Clinical and immunologic characteristics of healthy children with subnormal serum concentrations of IgG2

Immunoglobulin A deficiency in children, an undervalued clinical issue

Immunoglobulin A (IgA) is the principal antibody in secretions that bathe the gastrointestinal and respiratory mucosal surfaces and acts as an important first line of defense against invasion of pathogenic micro-organisms. The reported prevalence rate of complete IgA deficiency in healthy children ranges from 1:170 to 1:400, and as a solitary condition, it is often considered of limited clinical importance. However, patients with IgA deficiency can develop recurrent respiratory and gastrointestinal infections, as well as allergic and autoimmune diseases. In children referred for recurrent respiratory tract infections, the observed prevalence rate increases more than tenfold. This review discusses several aspects of IgA deficiency in children, including immunologic and microbiome changes in early childhood and the potential consequences of this condition in later life. It illustrates the importance of early identification of children with impaired IgA production who deserve appropriate clinical care and follow-up.

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.

The Clinical Utility of Measuring IgG Subclass Immunoglobulins During Immunological Investigation for Suspected Primary Antibody Deficiencies

Measurement of IgG subclass concentrations is a standard laboratory test run as part of a panel to investigate the suspicion of antibody deficiency. The assessment is clinically important when total IgG is within the normal age-specific reference range. The measurement is useful for diagnosis of IgG subclass deficiency, to aid the diagnosis of specific antibody deficiency, as a supporting test for the diagnosis of common variable immunodeficiency, as well as for risk stratification of patients with low IgA. The measurement of IgG subclasses may also help determine a revaccination strategy for patients and support patient management. In certain circumstances, the measurement of IgG subclasses may be used to monitor a patient’s humoral immune system. In this review, we discuss the utility of measuring IgG subclass concentrations.

The Challenge of Immunoglobulin-G Subclass Deficiency and Specific Polysaccharide Antibody Deficiency--a Dutch Pediatric Cohort Study

PURPOSE

Immunoglobulin(Ig)G-subclass deficiency and specific polysaccharide antibody deficiency (SPAD) are among the most frequent causes of recurrent respiratory infections in children. Little is known about their prevalence, clinical presentation and prognosis. No study has been published in a Western-European nor in a mainly non-tertiary cohort until now. Therefore, we performed this observational cohort study in children recruited from secondary and tertiary pediatric practices all over The Netherlands.

METHODS

Dutch pediatricians were monthly asked to report patients with IgG-subclass deficiency and/or SPAD. Demographic, clinical and laboratory characteristics were collected. Separate informed consent was asked from parents and children (≥ 12 years of age) for annual update of the medical status.

RESULTS

49 children with confirmed IgG-subclass deficiency and/or SPAD were included. The majority of children (69%) was reported by four (out of 12) secondary hospitals with a pediatric immunologist in the staff. 45 children had ≥ 1 low IgG-subclass level and 11 had SPAD. IgG2 deficiency was the most prevalent IgG-subclass deficiency (37/49;76%). 10% of these children already showed bronchiectasis. Two-thirds were male (33/49;67%, p = 0.015). From 10 years of age, only boys were left and only boys showed progressive immunodeficiency during follow-up (11/24; 46%).

CONCLUSIONS

This is the first Western-European mainly non-tertiary cohort of children with IgG-subclass deficiency and/or SPAD. The disease course is not always benign, especially in boys. Most children were reported and managed in secondary hospitals with a pediatric immunologist in the staff. To identify more patients, the awareness of these diseases among general pediatricians should increase.

Hypermucoviscous Klebsiella syndrome without liver abscess in a patient with immunoglobulin g2 immune deficiency

Background

 Hypermucoviscous Klebsiellapneumoniae (HMVKP) emerged as a cause of invasive infections in South-East (SE) Asia. It has become the most common cause of liver abscess in that region, and it is a significant causative organism in endogenous endophthalmitis and meningitis. During the past decade, cases of this uniquely virulent organism have been reported outside of SE Asia, with a propensity to affect individuals of SE Asian descent. Cases have been reported from North America including Canada.

Methods

 We report a case of a patient of Filipino descent living in Canada who presented with recurrent HMVKP bacteremia in the absence of pyogenic liver abscess or other localized metastatic Klebsiella infection.

Results

 Investigations identified an immunoglobulin (Ig)G2 deficiency and low IgM indicating potential common variable immunodeficiency, and administration of intravenous immunoglobulins was associated with prevention of further recurrences.

Conclusions

 To our knowledge, this is the first report of HMVKP associated with predisposing antibody deficiency.

Primary ciliary dyskinesia and humoral immunodeficiency--is there a missing link?

BACKGROUND

Primary ciliary dyskinesia (PCD) and humoral mmunodeficiency (HID) are both rare disorders which cause recurrent upper and lower respiratory tract infections.

OBJECTIVE

To examine the concurrence of PCD and HID in a patient cohort with known PCD.

METHODS

Retrospective review of the patient files.

RESULTS

We describe 11 patients of a cohort of 168 patients with PCD (6.5%) with a combination of PCD and some form of HID. The patients all presented with typical clinical symptoms for PCD, however the role of the concomitant immunological abnormalities is not clear.

CONCLUSION

PCD and HID coincided in 6.5% of the patients. We suggest that a common pathophysiological pathway results in both disorders.

Imbalanced anti-H1N1 immunoglobulin subclasses and dysregulated cytokines in hospitalized pregnant women with 2009 H1N1 influenza and pneumonia in Shenyang, China

Influenza virus can cause an acute respiratory illness of variable intensity. In our study, we describe the clinical and immunological characteristics of pregnant and nonpregnant women who were hospitalized with 2009 H1N1 influenza and pneumonia in Shenyang, China, from November 2009 to January 2010. Forty-two female patient infected with H1N1 were divided into groups according to pregnancy. Clinical data were collected. Cytokines and anti-H1N1 IgG subclasses were detected. We observed significant lymphopenia, hypoproteinemia, reduced CD4(+)T cell counts and CD4(+)/CD8(+) ratios, reduced anti-H1N1 IgG subclasses IgG2 and IgG3 constituent ratios, elevated C reactive protein and interleukin-10 levels with regard to nonpregnant H1N1 group. Compared with the healthy pregnant group, the pregnant H1N1 group showed elevated aspartate aminotransferase and glutamic alanine aminotransferase levels, an increased interferon-gamma and interleukin-10 levels and reduced anti-H1N1 IgG subclasses IgG2, IgG3 and IgG4 combination ratios. There was a statistically significant association between imbalanced anti-H1N1 immunoglobulin subclasses and dysregulated cytokines in pregnant women with H1N1 infection.

