Inhibition of FcγR-mediated phagocytosis by IVIg is independent of IgG-Fc sialylation and FcγRIIb in human macrophages

Nagelkerke, Sietse Q.; Dekkers, Gillian; Kustiawan, Iwan; Bovenkamp, Fleur S. van de; Geissler, Judy; Plomp, Rosina; Wuhrer, Manfred; Vidarsson, Gestur; Rispens, Theo; Berg, Timo K. van den; Kuijpers, Taco W.

doi:10.1182/blood-2014-05-576835

Cited by 93 publications

(104 citation statements)

References 45 publications

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“…Monocyte-derived macrophages were cultured for 9 days with either macrophage colony-stimulating factor (M-CSF) or granulocyte-macrophage colony-stimulating factor (GM-CSF) from monocytes isolated from heparin blood of healthy controls, as previously described. 8 …”

Section: Preparation Of Blood Leukocytes and Monocyte-derived Macrophmentioning

confidence: 99%

“…1,6 However, splenic macrophages have been poorly characterized thus far in humans, especially with regard to FcgR expression. Functional studies of IgG-mediated phagocytosis in humans often use monocyte-derived macrophages instead 7,8 because they are readily available. However, because it is not well known whether these macrophages are similar to splenic macrophages, the relevance of such studies can be debated.…”

Section: Introductionmentioning

confidence: 99%

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Red pulp macrophages in the human spleen are a distinct cell population with a unique expression of Fc-γ receptors

et al. 2018

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Section: Preparation Of Blood Leukocytes and Monocyte-derived Macrophmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Red pulp macrophages in the human spleen are a distinct cell population with a unique expression of Fc-γ receptors

et al. 2018

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“…20,21 All blood was obtained after informed consent and according to the 1964 Declaration of Helsinki. splenocytes) under various conditions.…”

Section: Isolation Of Human Neutrophils and Monocytesmentioning

confidence: 99%

“…Bone marrow neutrophils were isolated from femurs of 2-to 4-month-old mice, using a Percoll gradient as previously described, 26 and were resuspended at 5 3 10 6 /mL in cold Hank balanced salt solution (HBSS) containing Ca 21 and Mg …”

Section: Phagocytosis Experiments In Mice In Vitromentioning

confidence: 99%

Human and murine splenic neutrophils are potent phagocytes of IgG-opsonized red blood cells

et al. 2017

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Key Points• In steady state, where no IgGs against RBCs are present, macrophages are the primary phagocytes of RBCs.• In conditions where RBCs are IgGopsonized, neutrophils can have a major effect on RBC clearance.Red blood cell (RBC) clearance is known to occur primarily in the spleen, and is presumed to be executed by red pulp macrophages. Erythrophagocytosis in the spleen takes place as part of the homeostatic turnover of RBCs to remove old RBCs. It can be strongly promoted by immunoglobulin G (IgG) opsonization of RBCs, a condition that can occur as a consequence of autoantibody or alloantibody formation. The purpose of our study was to investigate which phagocytes are involved in IgG-mediated RBC clearance in the human spleen. We developed a highly specific in vitro assay to monitor RBC phagocytosis in total human splenocytes. Surprisingly, we have found that whereas homeostatic clearance of RBCs is primarily a task for splenic macrophages, neutrophils and, to a lesser extent, also monocytes can be a major factor in clearance of IgG-opsonized RBCs. Erythrophagocytosis by neutrophils is strongly dependent on the degree of opsonization of the RBCs. Additionally, the process is enhanced after blocking the "do not eat me" signal CD47 on the opsonized RBCs, which binds signal regulatory protein a, a myeloid inhibitory receptor that restricts phagocytosis. Moreover, RBCs isolated from autoimmune hemolytic anemia patients, opsonized by auto-IgGs, were shown to be readily phagocytosed by neutrophils. Finally, priming of neutrophils by inflammatory mediators such as tumor necrosis factor a and lipopolysaccharide further increases the magnitude of erythrophagocytosis. Collectively, our data suggest that neutrophils contribute significantly to the phagocytosis of antibody-opsonized RBCs, especially under inflammatory conditions. This indicates a hereto unanticipated contribution of neutrophils in RBC phagocytosis, especially under pathological conditions such as alloimmunization or autoimmunization.

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“…These findings are in keeping with data suggesting that different degrees of Fc multimerization are required to elicit FcgR and complement-mediated effects. For example, recent studies revealed the dimeric fraction of IVIG has increased ability of blocking Fc-FcgR interaction over IVIG monomers in macrophage phagocytosis, and a separate report suggested that C1q activation required the formation IgG hexamers (40,41). Consistent with these findings, whereas both lower-and higher-order fractions of GB4542 demonstrated decreased ADCP effect at higher concentrations, decreased CDC activity was observed only in the presence of high concentration of higher m.w.…”

Section: Discussionmentioning

confidence: 71%

Anti-CD20 Antibody with Multimerized Fc Domains: A Novel Strategy To Deplete B Cells and Augment Treatment of Autoimmune Disease

Zhang

Olsen

Chen

et al. 2016

The Journal of Immunology

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We developed a fully recombinant anti-CD20 protein derived from cDNA encoding one Fab domain, two IgG1 Fc regions, the IgG2 hinge, and an isoleucine zipper. This protein, called GB4542, contained both the homodimer and higher-order multimers. Binding studies revealed that GB4542 preferentially bound CD20+ cells yet also recognized CD20−FcγR+ PBMC. In contrast, a control mAb containing the identical Fab region, GB4500, failed to bind CD20−FcγR+ PBMC. Consistent with these findings, interactions between GB4542 and the canonical FcγRs had substantially lower KD values than correlate interfaces between GB4500 and these receptors. At low concentrations, GB4542 showed enhanced Ab-dependent cellular cytotoxicity, Ab-dependent cellular phagocytosis, and complement-dependent cytotoxicity compared with GB4500. However, at higher concentrations, an Fc analog of GB4542 inhibited anti-CD20 mAb–mediated B cell clearance through direct blocking of both Fc–FcγR interactions and C1q deposition on target cells. Furthermore, the higher-order multimer fraction of GB4542 demonstrated greater binding avidity with the canonical FcγRs and was associated with inhibitory effects observed in Ab-dependent cellular phagocytosis and complement-dependent cytotoxicity assays. These data suggest that GB4542 might have utility in the treatment of autoimmune diseases by combining both mAb-mediated B cell depletion and multimerized Fc-mediated tolerogenic effects.

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Inhibition of FcγR-mediated phagocytosis by IVIg is independent of IgG-Fc sialylation and FcγRIIb in human macrophages

Abstract: Key Points Phagocytosis of IgG-opsonized blood cells by human macrophages is inhibited by intravenous immunoglobulins. This inhibition is independent of IgG-Fc sialylation but improves with IgG preparations that bind FcγRs more avidly.

Cited by 93 publications

References 45 publications

Red pulp macrophages in the human spleen are a distinct cell population with a unique expression of Fc-γ receptors

Red pulp macrophages in the human spleen are a distinct cell population with a unique expression of Fc-γ receptors

Human and murine splenic neutrophils are potent phagocytes of IgG-opsonized red blood cells

Anti-CD20 Antibody with Multimerized Fc Domains: A Novel Strategy To Deplete B Cells and Augment Treatment of Autoimmune Disease

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