IgG Subclass Distribution Research Articles

Cellular and humoral immunity and IgG subclass distribution after omicron XBB.1.5 monovalent vaccination in Japan

BackgroundUp to seven doses of coronavirus disease 2019 (COVID-19) mRNA vaccines (BNT162b2) were administered to Japanese healthcare workers, until February 2024. The monovalent Omicron XBB.1.5 vaccine (hereafter called XBB.1.5 vaccine) was used for dose 7. ObjectiveAlthough the XBB.1.5 vaccine has been reported to induce a robust increase in neutralizing antibodies against the currently circulating Omicron variant BA.2.86, little is known about its serological effects in Japan, where the BNT162b2 mRNA vaccine is the most frequently administered in the world. Study designTwenty-five recipients of the XBB.1.5 vaccine, categorized as seronegative (n = 18) or seropositive (n = 7) based on their recent history of COVID-19, were analyzed. Neutralizing antibody titers against Omicron subvariants, receptor binding domain (RBD) IgG levels, IgG subclass distribution, and T-cell responses were assessed. ResultsWe found a significant increase in neutralizing antibody titers against XBB.1.5 and BA.2.86 variants following XBB.1.5 vaccination, particularly in seropositive individuals. No significant change in total RBD IgG levels was observed, indicating efficient induction of antibodies targeting regions outside the RBD by XBB.1.5 vaccination. IgG subclass analysis demonstrated no significant subclass switching after vaccination. T-cell responses against the virus were comparable between seropositive and seronegative groups. ConclusionsThe study suggests that XBB.1.5 vaccination enhances humoral immunity against Omicron variants without significant IgG subclass switching. However, some individuals with low pre-vaccination IgG titers did not exhibit increased antibody levels post-vaccination, raising concerns about potential immune tolerance.

Analysis of IgG subclass staining for IgG immunofluorescence-positive IgAnephropathy.

The clinicopathological significance of IgG subclass staining is unclear in IgG immunofluorescence (IF)-positive IgA nephropathy (IgAN). This study investigated IgG subclass distribution in IgG IF-positive IgAN by IF staining and examined their clinicopathological significance. From January 2015 to December 2020, 27 biopsies from 26 patients with IgG IF-positive IgAN who were IF-positive for any IgG subclass staining were collected. We compared the clinicopathological findings between cases with and without IF positivity for each IgG subclass. Of the 27 biopsies with IgG IF-positive IgAN, 20 (74.1%) were IF-positive for IgG1, 10 (37.0%) were positive for IgG2, 7 (25.9%) were positive for IgG3, and none were positive for IgG4. Oxford E and C scores were significantly higher in cases of IgG IF-positive IgAN than IgG IF-negative IgAN. The age at biopsy had a negative correlation with IgG1 IF intensity (γ=-0.604, p=0.001). The levels of proteinuria and microscopic hematuria as well as Oxford classification score were not significantly different between cases with or without positive staining for each IgG subclass. IgG IF intensity had a positive correlation with IgG1 IF intensity (γ=0.741, p<0.001). IgG1-positive IF staining intensity was highest among each IgG subclass in IgG IF-positive IgAN biopsies. A negative correlation was revealed between the age at biopsy and IgG1 IF intensity. Oxford E and C scores were higher in patients with IgG IF-positive IgAN than in those with IgG IF-negative IgAN. The Oxford score was not significantly different between the IgG subclasses, but the IF intensity of IgG had a positive correlation with the IF intensity of IgG1 in IgG IF-positive IgAN biopsies. Further studies should assess relationships between IgG subclass IF deposition and examine the pathogenesis of IgAN.

Using imlifidase to elucidate the characteristics and importance of anti-GBM antibodies produced after start of treatment.

