Immunoglobulin G Subclasses Research Articles

Phase 1 study of LY3022855, a colony-stimulating factor-1 receptor (CSF-1R) inhibitor, in patients with metastatic breast cancer (MBC) or metastatic castration-resistant prostate cancer (MCRPC).

2548 Background: Tumor-associated macrophages (TAM) correlate with increased invasiveness, growth, and immunosuppression. Activation of CSF-1R results in proliferation, differentiation, and migration of monocytes/macrophages. CSF-1R inhibition with LY3022855 (LY), a human immunoglobulin G subclass 1 (IgG1) monoclonal antibody (mAB), may have favorable anti-tumor effects. We evaluated the safety and clinical response of LY monotherapy. Methods: Patients (pts) with advanced refractory MBC and MCRPC received LY intravenously in 6-week cycles in cohorts: A) 1.25 mg/kg every 2 weeks [Q2W]; B) 1.0 mg/kg on Weeks 1, 2, 4, and 5; C) 100 mg once weekly; D)100 mg Q2W. MCRPC pts were enrolled in cohorts A and B; MBC pts were enrolled in all cohorts. Anti-tumor activity was assessed using RECIST v1.1 by radiological imaging every 6 weeks. Results: Thirty-four pts (22 MBC; 12 MCRPC) received ≥1 dose of LY. Median age was 57.0 years (range: 32.0–81.0) for MBC pts and 72.5 years (range: 58.0–84.0) for MCRPC pts. Baseline Eastern Cooperative Oncology Group performance status was 0 (n = 13, 38.2%), 1 (n = 18, 52.9%), or 2 (n = 3, 8.8%). MBC pts were hormone receptor (HR) positive (n = 20), HR negative (n = 1), or unknown (n = 1); 3 MBC pts received concurrent hormone therapy. Common treatment-related adverse events of any grade were fatigue (38.2%), decreased appetite (26.5%), nausea (26.5%), increased lipase (23.5%), and increased creatine phosphokinase (20.6%). No complete or partial response was observed. Stable disease (SD) was observed in 5/22 MBC pts (duration 82–302 days) and 3/7 evaluable MCPRC pts (duration 50–124 days). Two MBC pts (9%; Cohort A) had durable SD > 9 months and 1 pt had palpable reduction in a nontarget neck mass. Circulating CSF1 and IL-34 increased at Day 8 suggestive of target engagement. Pharmacokinetics of LY were consistent with other IgG1 mAbs. Conclusions: LY3022855 was well tolerated and showed evidence of target engagement. Clinically meaningful SD > 9 months was observed in 2 MBC pts. Tumor biomarker analyses are underway. Clinical trial information: NCT02265536.

Contribution of Functional Antimalarial Immunity to Measures of Parasite Clearance in Therapeutic Efficacy Studies of Artemisinin Derivatives.

BackgroundAntibodies to the blood stages of malaria parasites enhance parasite clearance and antimalarial efficacy. The antibody subclass and functions that contribute to parasite clearance during antimalarial treatment and their relationship to malaria transmission intensity have not been characterized.MethodsLevels of immunoglobulin G (IgG) subclasses and C1q fixation in response to Plasmodium falciparum merozoite antigens (erythrocyte-binding antigen [EBA] 175RIII-V, merozoite surface protein 2 [MSP-2], and MSP-142) and opsonic phagocytosis of merozoites were measured in a multinational trial assessing the efficacy of artesunate therapy across 11 Southeast Asian sites. Regression analyses assessed the effects of antibody seropositivity on the parasite clearance half-life (PC½), having a PC½ of ≥5 hours, and having parasitemia 3 days after treatment.ResultsIgG3, followed by IgG1, was the predominant IgG subclass detected (seroprevalence range, 5%–35% for IgG1 and 27%–41% for IgG3), varied across study sites, and was lowest in study sites with the lowest transmission intensity and slowest mean PC½. IgG3, C1q fixation, and opsonic-phagocytosis seropositivity were associated with a faster PC½ (range of the mean reduction in PC½, 0.47–1.16 hours; P range, .001–.03) and a reduced odds of having a PC½ of ≥5 hours and having parasitemia 3 days after treatment.ConclusionsThe prevalence of IgG3, complement-fixing antibodies, and merozoite phagocytosis vary according to transmission intensity, are associated with faster parasite clearance, and may be sensitive surrogates of an augmented clearance capacity of infected erythrocytes. Determining the functional immune mechanisms associated with parasite clearance will improve characterization of artemisinin resistance.

