Lower Immunoglobulin G Concentrations Research Articles

Effect of efgartigimod on muscle group subdomains in participants with generalized myasthenia gravis: post hoc analyses of the phase 3 pivotal ADAPT study.

Generalized myasthenia gravis (gMG) is a rare, chronic, neuromuscular autoimmune disease mediated by pathogenic immunoglobulin G (IgG) autoantibodies. Patients with gMG experience debilitating muscle weakness, resulting in impaired mobility, speech, swallowing, vision and respiratory function. Efgartigimod is a human IgG1 antibody Fc fragment engineered for increased binding affinity to neonatal Fc receptor. The neonatal Fc receptor blockade by efgartigimod competitively inhibits endogenous IgG binding, leading to decreased IgG recycling and increased degradation resulting in lower IgG concentration. The safety and efficacy of efgartigimod were evaluated in the ADAPT study. Key efficacy outcome measures included Myasthenia Gravis Activities of Daily Living (MG-ADL) and Quantitative Myasthenia Gravis (QMG) scores. Efgartigimod demonstrated significant improvement in both the MG-ADL and QMG scores. This post hoc analysis aimed to determine whether all subdomains of MG-ADL and QMG improved with efgartigimod treatment. Individual items of MG-ADL and QMG were grouped into four subdomains: bulbar, ocular, limb/gross motor and respiratory. Change from baseline over 10 weeks in each subdomain was calculated for each group. Greater improvements from baseline were seen across MG-ADL subdomains in participants treated with efgartigimod compared with placebo. These improvements were typically observed 1 to 2 weeks after the first infusion and correlated with reductions in IgG. Similar results were observed across most QMG subdomains. These post hoc analyses of MG-ADL and QMG subdomain data from ADAPT suggest that efgartigimod is beneficial in improving muscle function and strength across all muscle groups, leading to the observed efficacy in participants with gMG.

Oligoclonal Band Straightening Based on Optimized Hierarchical Warping for Multiple Sclerosis Diagnosis.

The detection of immunoglobulin G (IgG) oligoclonal bands (OCB) in cerebrospinal fluid (CSF) by isoelectric focusing (IEF) is a valuable tool for the diagnosis of multiple sclerosis. Over the last decade, the results of our clinical research have suggested that tears are a non-invasive alternative to CSF. However, since tear samples have a lower IgG concentration than CSF, a sensitive OCB detection is therefore required. We are developing the first automatic tool for IEF analysis, with a view to speeding up the current visual inspection method, removing user variability, reducing misinterpretation, and facilitating OCB quantification and follow-up studies. The removal of band distortion is a key image enhancement step in increasing the reliability of automatic OCB detection. Here, we describe a novel, fully automatic band-straightening algorithm. The algorithm is based on a correlation directional warping function, estimated using an energy minimization procedure. The approach was optimized via an innovative coupling of a hierarchy of image resolutions to a hierarchy of transformation, in which band misalignment is corrected at successively finer scales. The algorithm’s performance was assessed in terms of the bands’ standard deviation before and after straightening, using a synthetic dataset and a set of 200 lanes of CSF, tear, serum and control samples on which experts had manually delineated the bands. The number of distorted bands was divided by almost 16 for the synthetic lanes and by 7 for the test dataset of real lanes. This method can be applied effectively to different sample types. It can realign minimal contrast bands and is robust for non-uniform deformations.

N-glycosylation analysis of mouse immunoglobulin G isolated from dried blood spots.

The association of immunoglobulin G (IgG) glycosylation changes with various human diseases and physiological conditions is well established. Since the mechanistical explanation of the regulation of IgG glycosylation and its functional role in these various states is still missing, the eyes of the biomedical community are now turned towards animal models, which enable intervention studies necessary for conclusions on causality. Mice are recognized and used as a good experimental model for human IgG glycosylation. However, smaller blood volumes, low IgG concentrations at young ages (which are most often used in mice experiments) and multiple sampling protocols during the course of longitudinal studies would profit from a robust workflow for mouse IgG glycome analysis from minute amounts of starting material, collected through a simple sampling procedure. For this purpose, we have developed a protocol for analysis of total N-glycans of IgG isolated from mouse dried blood spots (DBS), which we report here. We show that mouse DBS are a good source of material for IgG N-glycan analysis by multiplexed capillary gel electrophoresis with laser-induced fluorescence (xCGE-LIF).