Autoantibodies are common in glomerulonephritis, but the clinical benefit of rapid elimination has not been determined, even in anti-glomerular basement membrane (GBM) disease. Even less is known about the importance of autoantibody characteristics, including epitope specificity and immunoglobulin G (IgG) subclass distribution. We aimed to address this by characterizing the autoantibody profile in anti-GBM patients: we utilized samples from the GOOD-IDES-01 (treating GOODpasture's disease with Imunoglobulin G Degrading Enzyme of Streptococcus pyogenous) (ClinicalTrials.gov identifier: NCT03157037) trial , where imlifidase, which cleaves all IgG in vivo within hours, was given to 15 anti-GBM patients. In the GOOD-IDES-01 trial, plasmapheresis was (re)started if anti-GBM antibodies rebounded. Serum samples were collected prospectively for 6months and analyzed for anti-GBM epitope specificity using recombinant constructs of the EA and EB epitopes, IgG subclass using monoclonal antibodies, and anti-neutrophil cytoplasmic antibodies (ANCA). The results were correlated with clinical data. Patients with a rebound (n=10) tended to have lower eGFR at 6months (11 vs 34mL/min/1.73 m2, P=.055), and patients with dialysis at 6months had a higher EB/EA ratio at rebound (0.8vs 0.5, P=.047). Moreover, two patients demonstrated increasing epitope restriction and several patients displayed a shift in subclass distribution at rebound. Six patients were double positive for ANCA. ANCA rebound was seen in 50% of patients; only one patient remained ANCA positive at 6 months. In this study, rebound of anti-GBM antibodies, especially if directed against the EB epitope, was associated with a worse outcome. This supports the notion that all means should be used to eliminate anti-GBM antibodies. In this study ANCA was removed early and long-term by imlifidase and cyclophosphamide.

The Impact of Pathogen Reduction on Total IgG and IgG Subclass Profiles of Convalescent Plasma

Introduction: In case of newly emerging pathogens, convalescent plasma (CP) is often the only early available treatment option. It has been shown that different IgG subclasses contribute differently to CP neutralizing activity. As CP donors often have a risk profile like first-time donors, especially with respect to window-period viral transmission, pathogen reduction (PR) could mitigate that risk. The aim of our study, especially in the light of potential future pandemics, was to evaluate the impact of commercially available PR technologies on total IgG and IgG subclasses quantity and distribution in CP using COVID-19 CP (CCP) as surrogate for CP in a side-by-side comparison approach. Methods: 36 apheresis CCP donations were allocated to three study groups and a side-by-side assessment of the potential impact of amotosalen (AS)/UVA treatment compared to a riboflavin (RB)/UVB treatment, AS against methylene blue (MB) treatment, and RB against MB treatment on the quantity of IgG and IgG subclasses with a nephelometric analyzer was performed. Results: IgG subclass distributions were not significantly changed post PR treatment with all three technologies. There was also no significant difference in the median loss of concentration for IgG1 and IgG2 between the three technologies. We recognized a non-significant trend of a higher IgG4 median loss post RB treatment compared to post AS and MB treatment, respectively. Conclusion: Although the three commercially available PR systems do not significantly alter the distribution of IgG subclasses, we detected a non-significant trend of higher IgG4 loss after RB treatment. The potential impact of that finding needs further investigation.

Analysis of the IgG subclass profile and IgG sum-total discrepancy in COVID-19 convalescent plasma donors: A single-centre prospective cohort study

IntroductionAlthough IgG1 and IgG3 have been shown to be the dominant subclasses in the acute phase of SARS-CoV-2 infection, little is known about the distribution of IgG subclasses during the recovery phase of COVID-19. The aim of the study was to analyze the profile of IgG subclasses in COVID-19 convalescent plasma donors. MethodsA total of 36 convalescent plasma donors were included in the analysis. IgG and IgG subclass levels were measured using a nephelometric assay in plasma samples obtained directly from the plasma container. ResultsAlthough there was no significant difference in the concentration of IgG subclasses between the study and control groups, the contribution of IgG1 to the total IgG pool between the study and control groups was statistically significant (p = 0.0478). In addition, there was a discrepancy between the total IgG and IgG sum values in the study group, exceeding 15 % in 19,4 % of samples (n = 7), while in the control group no samples with a sum/ total IgG difference > 15 % were observed. ConclusionsThe selective affinity of the IgG1 subclass for the polyclonal anti-IgG reagent may interfere with the determination of total IgG and should be considered when interpreting the results of enzyme immunoassays Data AvailabilityThe data that support the findings of this study are available on request from the corresponding author.

Type I Interferons Promote Germinal Centers Through B Cell Intrinsic Signaling and Dendritic Cell Dependent Th1 and Tfh Cell Lineages.