The spectrum of disease manifestations in patients with common variable immunodeficiency disorders and partial antibody deficiency in a university hospital

Background

Common variable immunodeficiency disorders (CVIDs) represents a heterogeneous disease spectrum that includes recurrent infections and complications such as autoimmunity, inflammatory organ disease and an increased risk of cancer. A diagnostic delay is common in CVIDs patients.

Purpose

To determine the spectrum of clinical manifestations, immunological characteristics, and the time to diagnosis of 61 adult CVIDs and 18 patients with a partial antibody deficiency (SADNI and IgG subclass deficiency).

Methods

A retrospective cohort study was performed in patients who met the ESID/PAGID for CVIDs, IgG subclass deficiency and SADNI. Medical records were reviewed to obtain patient demographics, clinical and laboratory data.

Results

Infections were the main presentation of all antibody deficient patients and the number of patients with infections declined during IgG therapy. The development of bronchiectasis continued despite IgG therapy, as well as the development of autoinflammatory conditions. Non-infectious disease complications were present in 30% of CVIDs patients at the time of diagnosis and this increased to 51% during follow up despite IgG therapy. The most common complications were autoimmunity or lymphoproliferative disease. The median time to diagnosis was 10 years and in the patients with non-infectious complications the time to diagnosis was considerably longer when compared to the group of patients without complications (17.6 vs. 10.2 years, p = 0.026).

Conclusion

In contrast to the partial antibody deficiencies we found a considerable delay in the diagnosis of CVIDs, especially in those patients who were dominated by non-infectious complications, and thus increased awareness would be beneficial. Pulmonary and other complications may continue despite adequate IgG replacement therapy suggesting other causes responsible for these complications.

Electronic supplementary material

The online version of this article (doi:10.1007/s10875-012-9671-6) contains supplementary material, which is available to authorized users.

Diagnosis and treatment of primary immunodeficiency disease: the role of the otolaryngologist

OBJECTIVE

The objective of the study was to review the diagnosis and treatment of primary immunodeficiency disease (PID) and the role of otolaryngologists in the management of PID.

METHODS

A search was conducted of PubMed and the Web sites of organizations for PID patients for literature pertaining to the diagnosis and treatment of PID, with an emphasis on the role of otolaryngologists. The reference lists of selected articles were reviewed for additional articles.

RESULTS

Patients with PID commonly present with respiratory tract infections (eg, recurrent ear, nose, or throat infections) and chest disease. Diagnostic delays or inadequate treatment of PID may lead to significant morbidity and premature mortality. Immunoglobulin (Ig) replacement is the cornerstone of therapy for most patients with PID. Although intravenous Ig is the most popular route of administration in the United States, subcutaneous Ig administration may be appropriate for patients with poor venous access, those who are unable to tolerate intravenous Ig, or those who prefer the independence and flexibility of self-administration.

CONCLUSIONS

Recognition and diagnosis of PID by otolaryngologists are critical to optimizing patient outcomes. Several therapeutic regimens for Ig replacement are now available that offer patients increased flexibility and independence.

Pathogenesis, diagnosis, and management of primary antibody deficiencies and infections

Primary antibody deficiencies are the most common primary immunodeficiency diseases. They are a heterogeneous group of disorders with various degrees of dysfunctional antibody production resulting from a disruption of B-cell differentiation at different stages. While there has been tremendous recent progress in the understanding of some of these disorders, the etiology remains unknown for the majority of patients. As there is a large spectrum of underlying defects, the age at presentation varies widely, and the clinical manifestations range from an almost complete absence of B cells and serum immunoglobulins to selectively impaired antibody responses to specific antigens with normal total serum immunoglobulin concentrations. However, all of these disorders share an increased susceptibility to infections, affecting predominantly the respiratory tract. A delay of appropriate treatment for some diseases can result in serious complications related to infections, while timely diagnosis and adequate therapy can significantly decrease morbidity and increase life expectancy and quality of life.

Primary Immunodeficiencies

Primary immunodeficiencies (PIDs), once considered to be very rare, are now increasingly recognized because of growing knowledge in the immunological field and the availability of more sophisticated diagnostic techniques and therapeutic modalities [161]. However in a database of >120,000 inpatients of a general hospital for conditions suggestive of ID 59 patients were tested, and an undiagnosed PID was found in 17 (29%) of the subjects tested [107]. The publication of the first case of agammaglobulinemia by Bruton in 1952 [60] demonstrated that the PID diagnosis is first done in the laboratory. However, PIDs require specialized immunological centers for diagnosis and management [33]. A large body of epidemiological evidence supports the hypothesis of the existence of a close etiopathogenetic relation between PID and atopy [73]. In particular, an elevated frequency of asthma, food allergy (FA), atopic dermatitis and enteric pathologies can be found in various PIDs. In addition we will discuss another subject that is certainly of interest: the pseudo-immunodepressed child with recurrent respiratory infections (RRIs), an event that often requires medical intervention and that very often leads to the suspicion that it involves antibody deficiencies [149].

Low serum immunoglobulin G2 levels in infancy can be transient

OBJECTIVE

The immunoglobulin G2 subclasses contain predominantly antipolysaccharide antibodies. It was therefore believed intuitively that low immunoglobulin G2 levels could predispose individuals to infections with encapsulated bacteria. Although many reports initially supported this notion, more recent studies challenged it. Regardless of the biological significance, the natural history of low immunoglobulin G2 levels has not been carefully studied.