Short communication: Use of a digital refractometer in assessing immunoglobulin G concentrations in colostrum and the first 5 transition milkings in an Irish dairy herd

Transition milk is a source of immunoglobulin G (IgG) and could potentially be used to provide calves with passive immunity, when the IgG concentration is ≥50 g/L. Assessment of IgG concentrations in transition milk would be required before feeding and could be conducted using cow-side tests such as refractometers. Currently, limited information is available on the ability of refractometers to assess transition milk quality. We hypothesized that digital refractometry could be used to provide an accurate cow-side assessment of IgG concentrations in colostrum and transition milk, and IgG concentration in colostrum and one or more transition milking in an Irish herd is >50 g/L. The objectives of this study were to determine the IgG concentrations in colostrum and first, second, third, fourth, and fifth transition milk, and determine the utility of a digital refractometer in assessing quality of colostrum and transition milk produced by cows in a pasture-based dairy production system. A convenient sample of 75 dairy cows were enrolled. Colostrum and transition milk IgG concentrations were determined by radial immunodiffusion and refractometry. Sensitivity and specificity of the refractometer were determined and cut-off points that maximized sensitivity and specificity were determined using receiver operating characteristic curves. Median (range) IgG concentrations in colostrum and first, second, third, fourth, and fifth milking were 99.6, 43.5, 12.5, 5.3, 1.9, and 1.8 g/L, respectively. The sensitivity (0.8-1) of digital refractometry in identifying samples with low IgG concentrations in colostrum, first, second, and third transition milk was acceptable. In contrast, digital refractometry was not useful for assessing IgG concentrations in the fourth and fifth milking due to low IgG concentrations.

Socioeconomic Status Is Associated With Antibody Levels Against Vaccine Preventable Diseases in the Netherlands.

Background: We investigated whether low socioeconomic status (SES), which is associated with reduced health and life expectancy, might play a role in increased risk for infectious diseases. Therefore, we explored the association between SES and immunoglobulin G (IgG) levels against various pathogens.Methods: We analyzed the association between SES [educational level and net household income (NHI)] and serum IgG concentration against measles, mumps, rubella, varicella, Haemophilus influenzae type B (HiB), pneumococcus, meningococcus serogroup C (MenC), and cytomegalovirus (CMV) collected within a national cross-sectional serosurvey (2006/2007) using linear regression analyses among non-vaccinated individuals.Results: Higher educational level was associated with higher IgG concentrations against measles (GMC ratio 1.34, 95% CI 1.18–1.53) and rubella (1.13, 1.02–1.25) compared to low education level. In contrast, higher education level was associated with lower IgG concentrations against pneumococcus (0.78, 0.70–0.88), MenC (0.54, 0.44–0.68), and CMV (0.23, 0.18–0.31) compared to low education level. This pattern was also evident when NHI was used as SES indicator.Conclusion: Our study suggests that socioeconomic status is associated with antibody levels in a pathogen-dependent manner. The results suggest that differences in serological response upon infection or differences in exposure might be involved in the variation in IgG levels between SES groups.

Antibody concentrations against the infecting serotype in vaccinated and unvaccinated children with invasive pneumococcal disease in the United Kingdom, 2006-2013.

This study aimed to estimate, following invasive pneumococcal disease (IPD), the proportion of children with protective immunoglobulin G (IgG) concentrations against the infecting serotype compared with other vaccine serotypes, and to assess risk of recurrent IPD. Pneumococcal antibody concentrations were available for 413 children with vaccine-type IPD diagnosed during 2006-2013. We compared serotype-specific IgG concentrations against the infecting vs other vaccine serotypes, after adjusting for confounders such as age using multilevel analyses. After IPD, a higher proportion of vaccine-naive children had IgG concentrations ≥0.35 µg/mL against their infecting serotype than other vaccine serotypes (51% vs 36%; P < .001). In contrast, among children immunized with pneumococcal conjugate vaccine (PCV) both before and after IPD, the proportion with IgG concentrations ≥0.35 µg/mL against the infecting serotype was lower compared with other vaccine serotypes (71% vs 98%; P < .001). These children also had lower IgG geometric mean concentrations (GMCs) against the infecting serotype (2.22 µg/mL) vs other vaccine serotypes (15.64 µg/mL) in multilevel models (IgG GMC ratio, 0.24; 95% confidence interval, .18-.32), although their IgG GMC was higher compared with vaccine-naive children. Vaccinated children with IgG concentrations <0.35 µg/mL against their infecting serotype generally remained unresponsive despite further vaccine doses. However, recurrent IPD with the same infecting serotype was rare (7/3030 children [0.2%]) and not associated with unresponsiveness. Vaccination with PCV before and/or after IPD was associated with lower IgG concentrations against the infecting serotype compared with other vaccine serotypes, but recurrent IPD was rare. Further studies are needed to understand this phenomenon in immunized children.

