Are there any clinical indications for measuring IgG subclasses?

Nephelometry vs. Immunoturbidimetry assay: Analytical performance on IgG subclasses

Interest in measuring immunoglobulin G Subclasses (IgG Subclasses) is increasing as more information is gathered and understanding regarding conditions associated with deficiencies of each IgG Subclass grows. Different methodologies are available for the measurement of IgG Subclasses, but their specificities vary. As a result, laboratories choose the methodology that better suits their routine, but which may not necessarily align with the needs of their population. In addition, the lack of standardization for the quantification of IgG Subclasses causes diagnostic gaps when comparing results provided by different methodologies. Thus, the purpose of our research is to compare the analytical performance of The Binding Site's (TBS) Optilite® human Immunoglobulin G (IgG) and IgG Subclasses Immunoturbidimetry assay, with the Nephelometry method routinely used in our clinical laboratory, Siemens BNII®. Our results show that the Immunoturbidimetry assay appears to be the most reliable to evaluate IgG Subclasses: the sum of IgG Subclasses and Total IgG correlate better than by Nephelometry. Although these methodologies share a similar principle, the comparison of results appears to be compromised. Therefore, prior to switching methodologies, further studies should be conducted to assess which methodology could be better applied to specific populations. It is also essential to standardise IgG Subclasses assays to reduce discrepancies that arise from comparing results.

Factors associated with IgG levels in adults with IgG subclass deficiency

Background

Factors associated with IgG levels in adults with IgG subclass deficiency (IgGSD) are incompletely understood. We studied adults with IgGSD with subnormal IgG1 only, subnormal IgG1/IgG3, or subnormal IgG3 only without other subnormal IgG subclasses, IgA, or IgM. We compiled: age; sex; autoimmune condition(s) (AC); atopy; IgG, IgG subclasses, IgA, IgM; IgGsum (IgG1 + IgG2 + IgG3 + IgG4); and D (percentage difference between IgGsum and IgG). We compared attributes of patients with/without subnormal IgG (< 7.00 g/L; subnormal IgG1 subclass groups only) and analyzed IgGsum and IgG relationships. We performed backward stepwise regressions on IgG using independent variables IgG subclasses, age, and sex and on D using independent variables age and sex.

Results

There were 39 patients with subnormal IgG1 only (89.7% women), 53 with subnormal IgG1/IgG3 (88.7% women), and 115 with subnormal IgG3 only (91.3% women). Fifteen patients (38.5%) and 32 patients (60.4%) in the respective subnormal IgG1 subclass groups had subnormal IgG. Attributes of patients with/without IgG < 7.00 g/L were similar, except that AC prevalence was lower in patients with subnormal IgG1 only and IgG < 7.00 g/L than ≥ 7.00 g/L (p = 0.0484). Mean/median IgG1 and IgG2 were significantly lower in patients with IgG < 7.00 g/L in both subnormal IgG1 subclass groups (p < 0.0001, all comparisons). Regressions on IgG in three subclass groups revealed positive associations with IgG1 and IgG2 (p < 0.0001 each association). Regressions on D revealed no significant association. IgG1 percentages of IgGsum were lower and IgG2 percentages were higher in patients with subnormal IgG1 subclass levels than subnormal IgG3 only (p < 0.0001 all comparisons).

Conclusions

We conclude that both IgG1 and IgG2 are major determinants of IgG in patients with subnormal IgG1, combined subnormal IgG1/IgG3, or subnormal IgG3 and that in patients with subnormal IgG1 or combined subnormal IgG1/IgG3, median IgG2 levels are significantly lower in those with IgG < 7.00 g/L than those with IgG ≥ 7.00 g/L.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12865-021-00447-3.

Impact of Tocilizumab (Anti-IL-6R) Treatment on Immunoglobulins and Anti-HLA Antibodies in Kidney Transplant Patients With Chronic Antibody-mediated Rejection

BACKGROUND

Chronic antibody-mediated rejection (cAMR) results in the majority of renal allograft losses. Currently, there are no approved therapies. We recently reported on clinical use of tocilizumab (TCZ) for treatment of cAMR in HLA-sensitized kidney transplant patients. IgG1 and IgG3 subclasses of IgG are potent effectors of complement- and antibody-dependent cellular cytotoxicity, which are critical mediators of AMR. Here, we examined the impact of TCZ treatment for cAMR on total IgG, IgG1-4 subclasses, and anti-HLA-IgG (total and subclasses).

METHODS

Archived plasma obtained pre- and post-TCZ treatment (8 mg/kg, 6×, monthly) from 12 cAMR patients who failed standard of care treatment with intravenous immune globulin + rituximab with or without plasma exchange were tested for total IgG and IgG1-4 by ELISA, anti-HLA-total IgG, IgG3 and IgG4, and donor-specific antibody by Luminex assay. Archived plasma from 14 cAMR patients treated with the standard of care were included as controls.

RESULTS

Total IgG and IgG1-3 were significantly reduced post-TCZ, whereas no reduction was seen post-treatment in the control group. Of 11 patients, 8 (73%) showed reduction of anti-HLA-total IgG and IgG3 post-TCZ, but this was not statistically significant.