METHODS

We studied the outcome of low serum immunoglobulin G2 subclass levels in children. Thirteen patients who were referred because of recurrent infections were found to have low immunoglobulin G2 levels. Laboratory evaluation at presentation and follow-up visits included total serum immunoglobulins, immunoglobulin subclasses, and specific antibodies to protein antigens and to pneumococcal vaccine.

RESULTS

Low immunoglobulin G2 levels resolved completely within 0.6 years to 6 years (median: 1.5 years) in all patients. All 13 patients responded adequately to vaccination with protein antigens such as tetanus toxoid and polio as well as to immunization with pneumococcal vaccine. Four of 13 patients had a previous history of transient hypogammaglobulinemia, raising the possibility that the other cases may simply represent the tail end of this condition.

CONCLUSION

We have demonstrated that low immunoglobulin G2 detected in early infancy and childhood is likely to resolve completely within several months and up to 6 years from the time of presentation.

Increases in serum immunoglobulins to age-related normal levels in children with IgA and/or IgG subclass deficiency

Immunoglobulins (Ig) A and G subclass deficiencies are common immune system disorders which cause morbidity especially between 2 and 6 yr of age. Prognosis of these defects and therapeutic approach is unclear. The aim of the present retrospective study was to review the clinical and laboratory records of 87 children with IgA and/or IgG subclass deficiency to determine whether these patients experience changes in serum Ig concentrations during follow-up and to give more clinic and laboratory information to the families about the course of these diseases. Among 87 patients studied, the most frequent defect was partial IgA deficiency combined with IgG3 subclass deficiency (41%). The other groups were as follows; partial IgA deficiency (32%), selective IgA deficiency (8%), partial IgA combined with IgG2-G4 subclass deficiency (6%), and IgG subclass deficiency (13%). The commonest clinical presentations were recurrent upper respiratory tract infections (76%), pneumonia (14%), acute gastroenteritis (3%), urinary tractus infection (3%), sinusitis (2%), and acute otitis media (2%). Atopy was widely represented in the patients studied (24%). The number of patients who were given prophylactic treatment with benzathine penicilline, prophylactic oral antibiotic, or oral bacterial extract to prevent infections was 68 (78%). Frequency of recurrent infections decreased from 7.9 +/- 4.9 per year to 2.5 +/- 2.3 in 68 patients receiving any prophylactic regimen; however, decrease in frequency of infections did not show any significant difference between different prophylactic groups. None of the patients in the selective IgA deficiency group had reached normal serum levels of IgA. At the age of 58.3 +/- 21.4 months, 52% of patients in partial IgA deficiency group and 51% of patients in partial IgA + IgG subclass deficiency group, serum IgA increased to normal ranges. Serum IgG subclass levels increased to normal range for age in 67% of patients in partial IgA + IgG subclass deficiency group and in 30% of patients in isolated IgG subclass deficiency group. The mean age for reaching age-related normal IgG subclass levels for these patients was 69.0 +/- 14.5 months. In conclusion, findings of this study suggest that IgA and/or IgG subclass deficiency may be either progressive or reversible disorders and emphasize the value of monitoring Ig levels in affected individuals.

Current perspectives on primary immunodeficiency diseases

Since the original description of X-linked agammaglobulinemia in 1952, the number of independent primary immunodeficiency diseases (PIDs) has expanded to more than 100 entities. By definition, a PID is a genetically determined disorder resulting in enhanced susceptibility to infectious disease. Despite the heritable nature of these diseases, some PIDs are clinically manifested only after prerequisite environmental exposures but they often have associated malignant, allergic, or autoimmune manifestations. PIDs must be distinguished from secondary or acquired immunodeficiencies, which are far more common. In this review, we will place these immunodeficiencies in the context of both clinical and laboratory presentations as well as highlight the known genetic basis.

Low gammaglobulin subclass 2 levels in paediatric cystic fibrosis patients followed over a 2-year period

The aim of this study was to relate serum immunoglobulin G2 subclass levels in a large paediatric population with cystic fibrosis, to clinical status and antibody levels to Haemophilus influenzae type b and Streptococcus pneumoniae and to observe any changes over a 2-year period. IgG subclasses were measured in 131 patients. Results were compared with levels from age-related normal population data. The following clinical data were collected at baseline and 2 years later; genotype: height, weight, and BMI z-scores: FEV1 (as percent predicted): Shwachman-Kulczcyki and Northern chest X-ray scores: Pseudomonas aeruginosa status. Antibody levels to H. influenzae type b and S. pneumoniae measured at baseline were related to IgG2 level. There was a reduction in the prevalence of low levels of IgG2 from 29% to 10% over the 2-year period. Low levels of IgG2 were not associated with any decline in clinical well-being. Low levels of IgG2 alone were associated with low antibody levels to S. pneumoniae. Low levels of IgG2 and low levels of antibody to H. influenzae and S. pneumoniae were not associated with any decline in clinical well-being. Children with high levels of IgG2 had worse lung function, worse Shwachman-Kulczcyki and Northern chest X-ray scores and higher levels of P. aeruginosa infection. Children with low IgG2 levels were not worse clinically compared to those with normal or high IgG2 levels. High IgG2 levels were associated with a worse clinical status.

Clinical and laboratory characteristics of 75 patients with specific polysaccharide antibody deficiency syndrome

BACKGROUND

There are limited studies of large cohorts of patients with specific polysaccharide antibody deficiency (SPAD) syndrome.

OBJECTIVE

To study the clinical and laboratory characteristics of patients with specific polysaccharide antibody deficiency syndrome.

METHODS

We retrospectively studied 75 patients with total IgG levels of at least 500 mg/dL and fewer than 9 of 12 responses to vaccination with pneumococcal vaccine polyvalent. Exclusion criteria included an IgG level less than 500 mg/dL, established immunodeficiency syndrome, and secondary immunodeficiency.

