The Role of Complement Activation in IgM M-Protein-Associated Neuropathies.

Background And Objectives: Polyneuropathy associated with an immunoglobulin M (IgM) monoclonal gammopathy is characterized by slowly progressive, predominantly distal sensorimotor deficits, sensory ataxia, and electrophysiologic features of demyelination. IgM antibodies against myelin-associated glycoprotein (MAG) are present in serum from most patients. Nerve damage most likely results from the concerted action of binding of anti-MAG antibodies to nerves, followed by complement activation.

Complement activation by IgM autoantibodies linked to immune-mediated neuropathies depends on C2.

Background And Purpose: Complement factor C2 is a potential therapeutic target in immune-mediated neuropathies. However, literature suggests that classical complement pathway activation may proceed to C3 in the absence of C2, a so-called "C2 bypass." Here, we evaluated a C2 bypass mechanism during complement activation by pathogenic human IgM from patients with immune-mediated neuropathies.

IgM anti-GM2 antibodies in patients with multifocal motor neuropathy target Schwann cells and are associated with early onset.

Background: Multifocal motor neuropathy (MMN) is a rare, chronic immune-mediated polyneuropathy characterized by asymmetric distal limb weakness. An important feature of MMN is the presence of IgM antibodies against gangliosides, in particular GM1 and less often GM2. Antibodies against GM1 bind to motor neurons (MNs) and cause damage through complement activation.

A 21-bp deletion in the complement regulator CD55 promotor region is associated with multifocal motor neuropathy and its disease course.

Background And Aims: To further substantiate the role of antibody-mediated complement activation in multifocal motor neuropathy (MMN) immunopathology, we investigated the distribution of promotor polymorphisms of genes encoding the membrane-bound complement regulators CD46, CD55, and CD59 in patients with MMN and controls, and evaluated their association with disease course.

Methods: We used Sanger sequencing to genotype five common polymorphisms in the promotor regions of CD46, CD55, and CD59 in 133 patients with MMN and 380 controls. We correlated each polymorphism to clinical parameters.

Multifocal motor neuropathy is not associated with altered innate immune responses to endotoxin.

Objective: Antibody- and complement-mediated peripheral nerve inflammation are central in the pathogenesis of MMN. Here, we studied innate immune responses to endotoxin in patients with MMN and controls to further our understanding of MMN risk factors and disease modifiers.

Methods: We stimulated whole blood of 52 patients with MMN and 24 controls with endotoxin and collected plasma.

Targeting the high affinity receptor, FcγRI, in autoimmune disease, neuropathy, and cancer.

The Fc gamma receptor I (FcγRI or CD64) is the only human Fc receptor with a high affinity for monomeric IgG. It plays a crucial role in immunity, as it mediates cellular effector functions of antibodies including phagocytosis, antigen presentation, and cytokine production. FcγRI is constitutively saturated with monomeric IgG and this feeds the dogma that it has no role in immune responses.

Anti-C2 Antibody ARGX-117 Inhibits Complement in a Disease Model for Multifocal Motor Neuropathy.

Background And Objectives: To determine the role of complement in the disease pathology of multifocal motor neuropathy (MMN), we investigated complement activation, and inhibition, on binding of MMN patient-derived immunoglobulin M (IgM) antibodies in an induced pluripotent stem cell (iPSC)-derived motor neuron (MN) model for MMN.

Methods: iPSC-derived MNs were characterized for the expression of complement receptors and membrane-bound regulators, for the binding of circulating IgM anti-GM1 from patients with MMN, and for subsequent fixation of C4 and C3 on incubation with fresh serum. The potency of ARGX-117, a novel inhibitory monoclonal antibody targeting C2, to inhibit fixation of complement was assessed.

Anti-GD2 IgA kills tumors by neutrophils without antibody-associated pain in the preclinical treatment of high-risk neuroblastoma.

Background: The addition of monoclonal antibody therapy against GD2 to the treatment of high-risk neuroblastoma led to improved responses in patients. Nevertheless, administration of GD2 antibodies against neuroblastoma is associated with therapy-limiting neuropathic pain. This severe pain is evoked at least partially through complement activation on GD2-expressing sensory neurons.