CONCLUSIONS

TCZ reduced total IgG and IgG1-3 and anti-HLA-total IgG and IgG3 levels, suggesting that TCZ suppresses Ig production in B cells nonspecifically, likely through inhibition of interleukin 6-mediated signaling to B cells and plasma cells. This may be a contributing factor for the beneficial effect of TCZ on cAMR observed in this patient population.

Antibody deficiency testing for primary immunodeficiency: A practical review for the clinician

OBJECTIVE

To review selected published studies related to the diagnostic evaluation of antibody deficiency.

DATA SOURCES

Published literature.

STUDY SELECTIONS

Studies related to the diagnostic evaluation of antibody deficiency and existing recommendations were selected.

RESULTS

Many primary immunodeficiency diseases include humoral deficiency. Practical tests used in the clinical evaluation of patients for possible antibody deficiency include immunoglobulin measurement, specific antibody titers, and B-cell enumeration and phenotyping.

CONCLUSION

Clinically available tests can be used to readily evaluate patients for antibody deficiencies.

Immunoglobulin G (IgG) and IgG subclass reference intervals in children, using Optilite® reagents

Background:

Immunoglobulin G (IgG) and IgG subclass assays are indicated in patients with suspected primary immunodeficiency (PID). Commercially available assays for IgG subclass determination are calibrated against various preparations, and so specific reference values are required for each of them. Using Optilite® reagents from The Binding Site Group Ltd., we sought to determine the pediatric IgG and IgG subclass reference intervals with respect to the ERM-DA470k certified reference material.

Methods:

Levels of IgG and IgG subclasses were analyzed in serum samples collected from a large cohort of PID-free children and adolescents. Reference intervals were calculated for previously published age groups (6–12 months, 12–18 months, 18 months–2 years, 2–3 years, 3–4 years, 4–6 years, 6–9 years, 9–12 years and 12–18 years), according to the Clinical and Laboratory Standards Institute’s C28-A3c protocol.

Results:

A total of 456 serum samples were analyzed. The correlation between the total IgG and the sum of the IgG subclasses was good (r2=0.96). No statistically significant gender-specific differences were observed. Our results for the changes over time in IgG and IgG subclass levels are consistent with previous reports. The differences between our lower/upper reference limits and those in the literature are probably due to variations in calibration.

Conclusions:

Our present results provide a reliable basis for the diagnosis of PIDs in childhood and for the accreditation of laboratories using Optilite® immunoturbidimetric reagents for IgG subclass measurement. Laboratory scientists and clinicians should be aware of the need for manufacturer-specific IgG subclass reference intervals.

Serum IgG subclass levels and risk of exacerbations and hospitalizations in patients with COPD

BACKGROUND

The literature is scarce regarding the prevalence and clinical impact of IgG subclass deficiency in COPD. We investigated the prevalence of IgG subclass deficiencies and their association with exacerbations and hospitalizations using subjects from two COPD cohorts.

METHODS

We measured IgG subclass levels using immunonephelometry in serum samples from participants enrolled in two previous COPD trials: Macrolide Azithromycin for Prevention of Exacerbations of COPD (MACRO; n = 976) and Simvastatin for the Prevention of Exacerbations in Moderate-to-Severe COPD (STATCOPE; n = 653). All samples were collected from clinically stable participants upon entry into both studies. IgG subclass deficiency was diagnosed when IgG subclass levels were below their respective lower limit of normal: IgG1 < 2.8 g/L; IgG2 < 1.15 g/L; IgG3 < 0.24 g/L; and IgG4 < 0.052 g/L. To investigate the impact of IgG subclass levels on time to first exacerbation or hospitalization, we log-transformed IgG levels and performed Cox regression models, with adjustments for confounders.

RESULTS

One or more IgG subclass deficiencies were found in 173 (17.7%) and 133 (20.4%) participants in MACRO and STATCOPE, respectively. Lower IgG1 or IgG2 levels resulted in increased risk of exacerbations with adjusted hazard ratios (HR) of 1.30 (95% CI, 1.10-1.54, p < 0.01) and 1.19 (95% CI, 1.05-1.35, p < 0.01), respectively in the MACRO study, with STATCOPE yielding similar results. Reduced IgG1 or IgG2 levels were also associated with increased risk of hospitalizations: the adjusted HR for IgG1 and IgG2 was 1.52 (95% CI: 1.15-2.02, p < 0.01) and 1.33 (95% CI, 1.08-1.64, p < 0.01), respectively for the MACRO study; in STATCOPE, only IgG2 was an independent predictor of hospitalization. In our multivariate Cox models, IgG3 and IgG4 levels did not result in significant associations for both outcomes in either MACRO or STATCOPE cohorts.

CONCLUSIONS

Approximately 1 in 5 COPD patients had one or more IgG subclass deficiencies. Reduced IgG subclass levels were independent risk factors for both COPD exacerbations (IgG1 and IgG2) and hospitalizations (IgG2) in two COPD cohorts.

TRIAL REGISTRATION

This study used serum samples from participants of the MACRO ( NCT00325897 ) and STATCOPE ( NCT01061671 ) trials.