RESULTS

The most common clinical presentation was frequent infections (n = 69; 92%), including sinusitis (n = 53; 77%), pneumonia (n = 29; 42%), ear infections (n = 18; 26%), and bronchitis (n = 19; 28%). Other presentations were systemic infections (n = 5; 7%), autoimmune or rheumatic diseases (n = 6; 8%), and chronic diarrhea (n = 4; 5%). The median IgG2 level of patients with no response to pneumococcal vaccine polyvalent tended to be lower than that of patients with at least 1 response (150 vs 193 mg/dL, respectively; P = .06). There was no association between total IgG level (categorized as 500-600 or > or = 600 mg/dL) and frequency of infection (P = .43). Patients with fewer responses to pneumococcal vaccine polyvalent and a higher frequency of infections were more likely to receive intravenous immunoglobulin (IVIG) therapy (P = .01 and .003, respectively). Treatment with IVIG significantly reduced the number of infections (P < .001).

CONCLUSION

Patients with no response to pneumococcal vaccine polyvalent tended to have lower IgG2 levels; those with fewer responses were more likely to receive IVIG therapy.

Clinical Evaluation and Treatment of the Adult Patient With Suspected Primary Immunodeficiency Disease: A Case Analysis

PURPOSE

To describe immunoglobulin G2 (IgG2) subclass deficiency in the context of primary immunodeficiency disorders, their pathophysiology, epidemiology, clinical evaluation, and management.

DATA SOURCES

Actual case study and extensive review of the scientific and medical literature.

CONCLUSIONS

Consideration should be given to primary immunodeficiency diseases as one possible cause of recurrent upper and lower respiratory tract infections in patients at any age. Early diagnosis and intervention can significantly reduce the burden of these diseases.

IMPLICATIONS FOR PRACTICE

Advanced practice nurses need to keep pace with the ever-expanding field of immunity. Knowledge of basic principles of the immune system facilitates a logical approach to the evaluation and management of primary immunodeficiency diseases.

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.

Primary immunodeficiencies associated with pneumococcal disease

PURPOSE OF REVIEW

Streptococcus pneumoniae may cause disease in patients with a variety of primary immunodeficiencies. However, no previous review has dealt with the issue of which primary immunodeficiencies predispose affected individuals to pneumococcal disease. We thus reviewed the medical literature on cases of S. pneumoniae infection in patients with primary immunodeficiency diseases, with a particular emphasis on invasive pneumococcal disease.

RECENT FINDINGS

Primary immunodeficiency diseases comprise over 100 conditions, each associated with a variety of infections. Patients at high risk for pneumococcal disease include most if not all B-cell defects (whether due to an intrinsic B-cell anomaly or an impaired T-cell help), deficiencies of early components of the classical pathway of complement and C3 deficiency, congenital asplenia, anhidrotic ectodermal dysplasia with immunodeficiency (caused by impaired NF-kappaB activation), and interleukin-1 receptor associated kinase-4 deficiency. Patients with other complement deficiencies (alternative and third pathway) and hyperimmunoglobulin E syndrome show a lower risk, whereas patients with other known primary immunodeficiencies, such as phagocytic disorders, do not appear to be particularly vulnerable to S. pneumoniae.

SUMMARY

Antibody- and complement-mediated opsonization, splenic macrophages and interleukin-1 receptor associated kinase-4- and nuclear factor kappaB-mediated immune responses are crucial for protective immunity to S. pneumoniae. This information is useful, not only in increasing our understanding of human immunity to S. pneumoniae, but also in the diagnostic investigation of patients with pneumococcal disease.

Evaluation of the relevance of humoral immunodeficiencies in a pediatric population affected by recurrent infections

Recurrent infections are a common cause of morbidity in childhood. Several reports have associated this condition to low levels of IgA and IgG subclasses and/or lack of specific antipolysaccharide antibody response, although the relevance of these defects in terms of prognosis and therapeutic approach is still unclear. The aim of our study was to determine the frequency and the clinical relevance of humoral immunodeficiency (HID) other than hypogammaglobulinemia in children affected by recurrent infections. We recruited 67 pediatric patients affected by recurrent infections. Serum IgG, IgA, IgM, IgG2, IgG3, and specific anti-Haemophilus influenzae (anti-Hib) antibodies were determined. Thirty-seven out of 67 patients showed antibody defects (55%). IgA deficiency was observed in 21 out of 67 patients (31%), followed by IgG2 (18%), IgG3 (15%) and IgM (6%) defects. Anti-Hib deficiency was present in three out of 44 patients (7%). A tendency for a higher occurrence of pneumonia and otitis, although not statistically significant (p > 0.05), was observed in HID patients compared to children with normal humoral function. No statistical difference as to the frequency of mild infections (URI) was found between HID and non-HID patients. We therefore suggest that the therapeutic program is based on the clinical status of the patients. Long-term follow-up with repeated determinations of antibody levels is crucial, however, to detect those defects that might evolve into more complex immunodeficiencies.

Immunoglobulin G subclass deficiency: fact or fancy?

Over the past four decades, many patients have been reported to have deficiencies of one or more subclasses of immunoglobulin G (IgG), despite normal total IgG serum concentrations. However, except for those with extremely low or absent IgG2 concentrations and an inability to produce antibodies to polysaccharide antigens, it is difficult to know the true biologic significance of the many reported IgG subclass deficiencies. Completely asymptomatic individuals who totally lack IgG1, IgG2, IgG4, or IgA1 because of heavy-chain gene deletions have been described as producing antibodies normally. In addition, numerous healthy children who have low levels of IgG2 but normal responses to polysaccharide antigens when immunized have been similarly described. From these observations, it can be concluded that IgG subclass measurement is not very helpful in the general assessment of immune function. Such assays provide no information about the patient's capacity to produce specific antibodies to protein, polysaccharide, or viral antigens.