Influence of colostral quality on serum proteins in dairy calves raised in smallholder farms in Thailand

The objective of this study was to analyze the influence of colostral quality on serum proteins in calves. Samples were collected from visited farms in Kasetsart University Veterinary Teaching Hospital at Kamphaeng Saen and Nong Pho Animal Hospital. In total, 35 dairy farms contributed 80 dams and calves' samples. Colostrum samples from 80 dairy cows and blood samples from their calves were taken to evaluate colostral immunoglobulins (Ig) and immunoglobulin G (IgG), and calf serum protein and IgG. Total colostral Ig, colostral and serum IgG, and serum protein were measured by a colostrometer, single radial immunodiffusion, and refractrometer, respectively. Immunoglobulin G and serum protein concentrations increased in the 1st day after birth, and maximum concentrations were seen in the 2nd day and then decreased in the 7th and 14th days. Average ± SD total colostral IgG concentrations at calving date and at 1 and 2days after calving were 93.85 ± 33.89, 37.11 ± 23.51, and 17.23 ± 9.4mg/mL, respectively. The profile of total Ig and IgG concentrations in colostrum had a similar pattern, with the maximum concentrations obtained in calving date and rapidly decreased thereafter. Low IgG concentrations were seen in the 7th and 14th day after calving. The calves that were fed with high quality colostrum had higher serum protein at 1day of age, 7.49 ± 1.01g/dL, than calves fed with low quality colostrum, 6.40 ± 0.86g/dL (P < 0.01). The increase in serum protein after first colostrum feeding of high and low quality colostrum was 1.55 ± 1.07 and 0.81 ± 0.69g/dL, respectively (P = 0.02).

Decreased levels of serum complement C3 and natural killer cells add to the predictive value of total immunoglobulin G for severe infection in heart transplant recipients

Infection remains a source of mortality in heart recipients. We previously reported that post-transplant immunoglobulin G (IgG) quantification can help identify the risk for infection. We assessed whether other standardized parameters of humoral and cellular immunity could prove useful when identifying patients at risk of infection. We prospectively studied 133 heart recipients over a 12-month period. Forty-eight patients had at least one episode of severe infection. An event was defined as an infection requiring intravenous antimicrobial therapy. Cox regression analysis revealed an association between the risk of developing infection and the following: lower IgG2 subclass levels (day 7: relative hazard [RH] 1.71; day 30: RH 1.76), lower IgA levels (day 7: RH 1.61; day 30: RH 1.91), lower complement C3 values (day 7: RH 1.25), lower CD3 absolute counts (day 30: RH 1.10), lower absolute natural killer [NK] cell count (day 7: RH 1.24), and lower IgG concentrations (day 7: RH 1.31; day 30: RH 1.36). Cox regression bivariate analysis revealed that lower day 7 C3 levels, IgG2 concentration, and absolute NK cell count remained significant after adjustment for total IgG levels. Data suggest that early immune monitoring including C3, IgG2, and NK cell testing in addition to IgG concentrations is useful when attempting to identify the risk of infection in heart transplant recipients.

Immunoglobulin Deficiency in Cavalier King Charles Spaniels with Pneumocystis Pneumonia

Serum concentrations of immunoglobulin G (IgG), IgM, and IgA were measured in 9 Cavalier King Charles Spaniels with pneumonia caused by Pneumocystis sp that were examined at 4 veterinary surgeries in the United Kingdom (UK) between September 2001 and November 2002. Pneumocystis pneumonia was confirmed in all dogs by visualization of the organism in bronchoalveolar lavage fluid or a transthoracic lung aspirate. Two dogs had a history of demodicosis. Immunoglobulin concentrations also were measured in breed-and age-matched dogs sampled over the same period. IgG concentrations were significantly (P = .000) lower in the affected dogs (median 3.2 mg/mL) than in the control dogs (median 8.5 mg/mL). IgM concentrations were significantly (P = .002) higher in the affected dogs (median 1.95 mg/mL) than in the control dogs (median 1.12 mg/mL). One affected dog had no change in IgG concentration more than 3 months after resolution of infection or vaccination, but did have reduction in IgM concentration after resolution of infection and vaccination. Control dogs had low serum IgG and IgM concentrations, compared with the reference interval for all dogs. Lymphocyte count in blood was normal or high in 7 of 8 affected dogs. The results of this study suggest that there is a defect in immunity in Cavalier King Charles Spaniels that underlies the susceptibility of these dogs to pneumocystosis. Further studies are indicated to elucidate the mechanisms behind the defect, the prevalence within the breed, and the potential mode of inheritance of the problem.