Clinical and pathological characteristics of IgG4-related interstitial lung disease

IgG4-related interstitial lung disease (IgG4-RILD), which is characterized by increased IgG4 levels, IgG4⁺ plasma cell infiltration and irregular whorled fibrosis, is a recently described lung disorder that belongs to the group of systemic fibroinflammatory IgG4-related diseases (IgG4-RD). The aim of the present study was to improve the current knowledge regarding the specific clinical and histopathological characteristics of IgG4-RILD and to investigate its underlying immune mechanism in vivo. A total of 7 patients newly diagnosed with IgG4-RILD were enrolled in the present study (4 men and 3 women; mean age, 57 years; range, 29–71 years). Patients' clinical history was collected and serological indicators, including C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), antinuclear antibodies (ANAs) and tumor markers were measured. Serum immunoglobulin G (IgG), IgE and IgG4 levels were also evaluated. In addition, computed tomographic (CT) images and pathological examinations were used to determine the characteristics of lung lesions in all patients. The majority of patients presented with symptoms of fever, cough and dyspnea, while allergic symptoms were also encountered. The laboratory examination results revealed different degrees of increased CRP, ESR, tumor markers, ANA, serum IgE and IgG4. The CT images revealed diffuse ground glass opacities, bronchiectasis and thickened bronchovascular bundles. Histologically, the lung lesions were characterized by dense IgG4⁺ lymphoplasmacytic infiltrates intermixed with extensive fibrous tissue hyperplasia and an irregularly storiform pattern of fibrosis. The mean number of IgG4⁺ plasma cells was >10 cells/high power field. The ratio of IgG/IgG4⁺ plasma cells was >50% in inflamed lesions and the number of parenchymal cells was markedly reduced. Obliterative phlebitis or obliterative arteritis was observed in all patients. In conclusion, the clinicopathological similarities between IgG4-RILD and other IgG4-RD suggest that IgG4-related immunopathological processes may be associated with the pathogenesis of pulmonary lesions. Future studies based on the findings herein may elucidate the specific pathological process underlying the development of this fibroinflammatory disorder.

Similar but not consistent: Revisiting the pitfalls of measuring IgG subclasses with different assays

BACKGROUND

Laboratory quantification of IgG subclasses (IgGSc) is a well-established second-line tool for differential diagnosis of immune deficiencies. However, so far there is still no internationally approved standard available for IgGSc, and different assays are prone to produce divergent results. In this study, we evaluated the comparability and equivalence of two commercially available IgGSc assays, one being the Siemens IgGSc assay on a BN ProSpec analyzer and the other being The Binding Site (TBS) IgGSc assay on a Roche cobas c502 analyzer.

METHODS

We analyzed a total of 50 patient plasma samples obtained over a 3-month period with both IgGSc assays and compared the resulting data based and the CLSI EP09-A3 method comparison guideline.

RESULTS

Depending on the analyzed IgGSc type, the average relative differences in IgGSc concentration (g/L) between the two assays were considerable, starting with -13.5% for IgG1 and 11.3% for IgG2, over -47.3% for IgG4, and up to 52.9% for IgG3. Applying the assay-specific reference intervals, the classification agreement (below, within, or above the reference range) ranged from 88% to 90% for the individual subclasses. However, only 68% of samples showed an overall classification agreement.

CONCLUSION

The comparability of the two IgGSc assays proved to be limited and might be considered similar at best on the diagnostic level. Laboratory specialists as well as clinicians therefore should be cautious when using and interpreting IgGSc measurements obtained with different assays or analyzers.

Identification and quantification of immunoglobulin G (G1, G2, G3 and G4) in human blood plasma by high-resolution quadrupole-Orbitrap mass spectrometry

We described a method for quantification of IgG (IgG1, IgG2, IgG3 and IgG4) in a small amount of human blood plasma using high-resolution quadrupole-Orbitrap mass spectrometry (HR-Q-Orbitrap-MS).

Elevated Serum IgG4 Levels in Diagnosis, Treatment Response, Organ Involvement, and Relapse in a Prospective IgG4-Related Disease UK Cohort

OBJECTIVES

Elevated serum immunoglobulin G4 (IgG4) levels have been associated with autoimmune pancreatitis and IgG4-related disease (IgG4-RD) for over a decade. However, an elevated serum IgG4 is not specific for the disease. There have been inconsistent reports of its use in diagnosis, as a marker of disease relapse, and its relationship to organ involvement in retrospective cohorts. The aims of this study were to ascertain conditions that are associated with an elevated serum IgG4 and to investigate the role of IgG4 in diagnosis, relapse, and organ involvement in a prospective cohort of patients with IgG4-RD.

METHODS

We evaluated serum IgG4 measurements in the Oxford Immunology Laboratory over 6 years. Patients in whom serum IgG4 was requested to differentiate IgG4-RD from other diseases were recruited into a longitudinal follow-up study to determine final diagnosis. In a prospective cohort of IgG4-RD patients, organ involvement, response to therapy, and disease relapse were determined.