Anti-donor immunoglobulin G subclass in liver transplantation.

Immunoglobulin G (IgG) subclasses in human health and immunity have only be sporadically studied in the half century since their discovery. Different patterns of IgG subclass production are seen if the immune response is deviated towards type 1 versus type 2. The current state of our knowledge of IgG subclasses in liver transplantation is reviewed here. While several studies have been conducted in liver disease, only four relatively small studies have been undertaken in liver transplant recipients. Total IgG4 elevation in serum is related to sclerosing pancreatico-cholangiopathy that is sensitive to treatment with steroids. Conventional immunosuppressive regimes, especially with a combination of tacrolimus and sirolimus, reduce the production of all IgG subclasses after transplantation but it is not known if they deviate the immune response. Presence of anti-donor IgG3 before transplantation, or its expansion after transplantation, has been associated with rejection and liver graft loss. Anti-GSTT1 IgG4 production after transplantation is associated with de-novo immune hepatitis. Greater knowledge of anti-donor IgG subclass responses after transplantation will allow us tailor novel treatments for greater effect.

Multiple Variables at the Leukocyte Cell Surface Impact Fc γ Receptor-Dependent Mechanisms.

Fc γ receptors (FcγR) expressed on the surface of human leukocytes bind clusters of immunoglobulin G (IgG) to induce a variety of responses. Many therapeutic antibodies and vaccine-elicited antibodies prevent or treat infectious diseases, cancers and autoimmune disorders by binding FcγRs, thus there is a need to fully define the variables that impact antibody-induced mechanisms to properly evaluate candidate therapies and design new intervention strategies. A multitude of factors influence the IgG-FcγR interaction; one well-described factor is the differential affinity of the six distinct FcγRs for the four human IgG subclasses. However, there are several other recently described factors that may prove more relevant for disease treatment. This review covers recent reports of several aspects found at the leukocyte membrane or outside the cell that contribute to the cell-based response to antibody-coated targets. One major focus is recent reports covering post-translational modification of the FcγRs, including asparagine-linked glycosylation. This review also covers the organization of FcγRs at the cell surface, and properties of the immune complex. Recent technical advances provide high-resolution measurements of these often-overlooked variables in leukocyte function and immune system activation.

Comparative Analysis of Igg Responses to Recombinant Qβ Phage Displayed MSP3 and UB05 in Dual HIV-Malaria Infected Adults Living in areas differing in Malaria Transmission Intensities

Immunoglobulin G (IgG) specific responses against Plasmodium falciparum merozoite antigens such as the merozoite surface protein 3 (MSP3) and UB05 are known to play critical roles in parasiteamia control and protection from symptomatic illness. However when there is intense perennial malaria transmission coupled with concurrent infection with the human immunodeficiency virus type 1 (HIV), knowledge of IgG antibody response profiles is limited. In this study we assessed the impact of dual HIV-Malaria infections on IgG subclass responses to MSP3 (QβMSP3) and UB05 (QβUB05) in individuals living in two areas of Cameroon differing in malaria transmission intensity. We observed differences in antigen specific IgG and IgG subclass responses which were dependent upon the antigen type, malaria transmission intensity, HIV infection, malaria infection and dual HIV-malaria infections. Individuals living in high malaria transmission areas irrespective of HIV or malaria status had significantly higher IgG responses to both antigens (P=0.0001 for QβMSP3, P=0.0001 for QβUB05) than their counterpart from low transmission areas. When dual HIV-Malaria infection is considered significantly higher QβMSP3 specific IgG1 (P=0.0001) and IgG3 (P=0.04) responses in double negative individuals was associated with protection against malaria in low transmission areas. Increased QβUB05 specific IgG1 responses (P=0.0001) in double negative individuals were associated with protection in high transmission areas in contrast to significantly higher IgG3 responses to QβUB05 (P=0.0001) which were more relevant to protection in low malaria transmission areas in the same population. These findings imply that QβMSP3 might not be suitable as a standalone vaccine in areas differing in transmission intensity. However, antigenicity of UB05 most likely predicts immunity in both low and high transmission areas and could be used either alone or in combination with other antigens for vaccine studies in areas differing in transmission intensities. Understanding immune responses to QβUB05 and QβMSP3 could thus enable the development of efficacious vaccines or commensurate immunotherapeutic strategies suitable for areas differing in malaria transmission intensity.