ARGX-117, a therapeutic complement inhibiting antibody targeting C2.

Background: Activation of the classical and lectin pathway of complement may contribute to tissue damage and organ dysfunction of antibody-mediated diseases and ischemia-reperfusion conditions. Complement factors are being considered as targets for therapeutic intervention.

Objective: We sought to characterize ARGX-117, a humanized inhibitory monoclonal antibody against complement C2.

A Single Nucleotide C3 Polymorphism Associates With Clinical Outcome After Lung Transplantation.

Development of chronic rejection is still a severe problem and causes high mortality rates after lung transplantation (LTx). Complement activation is important in the development of acute rejection (AR) and bronchiolitis obliterans syndrome, with C3 as a key complement factor. We investigated a single nucleotide polymorphism (SNP) in the C3 gene (rs2230199) in relation to long-term outcome after LTx in 144 patient-donor pairs.

The Autoimmune-Associated Single Nucleotide Polymorphism Within Correlates With Clinical Outcome After Lung Transplantation.

Obstructive chronic lung allograft dysfunction (BOS) is the major limiting factor for lung transplantation (LTx) outcome. is described as the hallmark autoimmunity gene, and one specific single nucleotide polymorphism (SNP), rs2476601, is associated with multiple autoimmune diseases, impaired T cell regulation, and autoantibody formation. Taking into consideration the contribution of autoimmunity to LTx outcome, we hypothesized that polymorphisms in the gene could be associated with BOS incidence.

Reduced Expression of Membrane Complement Regulatory Protein CD59 on Leukocytes following Lung Transplantation.

Cellular protection against undesired effects of complement activation is provided by expression of membrane-bound complement regulatory proteins including CD59. This protein prevents membrane attack complex formation and is considered to be involved in graft accommodation. Also, CD59 downregulates CD4+ and CD8+ T-cell activation and proliferation.

Association between a Single Donor Promotor Polymorphism and Obstructive Chronic Lung Allograft Dysfunction after Lung Transplantation.

Lung transplantation (LTx) outcome is hampered by development of chronic rejection, often manifested as the bronchiolitis obliterans syndrome (BOS). Low serum levels of thymus and activation-regulated chemokine (TARC/CCL17), a chemoattractant, measured during the first month post-LTx are predictive for BOS development. Since promotor polymorphisms correlate with serum TARC/CCL17 levels, we investigated seven single-nucleotide polymorphisms (SNPs) within this region and their potential association with LTx outcome.

Antibodies against Apoptotic Cells Present in End-stage Lung Disease Patients Do Not Correlate with Clinical Outcome after Lung Transplantation.

Antibodies against HLA and non-HLA are associated with transplantation outcome. Recently, pretransplant serum IgG antibody levels against apoptotic cells were found to correlate with kidney allograft loss. We investigated the presence of these antibodies in lung transplantation (LTx) patients and evaluated the correlation of pre-LTx serum levels of IgG antibodies against apoptotic cells with LTx outcome.

Soluble CD59 is a Novel Biomarker for the Prediction of Obstructive Chronic Lung Allograft Dysfunction After Lung Transplantation.

CD59 is a complement regulatory protein that inhibits membrane attack complex formation. A soluble form of CD59 (sCD59) is present in various body fluids and is associated with cellular damage after acute myocardial infarction. Lung transplantation (LTx) is the final treatment for end-stage lung diseases, however overall survival is hampered by chronic lung allograft dysfunction development, which presents itself obstructively as the bronchiolitis obliterans syndrome (BOS).

Profiling of peripheral blood mononuclear cells does not accurately predict the bronchiolitis obliterans syndrome after lung transplantation.

After lung transplantation (LTx), circulating mononuclear cell composition and their subsets may be predictive for the bronchiolitis obliterans syndrome (BOS). We investigated the cellular composition in patients developing BOS, or not, by analyzing peripheral blood taken at multiple time points after transplantation. PBMCs of 11 BOS and 39 non-BOS patients were analyzed by FACS for monocytes, dendritic cells, NK-, NKT-, B- and T cells as well as B- and T cell subsets.