RESULTS

Two thousand and sixty-seven samples from 1,510 patients had serum IgG4 measured. Of these, IgG4 was elevated (≥1.4 g l(-1)) in 243 (16.1%) patients. The main indication (85.6%) was to distinguish between IgG4-RD and non-IgG4-RD conditions. Only 5.1% of patients who had serum IgG4 measured for this purpose had a final diagnosis of IgG4-RD. Of those with an elevated serum IgG4, 22.4% met IgG4-RD diagnostic criteria. Serum IgG4 was elevated in 48 (82.8%) of IgG4-RD patients. An IgG4 cutoff of 1.4 g l(-1) gave a sensitivity of 82.8% and specificity of 84.7% to diagnose IgG4-RD. Increasing this to 2.8 g l(-1) increased specificity to 96.2% and negative predictive value to 97.7%, with a lower sensitivity of 56.9% and positive predictive value of 44.5%. Serum IgG4 levels fell with corticosteroid therapy, but this was not disease-specific. A serum IgG4 of ≥2.8 g l(-1) at diagnosis was associated with multi-organ involvement and risk of relapse.

CONCLUSIONS

Serum IgG4 levels are elevated in multiple non-IgG4-RD inflammatory and malignant conditions, with less than one-quarter of those with an elevated IgG4 meeting IgG4-RD diagnostic criteria. A serum IgG4 of ≥2.8 g l(-1) is useful in distinguishing between IgG4-RD and non-IgG4-RD diagnoses, predicting multiple-organ involvement and risk of relapse in IgG4-RD.

Primary immunodeficiency association with systemic lupus erythematosus: review of literature and lessons learned by the Rheumatology Division of a tertiary university hospital at São Paulo, Brazil

Primary immunodeficiency disorders (PID) represent a heterogeneous group of diseases resulting from inherited defects in the development, maturation and normal function of immune cells; thus, turning individuals susceptible to recurrent infections, allergy, autoimmunity, and malignancies. In this retrospective study, autoimmune diseases (AIDs), in special systemic lupus erythematosus (SLE) which arose associated to the course of PID, are described. Classically, the literature describes three groups of PID associated with SLE: (1) deficiency of Complement pathway components, (2) defects in immunoglobulin synthesis, and (3) chronic granulomatous disease (CGD). Currently, other PID have been described with clinical manifestation of SLE, such as Wiskott-Aldrich syndrome (WAS), autoimmune polyendocrinopathy candidiasis ectodermal dystrophy (APECED), autoimmune lymphoproliferative syndrome (ALPS) and idiopathic CD4(+) lymphocytopenia. Also we present findings from an adult cohort from the outpatient clinic of the Rheumatology Division of Universidade Federal de São Paulo. The PID manifestations found by our study group were considered mild in terms of severity of infections and mortality in early life. Thus, it is possible that some immunodeficiency states are compatible with survival regarding infectious susceptibility; however these states might represent a strong predisposing factor for the development of immune disorders like those observed in SLE.

IgG4 subclass-specific responses to Staphylococcus aureus antigens shed new light on host-pathogen interaction

IgG4 responses are considered indicative for long-term or repeated exposure to particular antigens. Therefore, studying IgG4-specific antibody responses against Staphylococcus aureus might generate new insights into the respective host-pathogen interactions and the microbial virulence factors involved. Using a bead-based flow cytometry assay, we determined total IgG (IgGt), IgG1, and IgG4 antibody responses to 40 different S. aureus virulence factors in sera from healthy persistent nasal carriers, healthy persistent noncarriers, and patients with various staphylococcal infections from three distinct countries. IgGt responses were detected against all tested antigens. These were mostly IgG1 responses. In contrast, IgG4 antibodies were detected to alpha-toxin, chemotaxis inhibitory protein of S. aureus (CHIPS), exfoliative toxins A and B (ETA and -B), HlgB, IsdA, LukD, -E, -F, and -S, staphylococcal complement inhibitor (SCIN), staphylococcal enterotoxin C (SEC), staphylococcal superantigen-like proteins 1, 3, 5, and 9 (SSL1, -3, -5, and -9), and toxic shock syndrome toxin 1 (TSST-1) only. Large interpatient variability was observed, and the type of infection or geographical location did not reveal conserved patterns of response. As persistent S. aureus carriers trended toward IgG4 responses to a larger number of antigens than persistent noncarriers, we also investigated sera from patients with epidermolysis bullosa (EB), a genetic blistering disease associated with high S. aureus carriage rates. EB patients responded immunologically to significantly more antigens than noncarriers and trended toward even more responses than carriers. Altogether, we conclude that the IgG4 responses against a restricted panel of staphylococcal antigens consisting primarily of immune modulators and particular toxins indicate important roles for these virulence factors in staphylococcal pathogen-host interactions, such as chronicity of colonization and/or (subclinical) infections.

Characterization of immunoglobulin by mass spectrometry with applications for the clinical laboratory

Studies monitoring immunoglobulin (Ig) antigen specificity have brought to light key Ig biomarkers for immunity, autoimmunity, cancer detection, and immune system function evaluation. A fundamentally new approach to the detection of Igs based on the primary structure of the Ig is beginning to emerge in the literature. This approach has only become feasible in light of advances in proteomics and rapid improvements in mass spectrometry (MS). Driven primarily by the development of Ig pharmaceuticals, Ig MS-based proteomic methods are revealing structural features which were previously unavailable with other characterization techniques. The task of adapting these techniques to clinical chemistry is in its infancy, but these methods have the potential to dramatically alter testing for Ig biomarkers. The purpose of this article is to review the advances that have been made in proteomic characterization of Igs by MS and the early attempts to apply these methods to clinical samples.