Normal IgG Antibody Deficiency

Primary antibody deficiency is typically associated with decreased serum concentrations of immunoglobulin G (IgG) and variable changes in IgA and IgM concentrations. We report a 58-year-old male patient who was diagnosed with a primary antibody deficiency in 1993 after five hospital admissions with separate episodes of pneumonia in a 12 month period. Initial investigation determined IgG 10 g/L, IgA <2.0 g/L and IgM <2.0 g/L. IgG subclasses were normal. Bone marrow and peripheral blood B cells (CD19+ and CD20+) were absent and no immunoglobulin response was detected after vaccinations with conjugated Haemophilus B, unconjugated pneumovax 23 and tetanus toxoid. He commenced replacement immunoglobulin and remained well over 25 years until treatment was inadvertently ceased for a 9 month period, at which point he developed a life threatening pneumonia requiring admission to intensive care. The same pattern of immunoglobulin concentration was noted.

A toolbox of IgG subclass-switched recombinant monoclonal antibodies for enhanced multiplex immunolabeling of brain.

Generating recombinant monoclonal antibodies (R-mAbs) from mAb-producing hybridomas offers numerous advantages that increase the effectiveness, reproducibility, and transparent reporting of research. We report here the generation of a novel resource in the form of a library of recombinant R-mAbs validated for neuroscience research. We cloned immunoglobulin G (IgG) variable domains from cryopreserved hybridoma cells and input them into an integrated pipeline for expression and validation of functional R-mAbs. To improve efficiency over standard protocols, we eliminated aberrant Sp2/0-Ag14 hybridoma-derived variable light transcripts using restriction enzyme treatment. Further, we engineered a plasmid backbone that allows for switching of the IgG subclasses without altering target binding specificity to generate R-mAbs useful in simultaneous multiplex labeling experiments not previously possible. The method was also employed to rescue IgG variable sequences and generate functional R-mAbs from a non-viable cryopreserved hybridoma. All R-mAb sequences and plasmids will be archived and disseminated from open source suppliers.

Immunoglobulin G subclass and antibody avidity responses in Malian children immunized with Plasmodium falciparum apical membrane antigen 1 vaccine candidate FMP2.1/AS02A

BackgroundA malaria vaccine based on Plasmodium falciparum apical membrane antigen 1 (AMA1) elicited strain specific efficacy in Malian children that waned in the second season after vaccination despite sustained AMA1 antibody titers. With the goal of identifying a humoral correlate of vaccine-induced protection, pre- and post-vaccination sera from children vaccinated with the AMA1 vaccine and from a control group that received a rabies vaccine were tested for AMA1-specific immunoglobulin G (IgG) subclasses (IgG1, IgG2, IgG3, and IgG4) and for antibody avidity.MethodsSamples from a previously completed Phase 2 AMA1 vaccine trial in children residing in Mali, West Africa were used to determine AMA1-specific IgG subclass antibody titers and avidity by ELISA. Cox proportional hazards models were used to assess correlation between IgG subclass antibody titers and risk of time to first or only clinical malaria episode and risk of multiple episodes. Asexual P. falciparum parasite density measured for each child as area under the curve were used to assess correlation between IgG subclass antibody titers and parasite burden.ResultsAMA1 vaccination did not elicit a change in antibody avidity; however, AMA1 vaccinees had a robust IgG subclass response that persisted over the malaria transmission season. AMA1-specific IgG subclass responses were not associated with decreased risk of subsequent clinical malaria. For the AMA1 vaccine group, IgG3 levels at study day 90 correlated with high parasite burden during days 90–240. In the control group, AMA1-specific IgG subclass rise and persistence over the malaria season was modest and correlated with age. In the control group, titers of several IgG subclasses at days 90 and 240 correlated with parasite burden over the first 90 study days, and IgG3 at day 240 correlated with parasite burden during days 90–240.ConclusionsNeither IgG subclass nor avidity was associated with the modest, strain-specific efficacy elicited by this blood stage malaria vaccine. Although a correlate of protection was not identified, correlations between subclass titers and age, and correlations between IgG subclass titers and parasite burden, defined by area under the curve parasitaemia levels, were observed, which expand knowledge about IgG subclass responses. IgG3, known to have the shortest half-life of the IgG subclasses, might be the most temporally relevant indicator of ongoing malaria exposure when examining antibody responses to AMA1.