Type I interferons (IFNs) are essential for antiviral immunity, appear to represent a key component of mRNA vaccine-adjuvanticity, and correlate with severity of systemic autoimmune disease. Relevant to all, type I IFNs can enhance germinal center (GC) B cell responses but underlying signaling pathways are incompletely understood. Here, we demonstrate that a succinct type I IFN response promotes GC formation and associated IgG subclass distribution primarily through signaling in cDCs and B cells. Type I IFN signaling in cDCs, distinct from cDC1, stimulates development of separable Tfh and Th1 cell subsets. However, Th cell-derived IFN-γ induces T-bet expression and IgG2c isotype switching in B cells prior to this bifurcation and has no evident effects once GCs and bona fide Tfh cells developed. This pathway acts in synergy with early B cell-intrinsic type I IFN signaling, which reinforces T-bet expression in B cells and leads to a selective amplification of the IgG2c+ GC B cell response. Despite the strong Th1 polarizing effect of type I IFNs, the Tfh cell subset develops into IL-4 producing cells that control the overall magnitude of the GCs and promote generation of IgG1+ GC B cells. Thus, type I IFNs act on B cells and cDCs to drive GC formation and to coordinate IgG subclass distribution through divergent Th1 and Tfh cell-dependent pathways.

The Diversity of Serum Anti-DSG3 IgG Subclasses Has a Major Impact on Pemphigus Activity and Is Predictive of Relapses After Treatment With Rituximab.

IntroductionWe studied the distribution and in vitro pathogenicity of anti-DSG3 IgG subclasses during the course of pemphigus vulgaris (PV).MethodsWe longitudinally studied the distribution of anti-DSG3 IgG subclasses (before versus after treatment) in sera from PV patients, using an addressable-laser bead immunoassay (ALBIA). The in vitro pathogenicity of corresponding sera was tested using keratinocyte dissociation and immunofluorescence assays.ResultsSixty-five sera were assessed at baseline (33 from patients treated with rituximab and 32 with corticosteroids). Sixty-three percent of these baseline sera contained 2 or more anti-DSG3 IgG subclasses versus 35.7% of sera from patients in complete remission (CR) and 75.0% of sera from patients with persistent disease activity after treatment. IgG4 was the most frequently detected anti-DSG3 IgG subclass, both in patients with disease activity and in those in CR. The presence of three or more anti-DSG3 IgG subclasses was predictive of relapse, in particular when it included IgG3, with a positive predictive value of 62.5% and a negative predictive value of 92%. While anti-DSG3 IgG4 Abs from sera collected before treatment were most often pathogenic, anti-DSG3 IgG4 from sera collected after treatment were pathogenic only after adjusting their titer to the one measured before treatment. The IgG3 fraction containing anti-DSG3 Abs also had an in vitro pathogenic effect. The disappearance of the pathogenic effect of some sera after removal of anti-DSG3 IgG3 suggested an additional effect of this IgG subclass.ConclusionThe serum levels and number of anti-DSG3 IgG subclasses drive the pathogenic effect of pemphigus sera and may predict the occurrence of relapses.

Frequent Development of Broadly Neutralizing Antibodies in Early Life in a Large Cohort of Children With Human Immunodeficiency Virus.

Recent studies have indicated that broadly neutralizing antibodies (bnAbs) in children may develop earlier after human immunodeficiency virus (HIV) infection compared to adults. We evaluated plasma from 212 antiretroviral therapy-naive children with HIV (1-3 years old). Neutralization breadth and potency was assessed using a panel of 10 viruses and compared to adults with chronic HIV. The magnitude, epitope specificity, and immunoglobulin (Ig)G subclass distribution of Env-specific antibodies were assessed using a binding antibody multiplex assay. One-year-old children demonstrated neutralization breadth comparable to chronically infected adults, whereas 2- and 3-year-olds exhibited significantly greater neutralization breadth (P = .014). Likewise, binding antibody responses increased with age, with levels in 2- and 3-year-old children comparable to adults. Overall, there was no significant difference in antibody specificities or IgG subclass distribution between the pediatric and adult cohorts. It is interesting to note that the neutralization activity was mapped to a single epitope (CD4 binding site, V2 or V3 glycans) in only 5 of 38 pediatric broadly neutralizing samples, which suggests that most children may develop a polyclonal neutralization response. These results contribute to a growing body of evidence suggesting that initiating HIV immunization early in life may present advantages for the development of broadly neutralizing antibody responses.

SARS-CoV-2 Antibodies Mediate Complement and Cellular Driven Inflammation.