Stability of total and rubella-specific IgG in oral fluid samples: the effect of time and temperature

Oral fluid (saliva) samples are increasingly used as a minimally invasive alternative to serum to detect antibody for viral diagnostics and population-based surveys of immunity to common infections. Postal collection of these samples is convenient, but it is uncertain how oral fluid antibody levels may deteriorate during transit. In this study multiple oral fluid samples, from a group of individuals, were collected and kept at two different temperatures (10 and 20 °C, simulating winter and summer conditions ) for periods of up to 7 days. They were then tested for total immunoglobulin G (IgG) and for rubella-specific IgG. Total IgG concentrations ranged from 2.0 to 48.6 mg/l but showed no significant decrease over the 7-day period. There was also no significant change in rubella-specific IgG measured using an antibody capture ELISA, but testing with an indirect rubella IgG ELISA revealed a significant decrease in absorbance values between day 1 and day 7 at 20 °C. The difference in the rubella assay results may reflect the different assay formats with the signal in the indirect procedure related to the concentration of rubella IgG in the oral fluid sample, rather than the proportion of virus-specific IgG measured with the antibody capture format. The study demonstrated that total and rubella specific IgG in oral fluid samples were stable for up to 7 days at differing temperatures and that an antibody capture assay format should be used for virus-specific testing to minimise inaccurate results due to low IgG concentrations in oral fluid samples.

Increased clearance of IgG in mice that lack beta 2-microglobulin: possible protective role of FcRn.

The mechanisms that regulate immunoglobulin G (IgG) catabolism are little understood. We have previously found unusually low IgG concentrations in sera of mice homozygous for a targeted disruption of the beta 2-microglobulin gene. We therefore investigated whether this might result, at least in part, from increased clearance of IgG from the systemic circulation in mice lacking beta 2-microglobulin. We compared the half-lives of radiolabelled mouse IgG1 injected intravenously into beta 2-microglobulin-/- mice and wild-type or heterozygous siblings. The clearance of 125I-labelled IgG1 was strikingly more rapid in the mice lacking beta 2-microglobulin. beta 2-microglobulin-/- mice lack functional molecules of the MHC class I-related Fc receptor, FcRn. Some mutations in mouse IgG1 that increase its clearance have recently been shown to prevent binding to FcRn in the gut. To determine whether the slower degradation of immunoglobulin in mice with beta 2-microglobulin correlated with the ability of the antibody to bind FcRn, we measured the clearance of chicken IgY, which does not bind this receptor. The 125I-labelled IgY was catabolized equally rapidly in beta 2-microglobulin-deficient and wild-type mice. We compared the half-lives of the four subclasses of mouse IgG in beta 2-microglobulin-/-, +/-, and +/+ mice to determine whether the difference we had noted for IgG1 was peculiar to this subclass. The 125I-labelled IgG of all subclasses, with the possible exception of IgG2b. was degraded more rapidly in the beta 2-microglobulin-deficient mice than in heterozygous or wild-type siblings. These data suggest that FcRn can protect IgG from degradation, and is therefore important in maintaining IgG levels in the circulation.

Complement component 3 binding to Haemophilus influenzae type b in the presence of anticapsular and anti-outer membrane antibodies

Antibodies directed against the capsular polysaccharide (polyribosyl ribitol phosphate [PRP]) or the outer membrane proteins (OMP) of Haemophilus influenzae type b (Hib) promote bactericidal activity, complement 3 (C3) binding, and ingestion by phagocytic cells. To assess the relative contribution of anti-OMP to host defense against Hib, we compared the opsonic activities of anti-PRP and anti-OMP as reflected by the amounts of C3 bound to the bacterial surface. Immunoglobulin G (IgG) fractions containing either anti-PRP or anti-OMP were incubated with Hib in the presence of a C5-deficient complement source. C3, total IgG, and IgG subclasses bound to the bacteria were quantified by enzyme-linked immunosorbent assay. The maximum amount of C3 which could be bound to Hib was greater in the presence of anti-PRP than in the presence of anti-OMP. Also, except at low IgG concentrations, the rate of increase in bound C3 as a function of increasing IgG concentration was greater for anti-PRP than for anti-OMP. Hib-bound anti-OMP consisted primarily of IgG1 and IgG3, whereas bound anti-PRP was primarily IgG1 and IgG2. Thus, the potential for C3 binding to Hib is greater in the presence of anti-PRP than in the presence of anti-OMP, probably because of the larger number of binding sites available to the former. Nonetheless, OMP appear to provide important targets for opsonic antibody and would be logical components of a PRP-conjugate vaccine or may be efficacious as vaccines against nontypeable H. influenzae.