IgG4 subclass and gamma-glutamyl transferase in children with ulcerative colitis with primary sclerosing cholangitis and without sclerosing cholangitis.

Aim of the studyPrimary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease which could be associated with inflammatory bowel disease (IBD), particularly ulcerative colitis (UC). The aim of this study was to compare GGT and IgG4 levels among children with UC with PSC and without PSC.Material and methodsIn this cross sectional study children with UC with PSC and UC without PSC were included. Serum immunoglobulin G4 (IgG4) and gamma-glutamyl transpeptidase (GGT) levels of the 90 UC patients with and without concomitant PSC were measured. Children with serum IgG4 concentration > 175 mg/dl were considered to have elevated IgG4.ResultsElevated serum IgG4 was found in 8 of 30 (26.6%) patients with PSC vs. 3 of 60 (5.0%) patients without PSC. Compared with the group without symptoms of PSC, the group with PSC showed significantly higher levels of aspartate aminotransferases (AST; 22.5 U/l vs. 70.0 U/l, p < 0.001), alkaline phosphatase (ALP; 359.0 U/l vs. 602.0 U/l, p < 0.001), and IgG4 (56.0 vs. 73.0, p = 0.02). The odd ratio of the elevated IgG4 and GGT in predicting PSC was 6.9 (95% CI: 1.6-28.4) and 18 (95% CI: 5.7-55.9), respectively.ConclusionsAST, alanine aminotransferase (ALT), GGT, ALP, and serum IgG4 were significantly higher in UC patients with sclerosing cholangitis (SC) compared to UC patients without SC. GGT and IgG-4 measurements are recommended for evaluation of UC.

M281, an Anti-FcRn Antibody: Pharmacodynamics, Pharmacokinetics, and Safety Across the Full Range of IgG Reduction in a First-in-Human Study.

M281 is a fully human, anti‐neonatal Fc receptor (FcRn) antibody that inhibits FcRn‐mediated immunoglobulin G (IgG) recycling to decrease pathogenic IgG while preserving IgG production. A randomized, double‐blind, placebo‐controlled, first‐in‐human study with 50 normal healthy volunteers was designed to probe safety and the physiological maximum for reduction of IgG. Intravenous infusion of single ascending doses up to 60 mg/kg induced dose‐dependent serum IgG reductions, which were similar across all IgG subclasses. Multiple weekly doses of 15 or 30 mg/kg achieved mean IgG reductions of ≈85% from baseline and maintained IgG reductions ≥75% from baseline for up to 24 days. M281 was well tolerated, with no serious or severe adverse events (AEs), few moderate AEs, and a low incidence of infection‐related AEs similar to placebo treatment. The tolerability and consistency of M281 pharmacokinetics and pharmacodynamics support further evaluation of M281 in diseases mediated by pathogenic IgG.

