma also contains anti-αGal antibodies of immunoglobulin classes A and M 11-13. It is unclear why humans produce antibodies to Galα3Gal. The antigen, Galα3Gal, is not synthesized by simians of the Catarrhini subdivision (which includes humans, other apes, and old-world monkeys) because the gene encoding the essential α1,3-galactosyltransferase was silenced in our common ancestor 14 whereas all other mammals synthesize Galα3Gal. As Galα3Gal is non-self, Catarrhini are allowed production of IgG anti-αGal which is found naturally occurring in these animals 15. The prevailing theory is that Galα3Gal-containing antigens presented to our immune syste...

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Natural anti-Gal antibodies constitute 0.2% of intravenous immunoglobulin and are equally retained on a synthetic disaccharide column or on an immobilized natural glycoprotein

Cited by 17 publications

References 3 publications

Complement activation by human IgG antibodies to galactose‐α‐1,3‐galactose

Complement activation by human IgG antibodies to galactose‐α‐1,3‐galactose

Human serum‐induced porcine endothelial cell E‐selectin expression is associated with IgG3 and IgM anti‐Gal antibodies

Abundant human anti-Galα3Gal antibodies display broad pathogen reactivity

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