Primary immunodeficiency disorders: antibody deficiency

As a group, antibody deficiencies represent the most common types of primary immune deficiencies in human subjects. Often symptoms do not appear until the latter part of the first year of life, as passively acquired IgG from the mother decreases to below protective levels. As with the T-cell immune deficiencies, the spectrum of antibody deficiencies is broad, ranging from the most severe type of antibody deficiency with totally absent B cells and serum Igs to patients who have a selective antibody deficiency with normal serum Ig. In addition to the increased susceptibility to infections, a number of other disease processes (eg, autoimmunity and malignancies) can be involved in the clinical presentation. Fortunately, the availability of intravenous immune serum globulin has made the management of these patients more complete. Recently, molecular immunology has led to identification of the gene or genes involved in many of these antibody deficiencies. As discussed in this review, this has led to a better elucidation of the B-cell development and differentiation pathways and a more complete understanding of the pathogenesis of many of these antibody deficiencies.

Immunoglobulins in chronic renal failure of childhood: effects of dialysis modalities

BACKGROUND

It is not clear whether low serum levels of IgG (subclasses), previously demonstrated in children on peritoneal dialysis (PD), are related to the PD procedure or to factors associated with chronic renal failure (CRF). The aim of our study was to analyze the effect of PD on serum and PD effluent (PDE) IgG and subclass levels in children with end-stage renal failure.

METHODS

We measured albumin, IgG, IgA, IgM, and IgG subclasses in serum and PDE from children on PD (N = 40) and compared the serum values with those of children treated with hemodialysis (HD, N = 23) or presenting with CRF but not yet dialyzed (CRF; N = 63), and with a group of healthy controls (HCs; N = 67). Sixteen PD children could be followed sequentially from before starting PD and eight during a peritonitis episode.

RESULTS

Forty percent of the PD children showed reduced serum IgG2 levels (P = 0.0003) compared with 35% in HD (P = 0.006), 33% in CRF (P = 0.001), and 9% in HC children. IgG1 deficiencies were observed in 25% of PD patients (P < 0.0001), 4% of HD (P = NS), 16% of CRF (P = 0.0005), and 0% of HC children. IgG3 and IgG4 deficiencies were observed less frequently. Peritoneal clearances were similar for total IgG, IgG1, IgG2, and IgG4, but were lower for IgG3 (P < 0.05). No relationships were found between clearances and age or duration of PD treatment. Total IgG (P = 0. 003) and IgG1 (P = 0.002) levels declined just after starting PD. Peritonitis was associated with temporarily increased peritoneal loss of Ig, while the serum concentrations were unaffected. No significant relationship was found between the peritonitis incidence and reduced IgG or subclasses. However, all children with two or more peritonitis episodes per year had a reduced Ig level.

CONCLUSIONS

Although the mean serum concentrations of immunoglobulins were normal in all studied groups, a deficiency of one or more IgG subclasses was present in all groups with renal failure, suggesting inhibition of their synthesis by the uremic state. Ig deficiencies were more frequently found in PD, likely caused by protein loss in PDE. A high peritonitis incidence was associated with reduced serum Ig levels.

IgG subclasses in wheezing infants

The wheezing infant is a common but difficult patient to approach diagnostically. The prevalence of IgG subclass antibody deficiency in wheezing infants is still controversial. We studied serum concentration of IgG subclasses in 38 wheezing infants (aged 6-24 months who had not received systemic steroids before investigation) and in 30 healthy age matched control (aged 6-24 months). The prevalence of one or more IgG subclass deficiency was 31.6% in wheezing infants and 26.7% in controls. There was no significant difference in prevalence of IgG subclass deficiency between patients and controls (p > 0.05). The mean concentration of IgG subclasses in patients were compared with controls. There was no significant difference in mean serum concentration of IgG1, G2 and G3 subclasses. But there was a trend towards higher concentrations of IgG4 in wheezing infants and this difference for IgG4 was significant (p < 0.01). However, IgG subclass deficiency was found in 25% and 36.4% of wheezing infants who had experienced from two to four and five or more wheezing episodes in two years, respectively (p > 0.05). These findings suggest that wheezing in infancy is not associated with IgG subclass deficiency and in wheezing infants low IgG subclass levels do not increase the frequency of wheezing.

Immunoglobulin G subclasses in wheezing infants

BACKGROUND

The wheezing infant is a common but difficult patient to approach diagnostically. The prevalence of immunoglobulin (Ig) G subclass deficiency in wheezing infants is still controversial.

METHODS

We studied the serum concentration of IgG subclasses in 38 wheezing infants (aged 6-24 months) who had not received systemic steroids before investigation and in 30 healthy age matched controls (aged 6-24 months).

RESULTS

The prevalence of one or more IgG subclass deficiencies was 31.6% in wheezing infants and 26.7% in controls. There was no significant difference in prevalence of IgG subclass deficiency between patients and controls (P > 0.05). The mean concentration of IgG subclasses in patients were compared with controls. There was no significant difference in mean serum concentration of IgG1, G2 and G3 subclasses. However, there was a trend towards higher concentrations of IgG4 in wheezing infants and this difference for IgG4 was significant (P < 0.01). Immunoglobulin G subclass deficiency was found in 25 and 36.4% of wheezing infants who had experienced from two to four and five or more wheezing episodes in 2 years, respectively (P > 0.05).

CONCLUSION

Our findings suggest that wheezing in infancy is not associated with IgG subclass deficiency, and in wheezing infants low IgG subclasses levels do not increase the frequency of wheezing. However, there is a relationship between recurrent wheezing and serum IgG4 subclass concentration.

Response to pneumococcal immunization in children with and without recurrent infections