IgG glycosylation in autoimmune diseases

Immunoglobulin G (IgG) is the most abundant glycoprotein in human serum. All IgG subclasses have a single-conserved N-linked glycosylation site at Asn297 of the heavy chain and 10–30% of IgGs are N-glycosylated also in a Fab region. N-glycans of Fc are sialylated and fucosylated biantennary complex-type structures. Glycosylation plays a key role in antibody function, and IgG N-glycans are essential for the proper activity of the immune system. Fc glycans are important for IgG effector functions, whereas Fab oligosaccharides modulate antigen binding. Glycosylation changes of IgG are associated with the development of various human diseases, including autoimmune states. The modification of one sugar moiety in N-glycan structure may result in the stimulation or suppression of immune response. The lack of core fucose leads to the enhancement of pro-inflammatory activity, whereas an increase of sialylation determines immunosuppressive properties of IgG. The contribution of IgG Fc glycosylation changes has been demonstrated in the pathogenesis of rheumatoid arthritis, lupus erythematosus and Crohn’s disease. A decrease in IgG galactosylation and sialylation, found in these diseases, activates effector cells and triggers inflammatory reactions. A detailed analysis of changes in IgG glycosylation and their effects on the development of autoimmune diseases is important in the treatment of these diseases. IgGs with modified α2,6-sialylation are used as therapeutic antibodies with anti-inflammatory properties. Numerous studies on IgG glycosylation have provided evidence of the role of this post-translational modification in the proper functioning of antibodies and the importance of changes in the structure of IgG glycans, mainly incomplete galactosylation and desialylation, in the pathogenesis of many diseases. The continuation of these studies may contribute to explaining the mechanisms of autoimmunity that is still poorly understood.

Immunological features and functional analysis of anti-CFH autoantibodies in patients with atypical hemolytic uremic syndrome.

Atypical hemolytic uremic syndrome (aHUS) is associated with defective complement regulation. Anti-complement factor H (CFH) antibodies were thought to participate in the pathogenesis of aHUS. The aim of this study was to address the functions and properties of CFH autoantibodies in a Chinese Han cohort of aHUS patients. Thirty-six anti-CFH antibody-positive aHUS patients at the acute phase of the disease were involved in this study. Clinical data of the patients were collected. Anti-CFH immunoglobulin G (IgG) subclasses and antibody isotypes were detected by ELISA. Epitope mapping was performed using recombinant CFH fragments (SCRs 1-4, SCR 7, SCRs 11-14, and SCRs 19-20). Purified IgG from plasma from seven patients were used for functional analyses. All patients presented with the classic triad of HUS. The anti-CFH autoantibodies mostly bound to the SCRs 19-20 domains of CFH but not the SCRs 1-4 domains. CFI cofactor activity was not disturbed by the anti-CFH antibody in any of the seven patients. Purified IgG interfered with the binding of CFH to C3b and CFH-mediated sheep erythrocyte protection in all seven patients. IgG from 4/5 (80%) patients tested inhibited the binding of CFH to glomerular endothelial cells. Our study suggests that the properties of CFH antibodies from patients with aHUS, including the recognition of SCRs and IgG subclasses, can influence and impair the biological role of CFH and therefore contribute to aHUS susceptibility.

Anti-HLA Donor-Specific IgG Subclasses and C1q-binding Evolution in Posttransplant Monitoring.

BackgroundThe identification of low-level antibodies by single-antigen bead methodology has brought advancements to risk evaluation of kidney transplant recipients. However, the use of mean fluorescence intensity (MFI) to quantify antibodies and to guide therapy is not enough. Notably, immunoglobulin G (IgG) subclass switching is hypothesized to follow a programmed sequence after an emergency signal from the germinal center. In transplantation this process is not clear yet. In the present study, we sequentially evaluate anti-HLA donor specific antibody (DSA) subclasses, their profile changes, and C1q-binding ability and the influence of those characteristics on antibody mediated rejection (AMR) occurrence and allograft function.MethodsA total of 30 DSA-positive patients were tested for IgG subclass content and C1q-binding in sequential serum samples.ResultsTwenty-one patients were DSA-positive before transplant; patients sensitized only by transfusion or pregnancies had IgG1 and/or IgG3, and patients sensitized by both transfusion and pregnancies or previous transplant showed a broader range of IgG subclasses. C1q binding was detected in high MFI made up of IgG1 or multiple IgG subclasses. Only 4 patients were positive for C1q posttransplantation and 3 of these showed an increase in MFI, changes in subclasses patterns, AMR, and allograft dysfunction.ConclusionsPosttransplant evaluation of DSA subclasses and the ability to bind C1q may be informative for both AMR occurrence and allograft dysfunction. Monitoring these events may help to better define risk and interventional time points.