The ongoing pandemic of coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to constitute a serious public health threat worldwide. Protective antibody-mediated viral neutralization in response to SARS-CoV-2 infection has been firmly characterized. Where the effects of the antibody response are generally considered to be beneficial, an important biological question regarding potential negative outcomes of a SARS-CoV-2 antibody response has yet to be answered. We determined the distribution of IgG subclasses and complement activation levels in plasma from convalescent individuals using in-house developed ELISAs. The IgG response towards SARS-CoV-2 receptor-binding domain (RBD) after natural infection appeared to be mainly driven by IgG1 and IgG3 subclasses, which are the main ligands for C1q mediated classical complement pathway activation. The deposition of the complement components C4b, C3bc, and TCC as a consequence of SARS-CoV-2 specific antibodies were depending primarily on the SARS-CoV-2 RBD and significantly correlated with both IgG levels and disease severity, indicating that individuals with high levels of IgG and/or severe disease, might have a more prominent complement activation during viral infection. Finally, freshly isolated monocytes and a monocyte cell line (THP-1) were used to address the cellular mediated inflammatory response as a consequence of Fc-gamma receptor engagement by SARS-CoV-2 specific antibodies. Monocytic Fc gamma receptor charging resulted in a significant rise in the secretion of the pro-inflammatory cytokine TNF-α. Our results indicate that SARS-CoV-2 antibodies might drive significant inflammatory responses through the classical complement pathway and via cellular immune-complex activation that could have negative consequences during COVID-19 disease. We found that increased classical complement activation was highly associated to COVID-19 disease severity. The combination of antibody-mediated complement activation and subsequent cellular priming could constitute a significant risk of exacerbating COVID-19 severity.

Cerebrospinal fluid and plasma distribution of anti-α-synuclein IgMs and IgGs in multiple system atrophy and Parkinson's disease

IntroductionUbiquitous naturally occurring autoantibodies (nAbs) against alpha-synuclein (α-syn) may play important roles in the pathogenesis of Multiple System Atrophy (MSA) and Parkinson's disease (PD). Recently, we reported reduced high-affinity/avidity anti-α-syn nAbs levels in plasma from MSA and PD patients, along with distinct inter-group immunoglobulin (Ig)G subclass distributions. The extent to which these observations in plasma may reflect corresponding levels in the cerebrospinal fluid (CSF) is unknown. MethodsUsing competitive and indirect ELISAs, we investigated the affinity/avidity of CSF anti-α-syn nAbs as well as the CSF and plasma distribution of IgG subclasses and IgM nAbs in a cross-sectional cohort of MSA and PD patients. ResultsRepertoires of high-affinity/avidity anti-α-syn IgG nAbs were reduced in CSF samples from MSA and PD patients compared to controls. Furthermore, anti-α-syn IgM nAb levels were relatively lower in CSF and plasma from MSA patients but were reduced only in plasma from PD patients. Interestingly, anti-α-syn IgG subclasses presented disease-specific profiles both in CSF and plasma. Anti-α-syn IgG1, IgG2 and IgG3 levels were relatively increased in CSF of MSA patients, whereas PD patients showed increased anti-α-syn IgG2 and reduced anti-α-syn IgG4 levels. ConclusionsDifferences in the plasma/CSF distribution of anti-α-syn nAbs seem to be a common feature of synucleinopathies. Our data add further support to the notion that MSA and PD patients may have compromised immune reactivity towards α-syn. The differing α-syn-specific systemic immunological responses may reflect their specific disease pathophysiologies. These results are encouraging for further investigation of these immunological mechanisms in neurodegenerative diseases.