Many children with recurrent sinopulmonary infections fail to mount an adequate humoral response following immunization with polysaccharide antigens. At present there are no controlled studies comparing responses to pneumococcal immunization in children with recurrent infections and a healthy, age-matched cohort. Immunological evaluation was performed on 66 children with recurrent sinopulmonary infections, aged 2-5 years (mean 3.06 +/- 0.92). A control group included 28 healthy, age-matched controls (mean 3.14 +/- 0.88 years). Both groups were immunized with 23 valent pneumococcal vaccine, and titers were measured before and 4 weeks after immunization. Antibody levels to 12 pneumococcal serotypes were measured via radioimmunoassay. Geometric preimmunization mean titers in the control group were 215.5 +/- 157 ngAbN/ml rising to 989.5 +/- 745 ngAbN/ml compared to 77.71 +/- 38.4 ngAbN/ml increasing to 446.7 +/- 406 ngAbN/ml in the study group (p < .05). Serotypes 3, 4, 7F, 8, 9N, and 18C were the most immunogenic, while serotypes 6A and 14 were the least. Overall, the control group responded to 7.71 +/- 1.24 serotypes versus 5.1 +/- 2.0 in the study group (p < .05), where postimmunization titers at least doubled and rose to > or = 300 ngAbN/ml. All controls responded to at least five or more serotypes, 26/28 responded to 6 or more. In contrast, only 38/66 (57%) of study patients responded to five or more serotypes, and only 27/66 (41%) responded to at least 6 of 12. Preimmunization titers of greater than 300 ngAbN/ml were present in 30% (102/336) of the control serotypes; however, only 53 of these (52%) doubled post immunization; 22% of the elevated titers decreased post immunization. Markedly elevated titers > or = 500 ngAbN/ml were present in 20% (69/336) of the preimmunization serotypes, only 39% of these doubled post immunization. Twenty-three valent pneumococcal vaccine is immunogenic in young, healthy children. A significant percentage of children with recurrent sinopulmonary infections fail to produce adequate serotype specific antibodies following pneumococcal immunization.

Open trial of intravenous immune serum globulin for chronic sinusitis in children

BACKGROUND

Chronic sinusitis in children is a complex clinical problem. Some patients do not improve with medical therapy and some fail surgery as well.

OBJECTIVE

A therapeutic trial of intravenous immune serum globulin (IVIG) was given to children whose sinus disease was recalcitrant to the usual therapeutic modalities. The objective of IVIG administration was to modulate the inflammatory process contributing to the chronicity of the sinusitis.

METHODS

Six patients were given a 12-month trial of monthly (400 mg/kg) IVIG infusions. Entry criteria included persistence of sinusitis after 3 months of full course antibiotics, or two episodes of sinusitis within a 3-month period while on prophylactic antibiotics. All patients had abnormal sinus CT (computerized tomography) scans at entry. Three of the six patients remained symptomatic despite prior sinus surgery. Patients with primary immune deficiencies were excluded. Each patient served as his own control based on their previous 12-month history and clinical course. Four of the 6 patients were atopic as demonstrated by prick skin testing; however, all patients had nasal eosinophilia.

RESULTS

Full course antibiotic use decreased in five of the six patients (183 to 84 days); correspondingly, the episodes of sinusitis decreased (average 9 to 4 per year). In addition, sinus CT scans showed significant improvement.

CONCLUSION

This preliminary open-trial of IVIG suggests its usefulness as adjunct therapy to medical management in selected patients with chronic sinus disease. The mechanism(s) by which IVIG may be helpful is probably not based on the concept of replacement therapy, but more likely as an immune or inflammatory modulating agent.

Cartilage-hair hypoplasia associated with IgG2 deficiency

We report on a 1 year old boy with cartilage-hair hypoplasia (CHH). He suffered from recurrent upper respiratory infections and short-limbed dwarfism. As with most patients with CHH, he had impaired cellular immunity as determined by lymphocyte reactivity. In addition, he had a selective IgG2 deficiency. This combination of immunodeficiencies has not previously been reported for patients with CHH. His recurrent upper respiratory infections were likely to be associated with cellular immunodeficiency and IgG2 deficiency.

Recurrent pneumococcal meningitis in a patient with transient IgG subclass deficiency

We report the case of a 3 year old boy who exhibited recurrent serious infections with a transient imbalance of IgG subclass in the second year of life. He suffered from pneumococcal meningitis at 3 months, hepatitis at 9 months, and purulent arthritis at 11 months of age. The second episode of pneumococcal meningitis occurred at 14 months. Serum IgG level was normal for age. Low level of IgG2, undetectable level of IgG4 and negligible level of pneumococcus-specific IgG1-G2 antibodies were found. No other primary immunodeficiency was apparent. Serum IgG2-G4 levels but not pneumococcus-specific IgG1-G2 titers increased by the age of 30 months. At that time, he was inoculated with a polyvalent pneumococcal vaccine along with acellular diphtheria-pertussis-tetanus vaccine. He acquired the immunity against these agents, and had no episodic infections in the following 2 years. This observation stresses the existence of transient IgG subclass deficiency associated with delayed development of the anti-polysaccharide antibody response.

Age related IgG subclass concentrations in asthma

The prevalence of IgG subclass deficiency in asthma is still controversial. Earlier studies often included patients receiving treatment with systemic steroids which can induce hypogammaglobulinaemia. Concentrations of IgG subclasses were studies in 200 children (aged 2-17 years) with asthma (mean asthma severity score (ASS) 2, range 1-4) who had not received systemic steroids for at least six weeks before investigation, and in 226 healthy age matched controls. The mean concentrations of IgG subclasses in children with asthma were within the 1SD range of those of the control group. In the group with asthma there was a trend towards higher levels of IgG1 and IgG4, whereas the number of children with low concentrations of IgG2 (< 2 SD of control serum samples; absolute concentrations 0.08-1.25 g/l) was slightly greater than in the group who did not have asthma (4.5 v 2.2%). Patients with subnormal concentrations of IgG2 could not be distinguished clinically or on the basis of case history and additional immunological studies did not show further abnormalities. Patients with severe asthma (ASS 3-4) had significantly higher concentrations of IgG4 (mean (SE) 0.53 (0.09) v 0.26 (0.04) g/l) than patients with mild asthma (ASS 1). No significant difference in subclass concentration was found between patients with atopic and those with non-atopic asthma. It is concluded that in an unselected group of children with asthma the mean IgG subclass concentrations do not differ significantly from a group of healthy age matched controls.