Monoclonal immunoglobulin G deposits on tubular basement membrane in renal allograft: is this significant for chronic allograft injury?

BackgroundTubular basement membrane immune deposits (TBMID) has rarely been observed in renal allografts. It is usually found in BK virus nephropathy and immune complex glomerulonephritis; however, its significance is not well understood. We conducted a retrospective clinicopathological study on monoclonal immunoglobulin G (IgG) TBMID.MethodsWe studied 7177 renal allograft biopsy specimens obtained from Tokyo Women’s Medical University from 2007 to 2015 and performed light microscopic, electron microscopic and immunofluorescence studies.ResultsTubular basement membrane (TBM) deposits of IgG were found in 73 biopsies from 61 patients and the IgG subclass was obtained in 31 biopsies. There were no cases of monoclonal IgA or IgM TBMID. In total, 13 biopsies from 10 patients showed monoclonal IgG TBMID. Of these, seven showed monoclonal IgG1κ TBMID and one each showed monoclonal IgG2κ, IgG2λ and IgG3κ TBMID. Conversely, eight patients showed polyclonal IgG TBMID. In electron microscopy, large granular electron-dense deposits (EDDs) in the TBM were detected in all patients with monoclonal IgG1κ TBMID. EDDs were absent in TBM in patients with monoclonal IgG2κ, IgG2λ or IgG3κ TBMID. Progression of interstitial fibrosis and tubular atrophy (IFTA) was significantly higher in patients with monoclonal IgG1κ TBMID than in those with polyclonal IgG TBMID (P < 0.05). There were no significant differences in the other clinical parameters between monoclonal IgG1κ and polyclonal IgG TBMID.ConclusionsThis is the first study of patients with monoclonal IgG TBMID in renal allografts. We found that monoclonal IgG1κ TBMID was associated with EDD formation in TBM and IFTA progression.

Analysis of intracellular IgG secretion in Chinese hamster ovary cells to improve IgG production

The production of biopharmaceutical immunoglobulin G (IgG) using cultured mammalian cells, especially Chinese hamster ovary (CHO) cells is well established and has been markedly improved through the modification of cells and cell culture engineering technologies. The establishment of high-production cell lines remains a challenge. The intracellular secretion of IgG has been investigated to identify and solve the rate-limiting steps in antibody production. However, strategies that regulate the expression of proteins that are related to antibody secretory pathway have not consistently improved their production. In this study, key features and limitations of the antibody secretion process in recombinant CHO cells were analyzed to develop more efficient approaches for establishing high-production cells. By chase assay with protein translation inhibitors, IgG secretion reached a plateau when at least 20% of IgG remained in the cells. The secretion kinetics and retention ratio of IgG varied between IgG subclasses (two types of IgG1 and an IgG3 subclass). Immunofluorescent microscopy and size exclusion chromatography showed that the remaining intracellular IgG localized mainly within the endoplasmic reticulum (ER) and less with the cis-Golgi network, despite the formation of fully assembled IgG. These results show that remaining intracellular IgG is a target for enhancing antibody secretion, even in high-production CHO cells.

Distribution of Anti-ABO Immunoglobulin G Subclass and C1q Antibody in ABO Incompatible Kidney Transplantation

