Cellular surface plasmon resonance-based detection of anti-HPA-1a antibody glycosylation in fetal and neonatal alloimmune thrombocytopenia.

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) can occur due to maternal IgG antibodies targeting platelet antigens, causing life-threatening bleeding in the neonate. However, the disease manifests itself in only a fraction of pregnancies, most commonly with anti-HPA-1a antibodies. We found that in particular, the core fucosylation in the IgG-Fc tail is highly variable in anti-HPA-1a IgG, which strongly influences the binding to leukocyte IgG-Fc receptors IIIa/b (FcγRIIIa/b).

The Influence of Human IgG Subclass and Allotype on Complement Activation.

Complement activation via the classical pathway is initiated when oligomeric Igs on target surfaces are recognized by C1 of the complement cascade. The strength of this interaction and activation of the complement system are influenced by structural variation of the Ab, including Ab isotype, subclass, and glycosylation profile. Polymorphic variants of IgG have also been described to influence Fc-dependent effector functions.

Prevention of Fetal/Neonatal Alloimmune Thrombocytopenia in Mice: Biochemical and Cell Biological Characterization of Isoforms of a Human Monoclonal Antibody.

Maternal alloantibodies toward paternally inherited Ags on fetal platelets can cause thrombocytopenia and bleeding complications in the fetus or neonate, referred to as fetal and neonatal alloimmune thrombocytopenia (FNAIT). This is most commonly caused by Abs against the human platelet Ag (HPA)-1a in Caucasians, and a prophylactic regimen to reduce the risk for alloimmunization to women at risk would be beneficial. We therefore aimed to examine the prophylactic potential of a fully human anti-HPA-1a IgG1 (mAb 26.

Augmented antibody-based anticancer therapeutics boost neutrophil cytotoxicity.

Most clinically used anticancer mAbs are of the IgG isotype, which can eliminate tumor cells through NK cell-mediated antibody-dependent cellular cytotoxicity and macrophage-mediated antibody-dependent phagocytosis. IgG, however, ineffectively recruits neutrophils as effector cells. IgA mAbs induce migration and activation of neutrophils through the IgA Fc receptor (FcαRI) but are unable to activate NK cells and have poorer half-life.

Cross-reactivity of mouse IgG subclasses to human Fc gamma receptors: Antibody deglycosylation only eliminates IgG2b binding.

Immunoglobulin G (IgG) antibodies are important for protection against pathogens and exert effector functions through binding to IgG-Fc receptors (FcγRs) on myeloid and natural killer cells, resulting in destruction of opsonized target cells. Despite interspecies differences, IgG subclasses and FcγRs show substantial similarities and functional conservation between mammals. Accordingly, binding of human IgG (hIgG) to mouse FcγRs (mFcγRs) has been utilized to study effector functions of hIgG in mice.

IgG Subclass Determines Suppression Versus Enhancement of Humoral Alloimmunity to Kell RBC Antigens in Mice.

It has long been appreciated that immunoglobulins are not just the effector endpoint of humoral immunity, but rather have a complex role in regulating antibody responses themselves. Donor derived anti-RhD IgG has been used for over 50 years as an immunoprophylactic to prevent maternal alloimmunization to RhD. Although anti-RhD has dramatically decreased rates of hemolytic disease of the fetus and newborn (for the RhD alloantigen), anti-RhD also fails in some cases, and can even paradoxically enhance immune responses in some circumstances.

FcγR Binding and ADCC Activity of Human IgG Allotypes.

Antibody dependent cellular cytotoxicity (ADCC) is an Fc-dependent effector function of IgG important for anti-viral immunity and anti-tumor therapies. NK-cell mediated ADCC is mainly triggered by IgG-subclasses IgG1 and IgG3 through the IgG-Fc-receptor (FcγR) IIIa. Polymorphisms in the immunoglobulin gamma heavy chain gene likely form a layer of variation in the strength of the ADCC-response, but this has never been studied in detail.

FcγRIIIb Restricts Antibody-Dependent Destruction of Cancer Cells by Human Neutrophils.

The function of the low-affinity IgG-receptor FcγRIIIb (CD16b), which is uniquely and abundantly expressed on human granulocytes, is not clear. Unlike the other Fcγ receptors (FcγR), it is a glycophosphatidyl inositol (GPI) -anchored molecule and does not have intracellular signaling motifs. Nevertheless, FcγRIIIb can cooperate with other FcγR to promote phagocytosis of antibody-opsonized microbes by human neutrophils.

Multiplex blood group typing by cellular surface plasmon resonance imaging.

Background: Blood-group typing of donors and patients is essential to avoid incompatible transfusions. Transfusion of incompatible RBCs may result in alloimmunization complicating future transfusions or in the presence of antibodies in adverse reactions. With more than 300 blood group antigens identified, it is difficult to provide fully compatible blood.

Decoding the Human Immunoglobulin G-Glycan Repertoire Reveals a Spectrum of Fc-Receptor- and Complement-Mediated-Effector Activities.