Successful intravenous immunoglobulin therapy for recurrent pneumococcal otitis media in young children

Serum immunoglobulin levels and naturally occurring antibody titres against Streptococcus pneumoniae were measured in seven children aged 1-1.9 years with recurrent pneumococcal acute otitis media (AOM). Three of them had low IgG2 levels. Mean antibody levels of anti-pneumococcal IgG1 and anti-pneumococcal IgG2 were significantly lower in patients when compared to those of healthy controls and children who had less frequent episodes of AOM. Following treatment with intravenous immunoglobulin (IVIG) for 6 months, anti-pneumococcal IgG1 and IgG2 antibody levels increased and the number of episodes of AOM decreased in all patients. Following the discontinuation of IVIG therapy, no AOM episode occurred. Serum levels of anti-pneumococcal IgG1 and IgG2 were normal, which were measured in three subjects at 5, 6, and 12 months after the cessation of IVIG therapy. These results suggested that delayed maturation of anti-pneumococcal antibody production caused recurrent AOM and this condition was corrected by IVIG therapy.

Role of immunoglobulin subclasses and specific antibody determinations in the evaluation of recurrent infection in children

We studied humoral immune function in 267 children with recurrent respiratory infections referred to our immunology clinic to determine the most appropriate immunologic studies for evaluating recurrent infections in children. Of this highly selected population, 58% had a partial deficiency in one or more of the major immunoglobulin isotypes or IgG subclasses (defined as at least 2 SD below the normal age-adjusted mean). In none of the patients was there a total absence of an immunoglobulin isotype. The most common abnormality was partial IgA deficiency, which was found in one third of the patients. Twenty-six patients had only partial IgG subclass deficiencies, of which 20 were deficiencies of a single subclass. IgG1 was an isolated partial defect in three patients, IgG3 in five patients, and IgG2 and IgG4 were selective partial defects in six patients each. Tetanus toxoid and pneumopolysaccharide type 3 were the most immunogenic of the immunogens tested; hyporesponsiveness to pneumococcal polysaccharide types 7, 9, and 14 was common. Nineteen percent of the patients with normal immunoglobulin concentrations who were tested had lower-than-expected antibody titers; 42% of those tested with partial isotype deficiencies had deficient antibody responses. Of 25 patients with selective partial IgG subclass deficiencies or combined IgG subclass deficiencies, eight had antibody deficiencies. Our findings indicate that a high proportion of children referred to immunology clinics for recurrent infection have a demonstrable immunologic abnormality. Selective IgG subclass deficiency or a combined IgG subclass deficiency without an associated deficiency in a major immunoglobulin isotype is unusual. Identification of such patients is not predictive of the capacity to form antibodies to the antigens tested in this study and, in our opinion, adds little to the initial evaluation of immune function in such children.

IgG subclass deficiency in children with recurrent bronchitis

We studied the incidence of IgG subclass deficiency in children with recurrent bronchitis. Recurrent bronchitis was defined as three or more episodes a year during at least 2 consecutive years, of bronchopulmonary infection, productive cough with or without fever and/or diffuse râles by physical examination in the absence of asthma or atopy. Fifty three children were selected, of whom 30 (57%) were deficient in one of the IgG subclasses. None had an IgG1 deficiency. Nine (17%) were deficient in IgG2, 9 (17%) in IgG3 and 20 (38%) in IgG4. Isolated IgG subclass deficiencies were most frequently seen for IgG4 (14, 26%), less for IgG3 (6, 12%) and even less for IgG2 (4, 7%). Nine (17%) children were IgA deficient and 8 (15%) IgG deficient with a combined IgG subclass deficiency in 8 and 7 of them respectively. By subdivision into different age groups most patients were encountered in the youngest group. The mean content of IgG2, IgG3 and IgG4 in 3- to 4-year-old children with recurrent bronchitis was significantly lower than in the age matched controls. The mean value for IgG4 in the 5- to 6-year-olds was significantly lower than in the control group. This study demonstrates the correlation between recurrent bronchitis in childhood and IgG subclass deficiency. IgG subclass deficiency and recurrent bronchitis are both quite prominent phenomena in young children but rare in older children, suggesting a transient immaturity of the immune system as one of the possible pathogenetic factors. An IgA or an IgG deficiency is highly suggestive for the existence of a combined IgG subclass deficiency.

IgG subclass specific antibody response in recurrent bronchitis

The IgG subclass specific immune response against pneumococcal type 3 polysaccharide antigen before and after immunisation in healthy children and children with recurrent bronchitis was studied. Recurrent bronchitis was defined as three or more episodes a year, during at least two consecutive years, of bronchopulmonary infection, productive cough with or without fever, and/or diffuse rales by physical examination. Twenty five patients and 15 healthy children were selected. The patient group had lower concentrations of IgG1 and IgG2 specific pneumococcal antibodies compared with healthy children, regardless of whether or not the total IgG2 concentration was low. The children with recurrent bronchitis showed a greater increase in IgG1 and IgG2 antibodies after immunisation than the controls. It is concluded that children with recurrent bronchitis show a decreased humoral immune response to pneumococcal type 3 polysaccharide antigen. This finding suggests that a defect in the humoral immune response against polysaccharide antigens is an important cause of recurrent bronchitis in childhood.

IgG subclass deficiency with or without IgA deficiency

IgG subclass deficiency (IgGSD) is difficult to define since reference materials vary between laboratories and the clinically relevant cut off levels for the various subclasses are not well known. The diagnosis of IgGSD should be based on more than one determination since the levels vary, due to various factors such as infections, operations, etc. There is a relation between IgGSD and occurrence of frequent infections, but at the same time even total lack of a subclass can be seen in healthy individuals. Infections in the upper and lower respiratory tract predominate. Gm allotypes influence IgG subclass levels. Most IgGSD patients are homozygous in the Gm system. Immunocytes producing IgG3 in the nasal mucosa correlate with serum IgG3 levels, whereas rectal IgG1 producing cells relate to serum IgG1 levels. This may reflect differences in antigen and/or mitogen exposure at the two mucosal sites. IgG2SD is the predominant form of IgGSD among children, whereas after puberty IgG3SD is most common. At the same age period there is a switch in sex distribution from three boys/one girl to one male/three females. Various abnormalities in B and T lymphocyte numbers and function are often found. In a double blind crossover study of Ig prophylaxis over 2 years in 43 IgGSD adult patients a significant decrease in the number of days with infections was seen both in the whole group and among the IgG1 deficient. Days with bronchial constriction were also significantly decreased among the 22 patients who had asthma as well. Acute bronchitis became significantly less frequent in the IgG3 deficient patients during Ig prophylaxis. This was seen in those under the lower range of 0.41 g/liter of Oxelius' early normal material, although many recent reference materials suggest 0.14-0.15 g/liter of IgG3 as the cut off. In a group of 25 consecutive patients with IgGSD + IgA deficiency recurrent respiratory infections were the major problem and lung function impairment was found in 12, and bronchiectasies in 5. Still many individuals with this combined deficiency have been reported to be healthy, again illustrating our limited understanding of these conditions.