Necrotizing Pancreatitis Secondary to Dulaglutide Use

Introduction/ Background: GLP-1 agonists are an essential component of the anti-diabetes armamentarium. Common side effects include mild gastrointestinal distress and headaches. Uncommon side effects include acute pancreatitis and can limit use. We report a case of acute severe necrotizing pancreatitis most likely attributed to dulaglutide.Clinical Case: A 69-year-old man presented lethargic with diffuse abdominal pain associated with nausea and vomiting of 1-day duration. His past medical history consisted of type 2 diabetes, hyperlipidemia, hypertension, and hypothyroidism. His diabetes regimen included metformin, glipizide, and empagliflozin. Dulaglutide was added three months prior at 0.75 mg weekly, and the dose was increased to 1.5 mg weekly three days before presentation, the patient having received one such dose. Initial workup showed lipase 2800 units/mL, amylase 1185 units/mL, lactate 12.6 mmol/L, white blood cells 20 x 109/L, glucose 348 mg/dL, AST 30 unit/L, hematocrit 51.5%, blood urea nitrogen 24 mg/dL, and serum creatinine 1.57 mg/dL, calcium 8.1 mg/dL. No stones or CBD dilation were noted on ultrasound. Initial CT showed an enlarged pancreas with peripancreatic stranding and slightly diminished enhancement consistent with early signs of necrotizing pancreatitis. The patient became increasingly hypoxic and hypotensive and required intubation and triple pressor support to maintain adequate perfusion. On the second day of hospitalization, his hematocrit was 35.7%, blood urea nitrogen 37 mg/dL, calcium 6.8 mg/dL, and bicarbonate 21 mmol/L. AST and ALT peaked at 209 and 398 unit/L respectively. Calculated 48 hours Ranson’s score was 7. He completed 7 days of meropenem for necrotizing pancreatitis. He developed cholecystitis secondary to inflammatory damage of the biliary tract and received a cholecystostomy tube. A follow-up CT scan 7 days after the initial scan showed a prominent pancreas with extensive inflammation and without cysts, with several areas of nonenhancement/poor perfusion in the pancreatic head consistent with pancreatic necrosis. The patient made a full recovery and was discharged to a rehabilitation unit. Investigation into other causes of pancreatitis revealed triglycerides 104 mg/dL, a normal distribution of IgG subclasses (IgG4 36 mg/dL), no significant alcohol use, and no family history of pancreatitis.Conclusion: Pancreatic safety studies of dulaglutide have shown a good safety profile1. However, FDA safety warning exists on GLP-1 agonist prescriptions. Necrotizing pancreatitis with GLP-1a is rarely reported. We present a case of severe necrotizing pancreatitis due to dulaglutide use with the existence of temporality, after ruling out other causes of pancreatitis.Reference: 1. Nauck MA et al. Assessment of Pancreas Safety in the Development Program of Once-Weekly GLP-1 Receptor Agonist Dulaglutide. Diabetes Care 2017;40:647–54.

Neurological disorders-associated anti-glycosphingolipid IgG-antibodies display differentially restricted IgG subclass distribution

Antibodies against several self-glycans on glycosphingolipids are frequently detected in different neurological disorders. Their pathogenic role is profusely documented, but the keys for their origin remain elusive. Additionally, antibodies recognizing non-self glycans appear in normal human serum during immune response to bacteria. Using HPTLC-immunostaining we aimed to characterize IgM and IgG subclass antibody responses against glycosphingolipids carrying self glycans (GM1/GM2/GM3/GD1a/GD1b/GD3/GT1b/GQ1b) and non-self glycans (Forssman/GA1/“A” blood group/Nt7) in sera from 27 randomly selected neurological disorder patients presenting IgG reactivity towards any of these antigens. Presence of IgG2 (p = 0.0001) and IgG1 (p = 0.0078) was more frequent for IgG antibodies against non-self glycans, along with less restricted antibody response (two or more simultaneous IgG subclasses). Contrariwise, IgG subclass distribution against self glycans showed clear dominance for IgG3 presence (p = 0.0017) and more restricted IgG-subclass distributions (i.e. a single IgG subclass, p = 0.0133). Interestingly, anti-self glycan IgG antibodies with simultaneous IgM presence had higher proportion of IgG2 (p = 0.0295). IgG subclass frequencies were skewed towards IgG1 (p = 0.0266) for “anti-self glycan A” subgroup (GM2/GM1/GD1b) and to IgG3 (p = 0.0007) for “anti-self glycan B” subgroup (GM3/GD1a/GD3/GT1b/GQ1b). Variations in players and/or antigenic presentation pathways supporting isotype (M-G) and IgG-subclass pattern differences in the humoral immune response against glycosphingolipids carrying non-self versus self-glycans are discussed.