Glycosylation of the immunoglobulin G (IgG)-Fc tail is required for binding to Fc-gamma receptors (FcγRs) and complement-component C1q. A variety of IgG1-glycoforms is detected in human sera. Several groups have found global or antigen-specific skewing of IgG glycosylation, for example in autoimmune diseases, viral infections, and alloimmune reactions.

Anaphylatoxin C5a Regulates 6-Sulfo-LacNAc Dendritic Cell Function in Human through Crosstalk with Toll-Like Receptor-Induced CREB Signaling.

Activation of antigen-presenting dendritic cells (DCs) and the complement system are essential early events in the immune defense against invading pathogens. Recently, we and others demonstrated immunological crosstalk between signaling from receptors recognizing complement activation products and PAMPs on DCs. This affects DC effector function, as demonstrated by the finding that C5a prevents induction of pro-inflammatory cytokines by toll-like receptor (TLR) ligands in human monocyte-derived DCs (moDCs).

Enhanced Effector Functions Due to Antibody Defucosylation Depend on the Effector Cell Fcγ Receptor Profile.

Abs of the IgG isotype are glycosylated in their Fc domain at a conserved asparagine at position 297. Removal of the core fucose of this glycan greatly increases the affinity for FcγRIII, resulting in enhanced FcγRIII-mediated effector functions. Normal plasma IgG contains ∼94% fucosylated Abs, but alloantibodies against, for example, Rhesus D (RhD) and platelet Ags frequently have reduced fucosylation that enhances their pathogenicity.

Affinity of human IgG subclasses to mouse Fc gamma receptors.

Human IgG is the main antibody class used in antibody therapies because of its efficacy and longer half-life, which are completely or partly due to FcγR-mediated functions of the molecules. Preclinical testing in mouse models are frequently performed using human IgG, but no detailed information on binding of human IgG to mouse FcγRs is available. The orthologous mouse and human FcγRs share roughly 60-70% identity, suggesting some incompatibility.

Monophosphoryl lipid A-induced pro-inflammatory cytokine expression does not require CD14 in primary human dendritic cells.

Objective: To elucidate if TLR4-mediated MyD88 and TRIF signalling by the clinically applicable Lipopolysaccharide (LPS)-derivative monophosphoryl lipid A (MPLA) in primary human dendritic cells requires LPS cofactors LPS-binding protein (LBP) and CD14.

Methods: Cytokine production by monocyte-derived DCs stimulated with MPLA or LPS was determined using ELISA. To investigate involvement of CD14 for action of LPS or MPLA, CD14 was inhibited using blocking antibodies or down-modulated using specific siRNA.

Comparison of media and serum supplementation for generation of monophosphoryl lipid A/interferon-γ-matured type I dendritic cells for immunotherapy.

Background Aims: Ex vivo-generated monocyte-derived dendritic cells (DCs) matured with monophosphoryl lipid A (MPLA) and interferon-γ (IFN-γ) can be used as cancer immunotherapy. MPLA/IFN-γ DCs induce Th1 T cell responses and have migratory capacity. Different culture regimens have been used for generation of immunotherapeutic DCs, with varying results.

TLR4-mediated pro-inflammatory dendritic cell differentiation in humans requires the combined action of MyD88 and TRIF.

TLR4 ligation can activate both the MyD88 and the Toll-IL-1 receptor domain-containing adaptor inducing IFN-β (TRIF) signaling route. Whereas MyD88 is generally recognized as a universal adaptor for pro-inflammatory responses, TRIF is mainly thought to contribute to specific type I IFN responses. Here, we investigated the contribution of both MyD88 and TRIF to TLR4-mediated pro-inflammatory dendritic cell (DC) differentiation in human.

Circulating bone morphogenetic protein levels and delayed fracture healing.

Objective: Despite adequate treatment 5-30% of bone fracture patients experience delayed union. During normal fracture union, bone morphogenetic proteins (BMPs) induce healing through a sequential cascade of events. Improved fracture healing after BMP-2 or -7 supplementation in patients with impaired fracture union suggests a deficiency of one or more of these factors.

Crosstalk between Toll like receptors and C5a receptor in human monocyte derived DCs suppress inflammatory cytokine production.

The complement anaphylatoxin, C5a has been implicated in regulation of adaptive immune responses through modulation of APC function as shown mainly in studies in mice. C5a was shown to enhance cytokine production in immature DCs, but the effect of C5a on DC function during DC activation has not been elucidated in human. In this study we investigated the effect of C5a on human monocyte derived DCs when simultaneously stimulated with TLR ligands.

Use and efficacy of bone morphogenetic proteins in fracture healing.

Purpose: This review evaluates the application of bone morphogenetic proteins (BMPs) in delayed bone repair, aiming at a broad audience from clinicians to scientists. Next to an overview of the role of the different BMPs, their antagonists and their current applications, special attention is focused on new scientific developments improving the effects of BMP-based therapy for bone repair.

Methods: Publication searches in PubMed and Embase revealed 850 relevant articles on the criteria 'BMP' AND 'bone repair' (as of May 2011).