Association between Fc-gamma receptor IIa (CD32) gene polymorphism and malaria susceptibility: a meta-analysis based on 6928 subjects

BACKGROUND

Previous studies about the association between the -131R/H polymorphism in the Fc-gamma receptor IIa (FcγRIIa) gene and malaria susceptibility have yielded conflicting results. The aim of this meta-analysis was to clarify more accurately the association of this polymorphism with malaria risk.

METHODS

A systematic literature search of the associated studies up to August 1, 2013, was conducted using the following electronic databases: PubMed, Embase, Medline, and the China National Knowledge Infrastructure (CNKI). Statistical analyses were performed by STATA12.0 software, with odds ratios (ORs) and their 95% confidence intervals (CIs).

RESULTS

Six eligible studies including 4111 malaria cases and 2817 controls were identified. A pooled analysis of these studies pointed to a significant association between the variant H allele and reduced susceptibility to malaria or possible protection against malaria: H vs. R (OR=0.691, POR=0.009); HH vs. RR (OR=0.523, POR=0.013); RH vs. RR (OR=0.770, POR=0.037); RH+HH vs. RR (OR=0.664, POR=0.019); and HH vs. RH+RR (OR=0.649, POR=0.037). In subgroup analysis, similar significant associations were also found in Asia (HH vs. RR: OR=0.137, POR=0.009; HH vs. RH+RR: OR=0.267, POR=0.000) and in Africa (RH vs. RR: OR=0.842, POR=0.002; RH+HH vs. RR: OR=0.859, POR=0.004).

CONCLUSIONS

This meta-analysis suggests that the variant H allele of the FcγRIIa-131R/H polymorphism may be a protective factor against blood-stages of malaria infection, both in Asians and Africans. The finding may aid the development of effective immune protection strategies against malaria that focus on antibody responses and enrich current knowledge of gene polymorphism in the malaria. Further large and well-designed studies are needed to confirm this association.

Immunization with a multisubunit vaccine considerably reduces establishment of infective larvae in a rodent model of Brugia malayi

Although recombinant vaccines have several advantages over conventional vaccines, protection induced by single antigen vaccines is often inadequate for a multicellular helminth parasite. Therefore, immunoprophylactic efficacy of cocktail antigen vaccines comprised of several combinations of three Brugia malayi recombinant proteins BmAF-Myo, Bm-iPGM and Bm-TPP were evaluated. Myosin+TPP and iPGM+TPP provided the best protection upon B. malayi infective larval challenge with ∼70% reduction in adult worm establishment over non-vaccinated animals that was significantly higher than the protection achieved by any single antigen vaccine. Myosin+iPGM, in contrast did not provide any enhance protection over the single recombinant protein vaccines. Specific IgG, IgM level, IgG antibody subclasses levels (IgG1, IgG2a, IgG2b, IgG3), lymphocyte proliferation, reactive oxygen species level and cytokines level were also determined to elucidate the characteristics of the protective immune responses. Thus the study undertaken provided more insight into the cocktail vaccination approach to combat LF.

The Fcγ receptor IIA-H/H131 genotype is associated with bacteremia in pneumococcal community-acquired pneumonia

OBJECTIVE

To assess the potential association of the functional polymorphism rs1801274 in the receptor IIa for the Fc portion of immunoglobin G (FcγRIIa) gene (FCGR2A-H131R) with the susceptibility to and the severity of community-acquired pneumonia (CAP).

DESIGN

Multicenter prospective and observational study.

SETTING

Four university hospitals in Spain.

PATIENTS

FCGR2A-H131R polymorphism was determined in 1,262 patients with CAP and in 1,224 in the subject control group.

MEASUREMENTS AND MAIN RESULTS

Severe sepsis was recorded in 366 patients. No significant differences in genotype or allele frequencies were seen among patients with CAP or pneumococcal CAP (PCAP) and controls. Patients with bacteremic PCAP (B-PCAP) had significantly higher frequencies of FCGR2A-H/H131 genotypes than those with nonbacteremic PCAP (p = .00016, odds ratio = 2.9, 95% confidence interval 1.58-5.3). The differences remained significant when adjusting for pneumonia severity index, hospital of origin, and intensive care unit admission (p = .0012, odds ratio = 2.83, 95% confidence interval 1.51-5.32). B-PCAP was associated with a significantly higher severity of the disease, evaluated as sepsis severity (p = .000007, odds ratio = 4.40, 95% confidence interval 2.31-8.39), multiorgan dysfunction syndrome (0.00048, odds ratio = 3.29, 95% confidence interval 1.69-6.41), intensive care unit admission, acute renal failure, and acute respiratory distress syndrome.

CONCLUSIONS

Our results do not support a role of FCGR2A-H131R polymorphism in susceptibility to CAP or PCAP. However, we provide the insight that homozygosity for FCGR2A-H131 predisposes B-PCAP, which was associated with higher severity in our study.