Efficiency of placental transfer of vaccine-elicited antibodies relative to prenatal Tdap vaccination status

Administration of vaccines during pregnancy provides maternal protection against infectious diseases. This protection is extended to their infants during the first months of life, as pathogen-specific antibodies formed in response to maternal vaccination are transferred across the placenta to the fetus. Notably, Tdap (tetanus-diphtheria-acellular pertussis) vaccination booster is routinely administered to pregnant women both to prevent neonatal tetanus and to ensure that infants have protective levels of pertussis antibodies until they are able to establish their own vaccine-induced levels. Whether infant protection through maternal immunization is merely due to an increase in maternal antibody levels or whether maternal immunization enhances the transfer of vaccine-specific antibodies is unclear. Moreover, the potential impact of prenatal vaccinations on the transplacental transfer of other antibodies, such as antibodies raised as a result of infections or other vaccines administered prior to pregnancy, has not been studied.The goal of this study was to define the impact of maternal vaccination on IgG transplacental transfer efficiency. We analyzed antigen-specific antibody populations and IgG subclass distribution in maternal and cord blood samples from 58 mother-infant pairs. All women received the seasonal inactivated influenza vaccine during pregnancy and 25 women received the Tdap vaccine during the second or third trimester of gestation. Prenatal Tdap vaccination did not impact the efficiency of IgG transplacental transfer; however, it was associated with higher maternal and infant vaccine-elicited Tdap-specific antibody levels, and with a higher proportion of infants with protective levels of antibodies, especially against diphtheria. There was also no difference in the IgG transplacental transfer rate of antibodies against non-Tdap vaccines between the two groups of women. Our results confirm previous reports demonstrating the benefits of prenatal Tdap immunization and indicate that this strategy does not impede the transplacental transfer of other antibodies that are also important for infant protection.

The IgM and IgG subclass distribution of anti-Galactose-alpha-1,3-galactose and anti-N-glycolylneuraminic acid antibodies in healthy adults

Abstract Background The major xenoreactive antibodies (Abs), anti-galactose-alpha-1,3-galactose (Gal) and anti-N-glycolylneuraminic acid (Neu5Gc), exist naturally in humans and can contribute to several immunological pathogenesis in xenotransplantation. In this study, we investigated the serum titers of anti-Gal and anti-Neu5Gc Abs including the IgM, IgG, and IgG subclasses in humans to gather basic population data before launching clinical xenotransplantation. Methods Serum titers of anti-Gal and anti-Neu5Gc Abs were measured in 380 healthy adults using an in-house-developed enzyme-linked immunosorbent assay. The detection frequency and distribution of anti-Gal and anti-Neu5Gc IgM, IgG and IgG subclass were evaluated. Results The detection frequencies of Abs were as follows: for anti-Gal, IgG, 95.0%; IgM, 99.2%; IgG1, 23.2%; IgG2, 94.5%; IgG3, 12.4%; and IgG4, 3.4%, and for anti-Neu5Gc, IgG, 96.6%; IgM, 87.4%; IgG1, 1.6%; IgG2, 46.3%. The median titers of anti-Gal IgG (1,198 ng/ml, range &amp;lt;401 – 128,758 ng/ml) and IgM (996 ng/ml, range &amp;lt;113 – 24,698 ng/ml) were significantly higher than those of anti-Neu5Gc Abs (IgG, 194 ng/ml, range &amp;lt;30 – 12,415 ng/ml; IgM, 328 ng/ml, range &amp;lt;154 – 6,514 ng/ml; all P&amp;lt;0.001). IgG2 of both anti-Gal and anti-Neu5G Abs correlated better with the IgG class than other IgG subclasses (rs = 0.762, P &amp;lt; 0.001; rs = 0.606, P &amp;lt; 0.001). Conclusions Most healthy adults possess anti-Gal and anti-Neu5Gc IgG and IgM in their sera. Overall, the titers of anti-Gal Abs are higher than those of anti-Neu5Gc Abs. IgG2 seems to be the main IgG subclass in both anti-Gal and anti-Neu5Gc natural Abs. Changes in the titers of these Abs would be a clue to understand an immunological pathogenesis in the recipients of xenotransplantation.

Sentinel biomarkers in HCV positive patients with mixed cryoglobulinemia

BackgroundInfections, autoimmunity and cancer play a role as determinants of etiology in Hepatitis C virus (HCV) related mixed cryoglobulinemia (MC). Several factors of risk have been suggested as markers of pathogenesis and progression of HCV-related MC into B cell Non-Hodgkin's Lymphoma (B-NHL). Here, we evaluated IgG subclass distribution, free light chains (FLCs) and vascular endothelial growth factor (VEGF) as a new combination of biomarkers. MethodsWe measured IgG1–4 subclasses, FLCs and VEGF levels in sera 53 from HCV-related MC, in comparison with 40 sera from HCV negative patients with rheumatoid arthritis (RA) and 30 from healthy blood donors (HBD). ResultsIgG3 levels were significantly higher in HCV-MC patients with a decrement of IgG2 and IgG4; FLC levels significantly increased in both MC and RA patients' groups; serological VEGF was higher in HCV-MC patients than in HBD in correlation with k and λ levels. ConclusionOur results suggest that a specific IgG subclasses pattern together with raised levels of FLCs and VEGF could represent the biomarker “signature” of an inflammation multistage of acquired immune system.