Introduction To investigate the correlation between serum anti-ABO immunoglobulin G (IgG) and IgG subtypes, anti-ABO IgG subclasses were measured by flow cytometry (FCM) in ABO-incompatible (ABO-i) kidney transplant recipients (KTRs). We also evaluated baseline anti-ABO C1q antibody of KTRs. Method Baseline anti-ABO IgG titers were measured with both FCM and column agglutination technique (CAT) methods in 18 ABO-i KTRs. The mean florescence intensity (MFI) ratios of baseline Anti-ABO IgG subclasses were obtained by FCM method and followed up after rituximab (RTX), each plasmapheresis (PP) session and kidney transplantation. Correlation between the values of IgG subclass and total IgG titer were analyzed. Baseline anti-ABO C1q antibody was measured by FCM methods. Result The baseline MFI ratios of total IgG, IgG1, IgG2, IgG3 and IgG4 were 202.46, 62.41, 30.01, 1.04 and 1.13, respectively. The MFI ratios of IgG1, IgG2, and total IgG measured at baseline and pre-PP were positively correlated with the baseline ABO titer measured by CAT (rho, baseline; 0.641, 0.638, 0.663, PP; 0.662, 0.581, 0.662). However, Spearman correlation analysis revealed that baseline ABO titer did not show any correlation with the values after final PP and transplantation. IgG1 and IgG2 as well as total IgG were removed effectively after serial PP. However, anti-ABO C1q antibody was not detected and neither correlated with total IgG and any IgG subclasses. Conclusion Our findings suggest that IgG1 and IgG2 are dominant IgG subtypes in ABO-i KTRs. The mean baseline levels of IgG1 and IgG2 were correlated with baseline total IgG titer. However, anti-ABO C1q antibody was not detected in the present study. Further study is warranted to evaluate the function of each IgG subtype to activate complement pathway.

Clinicopathological study of de novo membranous nephropathy of ‘stage 0’ after kidney transplantation

De novo membranous nephropathy (dnMN) contributes to graft failure, but the pathophysiology of the disease remains poorly understood. We defined cases exhibiting granular Immunoglobulin G (IgG) immunofluorescence staining but lacking dense deposits on electron microscopy as being of 'dnMN stage 0'; we studied the associated clinicopathological features. We studied 4653 allograft biopsy specimens (from 1747 cases treated in the Department of Urology, Tokyo Women's Medical University) and found 42 cases of allograft membranous nephropathy, of which 28 (1.6%) were diagnosed as dnMN. Of these, five cases (0.06%) fulfilled the criteria for dnMN stage 0. All five cases were diagnosed based on biopsies indicating increased serum levels of creatinine. Proteinuria status varied from negative to 2+. The median period from transplantation to allograft biopsy was 4068 days. Four of the five cases exhibited suspicious antibody-mediated rejection together with dnMN. The glomerular capillaries of all cases were C4d-positive, as were the peritubular capillaries of three of the four ABO-compatible transplants. In terms of IgG subclass, IgG1 and IgG3 predominated in all cases, and phospholipase A2 receptor status (evaluated via immunoreactivity) was negative in all cases. We examined two cases by immunoelectron microscopy using anti-IgG and anti-C4d antibodies. We found subendothelial and intramembranous deposits expressing both IgG and C4d, corresponding to positivity in immunofluorescence analysis. We confirmed the existence of dnMN stage 0 by focusing on granular IgG immunofluorescence positivity.

Cytophilic Antibodies Against Key Plasmodium falciparum Blood Stage Antigens Contribute to Protection Against Clinical Malaria in a High Transmission Region of Eastern India.

The collection of clinical data from a tribal population in a malaria-endemic area of India suggests the occurrence of naturally acquired immunity (NAI) against Plasmodium falciparum malaria. Quantity and functionality of immunoglobulin G (IgG) antibodies against intact merozoites and recombinant proteins were assessed in a 13-month longitudinal cohort study of 121 individuals, 3-60 years of age. Opsonic phagocytosis of merozoites activity was strongly associated (hazard ratio [HR] = 0.34; 95% confidence interval [CI] = .18-.66; P = .0013) with protection against febrile malaria. Of the different IgG subclasses, only IgG3 antibodies against intact whole merozoites was significantly associated with protection against febrile malaria (HR = 0.47; 95% CI = .26-.86; P = .01). Furthermore, a combination of IgG3 antibody responses against Pf12, MSP3.7, MSP3.3, and MSP2FC27 was strongly associated with protection against febrile malaria (HR = 0.15; 95% CI, .06-.37; P = .0001). These data suggest that NAI may, at least in part, be explained by opsonic phagocytosis of merozoites and IgG3 responses against whole merozoites, and in particular to a combination of 4 antigens is critical in this population. These results may have implications in the development of a subunit malaria vaccine. Opsonic phagocytosis of Plasmodium falciparum merozoites was associated with protection against clinical malaria in an India population. Antibody profiling identified four merozoite antigens (Pf12, MSP3.7, MSP3.3, and MSP2) as targets of protective Immunoglobuline G3 antibodies.