Longitudinal analysis of serological responses of adults to Helicobacter pylori antigens

Because Helicobacter pylori persist for decades in the human stomach, the aim of this study was to examine the long-term course of H. pylori-specific serum immunoglobulin G (IgG) responses with respect to subclass and antigenic target. We studied paired serum samples obtained in 1973 and in 1994 in Vammala, Finland, from 64 healthy H. pylori-positive adults and from other healthy control subjects. H. pylori serum immunoglobulin A, IgG, and IgG subclass responses were determined by antigen-specific enzyme-linked immunosorbent assays. H. pylori-specific IgG1 and IgG4 subtype responses from 47 subjects were similar in 1973 and 1994, but not when compared with unrelated persons. H. pylori-specific IgG1:IgG4 ratios among the participants varied >1000-fold; however, 57 (89.1%) of 64 subjects had an IgG1:IgG4 ratio >1.0, consistent with a predominant IgG1 (Th1) response. Furthermore, ratios in individual hosts were stable over the 21-year period (r = 0.56; P < .001). The immune response to heat shock protein HspA was unchanged in 49 (77%) of the 64 subjects tested; of the 15 whose serostatus changed, all seroconverted and were significantly younger than those whose status did not change. These findings indicate that H. pylori-specific antibody responses are host-specific with IgG1:IgG4 ratios stable over 21 years, IgG1 responses predominating, and HspA seroconversion with aging.

Hypogammaglobulinaemia

This article reviews the primary immunodeficiencies that result in hypogammaglobulinemia or predominantly antibody deficiency disorders. This group makes up the largest proportion of patients with primary immunodeficiency. Significant advances have been made in understanding the molecular basis and clinical characteristics of patients with the more severe forms of antibody deficiency in the last 6 years. Recognition of these disorders remains poor with significant diagnostic delay. The milder forms of antibody deficiency disorders, especially those with normal total serum immunoglobulin G levels, remain poorly characterized and understood. Further work remains to be done in understanding and recognizing these syndromes to benefit patient care and foster further knowledge of the immune system.

Immunologic evaluation of patients with recurrent ear, nose, and throat infections

PURPOSE

In this study, we aimed to study the frequency of possible underlying immunodeficiency responsible for susceptibility to ear, nose, and throat (ENT) infection.

MATERIALS AND METHODS

One hundred three (72 males and 31 females) consecutive children and adult patients with history of recurrent or chronic ENT infections, referred by otolaryngologists to the Department of Allergy and Clinical Immunology, Children's Medical Center, Tehran University of Medical Sciences (Tehran, Iran), were enrolled to the study from March 2003 to March 2006. For each patient, demographic information and medical histories of any ENT infections were collected by reviewing the patient's records. We measured immunoglobulin isotype concentrations and immunoglobulin (Ig) G subclasses by nephelometry and enzyme-linked immunosorbent assay methods, respectively. Of 103 patients, 75 received unconjugated pneumococcus polyvalent vaccine, and blood samples were taken before and 21 days after vaccination. Specific antibodies against whole pneumococcal antigens were measured using enzyme-linked immunosorbent assay method. Existence of bronchiectasis was confirmed in each patient using high resolution computed tomography scan.

RESULTS

Among 103 patients, 17 (16.5%) patients were diagnosed to have defects in antibody-mediated immunity including 6 patients with immunoglobulin class deficiency (2 common variable deficiency and 4 IgA deficiency), 3 with IgG subclass deficiency (2 IgG2 and 1 IgG3), and 8 with specific antibody deficiency against polysaccharide antigens. In our series, bronchiectasis was detected in 5 cases associated with primary immunodeficiency.

CONCLUSIONS

Long-standing history of ENT infections could be an alarm for ENT infections associated with primary antibody deficiency.

Antibody deficiency: Table 1

Antibody deficiencies may arise as primary disorders or secondary to a variety of diseases, drugs and other environmental/iatrogenic factors. Significant primary antibody deficiencies are relatively rare but, collectively, account for the majority of primary immunodeficiency syndromes encountered in clinical practice. The genetic basis of a number of primary deficiencies has been clarified, although there is considerable genotype/phenotype heterogeneity and the role of gene/environment interactions has yet to be fully elucidated. Primary antibody deficiency can present at any age. The hallmark clinical presentation is recurrent bacterial infection, but these disorders are also associated with a wide variety of other infectious and non-infectious complications and with a high incidence of chronic, structural tissue damage, particularly in the respiratory tract. Clinical recognition of primary antibody deficiency is frequently delayed with consequent increased morbidity, diminished quality of life and early mortality. Clinical laboratories can contribute to improved and timely detection through awareness of routine test results which may be overtly or indirectly suggestive of antibody deficiency. Secondary deficiency is associated with increased awareness, better recognition and earlier diagnosis than in primary disorders. Early liaison and referral of patients with suspected antibody deficiency for specialist opinion and prompt, appropriate therapy is central to the achievement of good clinical outcomes.

Detection of altered N-glycan profiles in whole serum from rheumatoid arthritis patients

Altered N-glycosylation occurs in many diseases. In rheumatoid arthritis (RA), for example, reduction in galactose residues in IgG and an increase in fucose residues in alpha1-acid glycoprotein have been observed. To further analyse N-glycans in disease, we show N-glycan profiling from whole serum employing reversed phase high performance liquid chromatography/negative-ion mode by sonic spray ionization ion trap mass spectrometry with pyridylamination. Profiles from female 15 RA patients and 18 aged-matched healthy women were compared. The most significant change seen in RA was decreased levels of mono-galactosyl bi-antennary N-glycans, in agreement with the previous reports regarding IgG. We also show previously unreported differences between isomers and increased tri-antennary oligosaccharides. These results indicate that LC-MS analysis of whole serum N-glycans can identify N-glycan alterations in RA and that this is a promising method both for studies of RA mechanisms and diagnosis.