Laboratory-immunological diagnostics of complicated flow of necrotic pancreatitis

Purpose of the study. Justify the additional laboratory and immunological possibilities of diagnosing the complications of necrotic pancreatitis.&#x0D; Materials and methods. A retrospective analysis of the case history of patients with edematous and necrotic pancreatitis has been carried out, and 1060 case histories have been analyzed. By special methods, 30 patients with acute pancreatitis were examined. Laboratory and immunological studies were carried out three times: 1 research – upon admission; 2 studies – on the 7th day; 3 studies – 14 days.&#x0D; Results. The conducted clinical researches and analysis of results allowed working out the method of diagnostics of local complications, based on quantitative estimation of level of lymphocytes. At level of lymphocytes up to 13% is very high probability of fluid collection development; from 13% to 25% high probability; from 25% to 37% – moderate probability; above 37% – low probability of intraand peripancreatic fluid collections. In general, a comparison of the dynamics of Ig subclasses showed that IgG1 and IgG3 tended to gradually increase.&#x0D; Conclusions. Among the laboratory parameters of the complicated course of necrotic pancreatitis, the most significant is the change in lymphocytes. The distribution of individual IgG subclasses suggests that severe necrotic forms overlap with a proven increase in the quantitative composition of IgG1 and IgG3, which is a confirmation of the pro inflammatory variant of the development of SIRS and requires correction of therapeutic tactics.

RECONSTITUTION OF IGG SUBCLASSES FOLLOWING IMMUNOGLOBULIN THERAPY IN ADULT PRIMARY HYPOGAMMAGLOBULINEMIA

Introduction A majority of patients receiving immunoglobulin (Ig) therapy respond with decreased frequency and severity of infections; however, a subset of patients does not respond adequately. This study aimed to determine [1] if failure to reconstitute subclass (es) is associated with inadequate clinical response, [2] whether reconstitution of subclasses differs among different routes of administration, and [3] which IgG subclasses contribute most to low total IgG. Methods Retrospective data from EMR and charts was collected for patients with primary hypogammaglobulinemia seen between 2010 and 2018. Data collected included serum IgG subclasses and frequency and type infections prior to and following immunoglobulin infusion via different routes of administration. Results Records were reviewed for 95 patients. All IgG subclasses were reconstituted in 82%. In 18% of patients IgG subclasses were not reconstituted and most commonly included IgG4 (50%) and IgG3 (30%). In the group in which subclasses did not reconstitute, infections included sinusitis, respiratory and urinary tract infections. Subclass reconstitution occurred in 88% on IVIG, 85% on conventional subcutaneous (SQ), and 100% on enzyme-facilitated SQ. The average number of annual infections was 0.74 with IVIG, 1.0 with conventional SQ and 0.67 with enzyme-facilitated SQ. At the time of diagnosis of hypogammaglobulinemia, distribution of low IgG subclasses was IgG1 (55%), IgG2 (38%), IgG3 (23%), and IgG4 (34%). Conclusions Failure to reconstitute IgG subclasses does not correlate with inadequate clinical response in hypogammaglobulinemia. Low levels of IgG1 and IgG2 contribute predominantly (83%) to hypogammaglobulinemia. Those on facilitated SQ therapy most frequently experienced subclass reconstitution.

Concept of sample-specific correction of immunoassay results for precise and accurate IgG quantification in horse plasma