Distribution of Anti-ABO Immunoglobulin G Subclass and C1q Antibody in ABO-incompatible Kidney Transplantation

IntroductionTo investigate the correlation between serum anti-ABO immunoglobulin G (IgG) and IgG subclasses, anti-ABO IgG subclasses were measured by flow cytometry (FCM) in ABO-incompatible (ABOi) kidney transplant recipients. We also evaluated baseline anti-ABO C1q antibody. MethodBaseline anti-ABO IgG titers were measured by both FCM and column agglutination technique methods in 18 ABOi kidney transplant recipients. The mean florescence intensity (MFI) ratios of baseline anti-ABO IgG subclasses and anti-ABO C1q antibody were obtained by FCM and followed-up after rituximab treatment, each plasmapheresis (PP) session, and kidney transplantation. Correlation between the values of IgG subclass and total IgG titer was analyzed. ResultsThe baseline MFI ratios of total IgG, IgG1, IgG2, IgG3, and IgG4 were 202.46, 62.41, 30.01, 1.04, and 1.13, respectively. The MFI ratios of IgG1, IgG2, and total IgG measured at baseline and pre-PP were positively correlated with the baseline ABO titer was measured using the column agglutination technique. The numbers of PP sessions to reach the target titer were correlated with the baseline IgG and IgG1 levels. IgG1 and IgG2 as well as total IgG were removed effectively after serial PP. Anti-ABO C1q antibody was neither detected nor correlated with total IgG and any IgG subclasses. ConclusionsOur findings suggest that IgG1 and IgG2 are the dominant IgG subclass in ABOi kidney transplant recipients. Baseline levels of IgG1 and IgG2 were correlated with baseline total IgG titer. However, anti-ABO C1q antibody was not detected in the present study.

Encephalitis with mGluR5 antibodies: Symptoms and antibody effects.

To report the clinical features of 11 patients with metabotropic glutamate receptor 5 (mGluR5) antibody-associated encephalitis, immunoglobulin G (IgG) subclass, and effects of the antibodies on neuronal mGluR5 clusters. Clinical information was retrospectively obtained from referring physicians. Antibodies to mGluR5 and IgG subclasses were determined with brain immunohistochemistry and cell-based assays. The effects of the antibodies were examined on rat hippocampal neurons with reported techniques. From January 2005 to May 2017, 11 patients (median age 29 years, range 6-75 years, 5 female) were identified. The main clinical features were psychiatric (10), cognitive (10), movement disorders (7), sleep dysfunction (7), and seizures (6). Median modified Rankin Scale score at the peak of the disease was 4; 4 patients required intensive care. Five patients had Hodgkin lymphoma, and 1 had small cell lung cancer. CSF showed pleocytosis (median white blood cell count 22 mm3) in all patients; brain MRI was abnormal in 5, involving limbic (1) or extralimbic (4) regions. Treatments included immunotherapy and/or oncologic therapy; at the last follow-up (median 48 months), 6 patients had complete and 5 had partial recovery. Neurologic relapse occurred in 2 patients. Antibodies were IgG1 alone (4 of 9) or in combination with IgG2 (1 of 9), IgG3 (3 of 9), or both (1). Patients' IgG caused a significant and specific decrease of cell-surface synaptic and extrasynaptic mGluR5 without altering the levels of postsynaptic density protein 95. Anti-mGluR5 encephalitis associates with a complex neuropsychiatric syndrome, not restricted to limbic encephalitis, and can occur without tumor. Patients respond to treatment, but relapses can occur. The antibodies have pathogenic effects altering the levels of cell-surface mGluR5.