Campylobacter sepsis with multiple organ failure in IgG subclass deficiency

Some patients with immunodeficiency develop clinical features of autoimmune disorders. A previously asymptomatic antibody deficiency can underlie the development of autoimmune diseases and a severe course of infection, with a risk of sepsis; such cases are known in selective IgA deficiency. On the other hand, little information is available on selective IgG subclass deficiencies. An unexpectedly severe course of Campylobacter infection in a 19-year-old woman with a previously undiagnosed complex immune disorder, including selective IgG1 immunodeficiency, Hashimoto's autoimmune thyroiditis with hypothyroidism combined with Addison's disease presumably due to autoimmune adrenalitis, autoimmunity and allergy is described. The pathophysiological mechanisms of autoimmunity in latent humoral defects are discussed.

Isotype-specific detection of ABO blood group antibodies using a novel flow cytometric method

Several methods to detect anti-A/B antibodies based on haemagglutination and haemolysis have been described. These methods measure predominantly anti-A/B immunoglobulin (Ig)M, whereas anti-A/B IgG and IgG subclasses are less well examined. We established a flow cytometry method (ABO-fluorescence-activated cell sorting; ABO-FACS) to quantify binding of anti-A/B IgM, IgG and IgG subclasses to human A or B red blood cells. Anti-A/B IgM were present in the majority of 120 blood donors, as expected from blood group typing. The sensitivity and specificity of anti-A/B IgM to predict the blood group was 93% and 96% respectively. Anti-A/B IgG was found in 34/38 blood group O samples (89%). Anti-B IgG in blood group A or anti-A IgG in blood group B was present in 4/28 (14%) and 1/28 (4%) samples, respectively, and absent in 26 AB sera. IgG2 was the predominant IgG subclass. The correlation of anti-A/B IgM and IgG in the ABO-FACS with haemagglutination titres was 0.870 and 0.783, respectively (n = 240; P < 0.001) whereas the comparison of ABO-FACS with ABO-enzyme-linked immunosorbent assay was less significant. In conclusion, ABO-FACS is a valid method to quantify anti-A/B IgM, IgG and IgG subclasses. It opens the possibility of isotype-specific monitoring of anti-A/B antibodies levels after ABO-incompatible solid organ and stem cell transplantation.

Polymorphism of the Fcgamma receptor IIA and malaria morbidity

Fc receptors (FcRs) are expressed on the surface of all types of cells of the immune system. They bind the Fc portion of immunoglobulin (Ig), thereby bridging specific antigen recognition by antibodies with cellular effector mechanisms. FcγRIIA, one of the three receptors for human IgG, is a low-affinity receptor for monomeric IgG, but binds IgG immune complexes efficiently. FcγRIIA is believed to play a major role in eliciting monocyte- and macrophage-mediated effector responses against blood-stage malaria parasites. A G → A single nucleotide polymorphism, which causes an arginine (R) to be replaced with histidine (H) at position 131, defines two allotypes which difer in their avidity for complexed human IgG₂ and IgG₃. Because FcγRIIA-H131 is the only FcγR allotype which interacts efficiently with human IgG_2, this polymorphism may determine whether parasite-specific IgG₂ may or may not elicit cooperation with cellular imune responses during blood-stage malaria infection. Here, we review data from four published case-control studies describing associations between FcγRIIA R/H131 polymorphism and malaria-related outcomes and discuss possible reasons for some incongruities found in these available results.

Allergic diseases and asthma in relation to serum immunoglobulins and salivary immunoglobulin A in pre-school children: a follow-up community-based study

BACKGROUND

We have previously reported an association between low IgA and allergic manifestations in early childhood (0-2 years) and have now followed our cohort for an additional 2 years.

OBJECTIVE

To evaluate in a longitudinal community-based cohort study the association between maturation of Ig production and allergic manifestations in the first 4 years of life.

METHODS

A cohort of 161 randomly selected children was followed from birth to the age of 42-48 months and evaluated at 18-23 months (EV1; n = 179) and again at the age of 42-48 months (EV2; n = 161). Diagnoses were made with the help of a clinical questionnaire, physical examination and skin prick tests (SPTs) to 10 common allergens. Serum immunoglobulins were measured at EV1 and EV2, and salivary IgA (sal-IgA) at EV2.

RESULTS

Serum IgA, IgE, IgG1, IgG2 and IgG4 increased from 2 to 4 years of age (P < 0.001) and their levels showed close correlations (P < or = 0.01 for most comparisons). Children with one or more positive SPTs had lower serum IgA (P = 0.004) and IgG4 (P = 0.05) at EV2 than those who did not respond, and children who developed allergic rhinitis between EV1 and EV2 had low sal-IgA (P = 0.006) and IgG3 (P < 0.05) at EV2. Atopic eczema was associated with low sal-IgA at EV2, and children who developed eczema between EV1 and EV2 had significantly lower sal-IgA than those who recovered after EV1 (P = 0.02).