Interpretation of IgG subclass values: a comparison of two assays

Because we have noted discordant results in the measurement of IgG subclass concentrations by means of a widely available commercial radial immunodiffusion (RID) kit in comparison with an enzyme-linked immunosorbent assay (ELISA) developed at the Centers for Disease Control (CDC), we conducted in a blinded manner a comparison of the two assays, using sera from 48 healthy children. The correlation coefficients between the assays were 0.92, 0.82, 0.93, and 0.86 for the IgG1, IgG2, IgG3, and IgG4 assays, respectively. However, the RID assay assigned lower values for IgG1 and IgG4 determinations than the ELISA did. Furthermore, the "normal lower range values" provided by the RID assay were higher for each IgG subclass. When the sera from the healthy control subjects were analyzed with the RID assay, 12 (25%) of 48 subjects had values below the normal range for at least one subclass measurement. In contrast, with the CDC ELISA, all values were within the 95% confidence limits determined for the CDC ELISA. We suggest that age-specific normal limits be established with the use of sera from many healthy subjects for any assay measuring IgG subclass concentrations. As new groups of immunodeficiencies are defined and potential therapies are advocated, careful attention to assay standardization will result in a clearer delineation of these disease groups and of their response to treatment.

Selective IgG subclass deficiency: quantification and clinical relevance

Each of the four human IgG subclasses exhibits a unique profile of effector functions relevant to the clearance and elimination of infecting microorganisms. The quantitative response within each IgG subclass varies with the nature of the antigen, its route of entry and, presumably, the form in which it is presented to the immune system. This results in antibody responses to certain antigens being predominantly or exclusively of a single IgG subclass. An inability to produce antibody of the optimally protective isotype can result in a selective immunodeficiency state. This is particularly apparent for responses to certain bacterial carbohydrate antigens that are normally of IgG2 isotype. A failure to produce the appropriate specific antibody response may result in recurrent upper and/or lower respiratory tract infection. Careful patient investigation can identify such deficiencies and suggest appropriate clinical management. In this review we outline the biology and clinical relevance of the IgG subclasses and summarize current rational treatment approaches.

Immunologic and clinical status of blood donors with subnormal levels of IgG2

To determine the immunologic and clinical status of individuals from a general population with subnormal levels of IgG2, we prospectively studied 37 of 312 blood donors with low IgG2 levels identified among 8015 donors. We examined (1) G2m(23) allotypes, (2) levels of other IgG subclasses and immunoglobulin classes, (3) composition of peripheral leukocyte populations, (4) responses to two carbohydrate antigen vaccines, (5) in vitro secretion of IgG subclasses by isolated lymphocytes after mitogen stimulation, and (6) clinical histories. We found that most (90%) individuals with subnormal IgG2 levels had G2m(23)- allotypes, whereas only 30% of the unselected donors had G2m(23)-. When individuals were separated according to their G2m(23) allotype, we found that IgG2 "normal" range for individuals with G2m(23)- allotype is 35% lower than for individuals with G2m(23)+ allotype. Individuals who had G2m(23)- allotype and had IgG2 levels greater than or equal to 0.8 but less than 1.3 gm/L had no other immunologic abnormalities. In contrast, the individuals with G2m(23)+ allotype and with IgG2 levels less than 1.3 gm/L and the individuals with G2m(23)- allotype and with IgG2 levels less than 0.8 gm/L often had additional immunologic abnormalities, including IgA and/or IgG4 deficiency and decreased in vitro expression of IgG2 subclass. None of these individuals had a clinical history remarkable for recurrent infections. Thus, subnormal IgG2 levels interpreted with G2m(23) corrected normal ranges may be a marker of other immunologic abnormalities but taken alone probably have little clinical significance in a general healthy population.

Subnormal serum concentrations of IgG2 in children with frequent infections associated with varied patterns of immunologic dysfunction

To characterize more fully the immunologic basis for increased susceptibility to infection in patients with low serum concentrations of IgG2, we identified eight infection-prone children, 1 to 2 years of age, with serum IgG2 concentrations greater than 2 SD below the mean for age and followed their serologic and clinical courses for 1 to 3 years. Two of the eight children became clinically and immunologically normal and may have had transient IgG2 deficiency with an exaggerated developmental delay of this late-maturing subclass. The remaining six subjects had persistently subnormal or low-normal serum IgG2 levels and continued to experience frequent infections. All six of these children responded poorly to Haemophilus influenzae type b (Hib) polysaccharide, and four of six responded poorly to Streptococcus pneumoniae type 3 polysaccharide. Both IgG1 and IgG2-specific antibody responses to these vaccines were abnormal. Three of these six children also responded poorly to tetanus toxoid, an antigen that normally induces a predominant IgG1 response. Although five of these six children produced antibodies in response to Hib polysaccharide protein conjugate vaccine, three of four given Hib oligosaccharide CRM conjugate vaccine required booster doses to respond, a pattern of response characteristic of infants less than 6 months of age. Further, although serum concentrations of IgG1 were normal, peripheral blood mononuclear cells from four of six children tested produced extremely small amounts of IgG1 and IgG3 as well as IgG2. Finally, varied patterns of abnormalities of IgG, IgA, IgM, and IgG4 became apparent in five of the six children with persistently low serum IgG2 values. This study demonstrates that subnormal serum concentrations of IgG2 may be associated with varied patterns of immunologic dysfunction, some of which are evolving and may be responsible for increased susceptibility of these children to infection.