The hyperimmune horse plasma (HHP), prepared through active immunisation of horses with an antigen of interest, is the most common starting material for antitoxin (animal antibody-based therapeutics) production. Precise IgG quantification in plasma is a prerequisite for accurate estimation of the purification process efficiency. Although immunoglobulins from HHP have been purified for over a century, there is still no in vitro method for precise and accurate determination of IgG content in HHP. For this reason, the purification process efficiency has been assessed by antibody activity measurements, mostly performed in vivo. Here we describe the development of a precise and accurate in vitro immunoassay for IgG quantification in HHP. We showed and highlighted that any difference in composition of IgG population between the standard and the sample, with respect to both IgG subclass distribution and antigen-specific IgG content, leads to inaccurate IgG quantification. We demonstrated that caprylic acid precipitation as the method for IgG isolation from horse plasma renders the composition of IgG population unchanged. This very efficient, fast, simple and inexpensive method was used to prepare internal, sample-specific reference IgG for each plasma sample, which was tested simultaneously to a respective plasma sample. Deviation of IgG quantity determined by ELISA for each sample-specific reference from its nominal value was used for correction of the results of respective plasma sample, which led to accurate and precise IgG quantification as shown by method validation. The here presented novel concept of sample-specific correction of immunoassay results could be widely applicable and easily introduced in different immunoassays for more accurate and precise plasma IgG quantification.

Antiphospholipid Antibodies to Domain I of Beta-2-Glycoprotein I Show Different Subclass Predominance in Comparison to Antibodies to Whole Beta-2-glycoprotein I.

Antiphospholipid antibodies (aPL), the serological hallmark of antiphospholipid syndrome (APS), are a heterogeneous group of autoantibodies raised against circulating blood proteins. Of these proteins, the phospholipid-binding b2-glycoprotein I (β2GPI) is considered to be the main autoantigen in APS. Indeed, IgG antibodies targeting b2GPI (ab2GPI) directly cause both thrombosis and pregnancy morbidity in several mouse models. While antibodies raised against all five domains of b2GPI have been reported, a subgroup of IgG ab2GPI raised against the first domain (DI) of b2GPI (aDI), strongly correlate with thrombotic APS, and drive thrombosis and pregnancy loss in vivo. Few studies have focused on determining the type of IgG subclass(es) for aPL. The subclass of an antibody is important as this dictates the potential activity of an antibody; for example, IgG1 and IgG3 can fix complement better and are able to cross the placenta compared to IgG2 and IgG4. It is unknown what subclass IgG aDI are, and whether they are the same as ab2GPI. To determine IgG subclass distribution for ab2GPI and aDI, we purified total IgG from the serum of 19 APS patients with known ab2GPI and aDI activity. Using subclass-specific conjugated antibodies, we modified our established in-house ab2GPI and aDI ELISAs to individually measure IgG1, IgG2, IgG3, and IgG4. We found that while IgG1, IgG2, and IgG3 ab2GPI levels were similar, a marked difference was seen in IgG subclass aDI levels. Specifically, significantly higher levels of IgG3 aDI were detected compared to IgG1, IgG2, or IgG4 (p < 0.05 for all comparisons). Correlation analysis of subclass-specific ab2GPI vs. aDI demonstrated that IgG3 showed the weakest correlation (r = 0.45, p = 0.0023) compared to IgG1 (r = 0.61, p = 0.0001) and IgG2 (r = 0.81, p = 0.0001). Importantly, total subclass levels in IgG purified from APS and healthy serum (n = 10 HC n = 12 APS) did not differ, suggesting that the increased IgG3 aDI signal seen in APS-derived IgG is antigen-specific. To conclude, our data suggests that aDI show a different IgG subclass distribution to ab2GPI. Our results highlight the importance of aDI testing for patient stratification and may point toward differential underlying aPL-driven pathogenic processes that may be subclass restricted.

Unidirectional transport of IgG by neonatal Fc receptor in human thyrocytes varies across different IgG subclasses.

Neonatal Fc receptor (FcRn) is down-regulated in Hashimoto's thyroiditis (HT) thyrocytes and mediates IgG endocytosis in thyrocytes. The serum distribution of IgG subclasses (of TgAb and TPOAb) differs between HT patients and normal individuals. We aimed to explore the direction and regulation of FcRn-mediated IgG transport in thyrocyte monolayers and the difference between various IgG subclass transport. IgG was transported by FcRn from the basolateral to apical side in the thyrocyte monolayers grown on Transwell filters and the transport was inhibited by IFN-γ and TNF-α. Stimulation by T3 and TSH down-regulated FcRn expression in thyrocytes. IgG1 was transported preferentially over IgG2 and IgG4, which might be related to the differences in FcRn-binding affinities as shown by SPR. FcRn mediates unidirectional IgG transport in thyrocytes in a tissue-specific manner. Down-regulation of FcRn is speculated to play a protective role in HT pathogenesis by mainly reducing IgG1 transport in thyrocytes.