Ability of Monoclonal Antibodies to the Thyrotropin Receptor to Increase Collagen Synthesis in Human Fibroblasts: An Assay which Appears to Measure Exophthalmogenic Immunoglobulins in Graves' Sera

Immunoglobulin G (IgG) preparations from 17 of 20 hyperthyroid patients with Graves' ophthalmopathy stimulated collagen biosynthesis in human fibroblasts, as measured by [3H]proline incorporation. This activity was not associated with thyroid-stimulating antibody (TSAb) activity in a thyroid cell cAMP assay in 50% of the IgG preparations, and it was not found in IgGs from 12 normal subjects, 7 of 8 patients with Graves' hyperthyroidism but no ophthalmopathy, 4 patients with Hashimoto's disease, 7 patients with nontoxic goiter, or 4 hypothyroid patients. In the same assay, 11E8, 22A6, and 13D11, 3 mouse monoclonal antibodies to the bovine TSH receptor, and 307H6, a human monoclonal antibody to the TSH receptor of the thyroid from a Graves' patient with ophthalmopathy, also stimulated [3H]proline incorporation into collagen and were active at more than 1,000- to 10,000-fold lower IgG concentrations (0.1-0.5 microgram/ml as opposed to greater than 1 mg/ml). 11E8 and 13D11 are TSH binding inhibitory antibodies (TBIAbs); 22A6 and 307H6 are TSAbs in cAMP assays. Two other mouse anti-TSH receptor monoclonal antibodies, both TBIAbs, as well as 8 human monoclonal antibodies to the TSH receptor from Graves' patients with or without ophthalmopathy (2 TBIAbs and 6 TSAbs) were negative or significantly less potent (greater than 50 fold) in the assay. The fibroblast activity of the monoclonal antibodies was lost if the antibodies were preincubated with thyroid membranes, was significantly decreased when fibroblasts were exposed to mild trypsin treatment before the assay, was not inhibited by human asialoagalacto-thyroglobulin, and required more than a TSH receptor determinant, since TSH alone neither duplicated nor inhibited the antibody activity. In summary, an assay for measuring the activity of autoantibodies active in causing ophthalmopathy is described, and some but not all TSH receptor monoclonal antibodies have been found to duplicate the action of the autoimmune IgGs from the ophthalmopathy patients.

Characterization of the optimal stimulatory effects of graves' monoclonal and serum immunoglobulin G on adenosine 3',5'-monophosphate production in fRTL-5 thyroid cells: a potential clinical assay.

Immunoglobulin G (IgG) preparations derived from the sera of patients with hyperthyroidism due to Graves' disease (TSAb) as well as a monoclonal IgG derived from heterohybridoma fusions of Graves' lymphocytes augmented cAMP levels in a continuous strain of functioning rat thyroid cells (clone FRTL-5) in culture. Optimal stimulation was the same for both types of IgG preparations when measured after 2 h of incubation with 5 X 10(4) cells/well and using cells maintained in a nongrowth, TSH-deficient medium for 7 days. At low IgG concentrations, the stimulatory activities of both preparations exhibited a linear dependence on concentration and similar Ka values (approximately 4 X 10(-8) M) despite the fact that 65% of the Graves' serum IgG preparations had a significantly better ability to inhibit TSH binding to membrane preparations. The Ka value for TSH in the same assay was about 5 X 10(-12) M. Using this cell assay, 90% of a series of hyperthyroid Graves' IgG preparations exhibited stimulating activity, a value comparable to the frequency of positive results found by ourselves and others using human thyroid cell and slice systems. In contrast, only 10% of patients who were euthyroid 1 yr after antithyroid drug withdrawal (n = 21) exhibited stimulating activity, and no stimulating activity was detected in patients with nontoxic nodular goiter (n = 11), toxic adenoma (n = 5), or thyroid carcinoma (n = 6). The studies suggest that an optimized rat FRTL-5 thyroid cell system is a clinically useful and convenient alternative to human thyroid cell and slice systems for detecting TSAbs.