CONCLUSION

Allergic manifestations in predisposed children may be influenced by the rate of maturation of immunological components that counteract sensitization or inhibit effector mechanisms of allergy.

Reduction of nasal colonization of nontypeable Haemophilus influenzae following intranasal immunization with rLP4/rLP6/UspA2 proteins combined with aqueous formulation of RC529

Nontypeable Haemophilus influenzae (NTHi) and Moraxella catarrhalis are common causative agents of human mucosal infections. To formulate a mucosal vaccine against these pathogens, recombinant lipidated P4 (rLP4) and P6 (rLP6) proteins of NTHi and ubiquitous cell surface protein A (UspA) of M. catarrhalis were used for active immunization experiments in a mouse nasal challenge model. BALB/c mice were immunized intranasally with these proteins formulated with a chemically synthesized adjuvant, RC529 in an aqueous formulation (RC529-AF). Three weeks after the last immunization, these animals were challenged intranasally with NTHi strain SR7332.P1 and nasal colonization measured 3 days later. To determine local and systemic immune responses, bronchoalveolar washes (BAW) and sera were collected prior to NTHi challenge. The serum and mucosal samples were analyzed by ELISA for rLP4, rLP6 and UspA2 protein-specific IgG, IgG subclass and IgA antibody titers and bactericidal titers were determined against the TTA24 and 430-345 strains of M. catarrhalis. Results of these experiments show that these proteins combined with RC529-AF administered intranasally to mice elicited (1) significantly increased rLP4/rLP6/UspA2 protein-specific circulating IgG and IgA antibody responses; (2) local rLP4/rLP6/UspA2-specific IgA responses in the respiratory tract; and (3) more than a two log reduction of nasal colonization of NTHi strain SR7332 from the nasal tissues of mice. The serum IgG subclass distribution was predominantly IgG2a, representing a Th1 response. The antiserum also exhibited bactericidal activities to several strains of M. catarrhalis. These data indicate that intranasal immunization with rLP4/rLP6/UspA2 proteins combined with RC529-AF may be able to provide a way for inducing local mucosal immunity and for prevention of otitis media in children.

Functional and molecular evaluation of lymphocytes

The laboratory plays a central role in the evaluation of immune function and is critical in the diagnosis and treatment of immune deficiencies. The range of options available to evaluate lymphocyte function has expanded dramatically as our understanding of the immune system has expanded. As the choices of laboratory tests increase, so also does the need to choose testing in such a way as to appropriately direct the evaluation. Typically, this approach involves starting with screening tests and, on the basis of the results of these tests, deciding whether more sophisticated and expensive testing is warranted. The remarkable developments over the past decade leading to the identification of numerous gene defects underlying a variety of immune deficiencies has moved mutation analysis into the realm of the clinical laboratory. This information could be indispensable for immune deficiency diagnosis, prenatal screening, carrier detection, and family counseling. In this review a sequential approach to evaluating lymphocyte function is presented, starting with readily available screening tests and followed by more complex in vitro testing, including the application of newer assays. The various approaches are presented from the perspective of appropriate use and information garnered, whereas actual details of test procedures are not discussed but are referenced. The evolution of immune function testing suggests that it will continue to develop, and future assays are likely to provide even more insight into specific aspects of the immune response and be linked to immune deficiencies not yet defined.

Associations between plasma DDE levels and immunologic measures in African-American farmers in North Carolina

Experimental studies in rodents demonstrate evidence of immunosuppressive effects of dietary exposure to DDT [2,2-bis((italic)p(/italic)-chlorophenyl)-1,1,1-trichloroethane], but human data pertaining to immunomodulating effects of DDT exposure are limited. In this study we examined the association between the persistent organochlorine breakdown product 1,1-dichloro-2,2,bis(p-chlorophenyl)ethylene p,p'-DDE) and immunologic measures using blood samples in a relatively highly exposed population of farmers in the United States. Levels of serum immunoglobulin A (IgA) and IgG and the prevalence of antinuclear antibodies in relation to plasma p,p'-DDE levels were evaluated in samples from 137 African-American male farmers (30-88 years of age; median, 64 years). Participants were recruited through black churches in four rural counties in eastern North Carolina. Data collection included a telephone interview pertaining to farming practices and health history, and one blood sample was collected from each participant. Linear and logistic regression, adjusting for age, cholesterol, triglycerides, smoking status, and years of any kind of pesticide use, was used to assess the association between immunologic parameters and plasma levels of p,p'-DDE. The median plasma p,p'-DDE concentration was 7.7 microg/L (range, 0.6-77.4 microg/L). There was no association between p,p'-DDE and IgA in any of the models. IgG levels decreased with increasing p,p'-DDE levels, with a statistically significant decrease of approximately 50% in the highest two categories of exposure (greater than or equal to 6.0 microg/L) compared with values of < 3.0 microg/L. Sixteen (12%) were positive for antinuclear antibodies. The prevalence of antinuclear antibodies was somewhat elevated in the highest category of p,p'-DDE exposure (odds ratio, 1.9; 95% confidence interval, 0.32-11.3; for > or = 12.0 microg/L compared with < 3.0 microg/L p,p'-DDE), but this difference was not statistically significant. These analyses provide evidence that p,p'-DDE modulates immune responses in humans.