A reference interval for serum IgG subclasses in Chinese children

Disturbances in the IgG Antibody Profile in HIV-Exposed Uninfected Infants Associated with Maternal Factors

Over the last 20 years, the incidence of vertical HIV transmission has decreased from 25%-42% to less than 1%. Although there are no signs of infection, the health of HIV-exposed uninfected (HEU) infants is notoriously affected during the first months of life, with opportunistic infections being the most common disease. Some studies have reported effects on the vertical transfer of antibodies, but little is known about the subclass distribution of these antibodies. We proposed to evaluate the total IgG concentration and its subclasses in HIV+ mothers and HEU pairs and to determine which maternal factors condition their levels. In this study, plasma from 69 HEU newborns, their mothers, and 71 control pairs was quantified via immunoassays for each IgG isotype. Furthermore, we followed the antibody profile of HEUs throughout the first year of life. We showed that mothers present an antibody profile characterized by high concentrations of IgG1 and IgG3 but reduced IgG2, and HEU infants are born with an IgG subclass profile similar to that of their maternal pair. Interestingly, this passively transferred profile could remain influenced even during their own antibody production in HEU infants, depending on maternal conditions such as CD4+ T-cell counts and maternal antiretroviral treatment. Our findings indicate that HEU infants exhibit an altered IgG subclass profile influenced by maternal factors, potentially contributing to their increased susceptibility to infections.

Sudden death of a child associated with invasive non-typeable Haemophilus influenzae infection with underlying IgG2 subclass deficiency

Haemophilus influenzae can be divided into typeable and non-typeable strains. Although non-typeable Haemophilus influenzae (NTHi) is less likely to be a fatal bacterium, invasive NTHi infection has been reported to increase worldwide. This study presents a case of sudden death of a child with invasive NTHi infection and underlying immunoglobulin G2 (IgG₂) deficiency. A two years seven months male child with a high fever was found unresponsive in bed, lying face down on a soft pillow. Later, the hospital declared the subject dead. An autopsy revealed that the only noteworthy finding was tissue congestion. The histopathological findings disclosed neutrophils within blood vessels of major organs. Meanwhile, the formation of the micro abscess was not visible, which indicated bacteremia. The bacterial blood culture was positive for Haemophilus Influenzae. Polymerase chain reaction assay revealed the absence of an entire capsule locus. The transmission electron microscopy showed that the colonies did not have polysaccharide capsules. Based on the above findings, the strain was identified as NTHi. Furthermore, the value of serum IgG₂ was deficient, indicating the presence of IgG₂ subclass deficiency. The subject eventually died from asphyxia by smothering due to a comorbid condition with a high fever brought on by NTHi-induced bacteremia and lying face down. IgG₂ subclass deficiency contributed to the development of invasive NTHi infection. The invasive NTHi infection might present a risk of sudden death, particularly for immunocompromised children. As forensic pathologists and pediatricians may encounter such a problematic clinical condition, they should be aware of this.

Low immunoglobulin G4 subclass level is associated with recurrent wheezing in young children

Background

The most important infectious trigger of asthma is the virus and patients with immunoglobulin deficiencies are prone to recurrent respiratory infections.

Objective

We investigated the relationship between immunoglobulin G subclass and recurrent respiratory symptom exacerbation and explored possible therapeutic effects of intravenous immunoglobulin administration.

Methods

Twenty-eight infants less than 24 months old with 2 or more recurrent wheezing episodes (infantile wheezer group) and 29 asthmatic children aged 24 months to 15 years (bronchial asthma [B-asthma] group) visited our hospital from October 2010 to January 2018. Serum immunoglobulin G, A, M, E, G1, G2, G3, and G4 were measured in each group and compared. In both groups, serum immunoglobulin and symptoms were compared before and after intravenous immunoglobulin administration.

Results

The 2 study groups exhibited several statistically significant differences when comparing respiratory virus infection rate (p < 0.001), coinfection rate (p < 0.0001), most commonly found viral infection (human bocavirus vs. human rhinovirus), and immunoglobulin A (p < 0.001), E (p = 0.008), G2 (p < 0.001), and G4 (p = 0.011) levels. In the infantile wheezer group, there was an inverse correlation between immunoglobulin G4 levels and wheezing numbers (R = -0.5538, P = 0.0022). Both groups showed significant changes in immunoglobulin levels and respiratory symptom exacerbations (recurrent wheezing, shortness of breath, chest tightness, cough, and fever) over 1 year after intravenous immunoglobulin administration.

Conclusion

There was an association between recurrent wheezing and specific immunoglobulin G deficiencies. We suggest that intravenous immunoglobulin therapy significantly elevates specific immunoglobulin G levels though it lasts only for short term and might be associated with decreased respiratory symptoms. Therefore, low IgG4 levels among infants with recurrent wheezing may be indicative for intravenous immunoglobulin therapy.

Immunological Role of IgG Subclasses

The loss of tolerance to self-antigens is the unequivocal "red line" of autoimmunity: both development of autoreactive T and B cells and production of polyclonal autoantibodies represent seminal keys to the pathogenesis of protean autoimmune diseases. Most of these autoantibodies are immunoglobulins G (IgG), functionally distinguished in four subclasses named IgG1, IgG2, IgG3, and IgG4, due to structural differences in the hinge and heavy chain constant regions. Different studies analyzed serum levels of IgG subclasses in the course of different disorders, showing that they might have a pathogenic role by regulating interactions among immunoglobulins, Fc-gamma receptors, and complement. To date, the mechanisms promoting different IgG subclasses distribution during the natural history of most autoimmune diseases remain somewhat unclear. Evidence from the medical literature shows that the serum IgG profile is peculiar for many autoimmune diseases, suggesting that different subclasses could be specific for the underlying driving autoantigens. A better knowledge of IgG subsets may probably help to elucidate their pathological task, but also to define their relevance for diagnostic purposes, patients' personalized management, and prognosis assessment.

Dynamics of immunoglobulin G subclasses during the first two years of life in Malawian infants born to HIV-positive mothers

Background

Maternal antibodies are key components of the protective responses of infants who are unable to produce their own IgG until 6 months of life. There is evidence that HIV-exposed uninfected children (HEU) have IgG levels abnormalities, that can be partially responsible for the higher vulnerability to infections in the first 2 years of the life of this population.

This retrospective study aimed to characterize the dynamics in plasma levels of total IgG and their isotypes during the first 2 years of life in HEU infants exclusively breastfed through 6 months of age.

Methods

Total IgG, IgG1, IgG2, IgG3 and IgG4 isotypes, and IgM and IgA plasma concentrations were determined by nephelometric methods in 30 Malawian infants born to HIV-positive women at month 1, 6 and 24 of life.

Results

At 1-month infants had a median concentration of total IgG of 8.48 g/l, (IQR 7.57–9.15), with an overrepresentation of the IgG1 isotype (89.0% of total) and low levels of IgG2 (0.52 g/l, IQR, 0.46–0.65). Total IgG and IgG1 concentrations were lower at 6 months (− 2.1 and − 1.12 g/dl, respectively) reflecting disappearance of maternal antibodies, but at 24 months their levels were higher with respect to the reported reference values for age-matched pairs. Abnormal isotype distribution was still present at 24 months with IgG2 remaining strongly underrepresented (0.87 g/l, 7.5% of total IgG).

Conclusion

HIV exposure during pregnancy and breastfeeding seems to influence the IgG maturation and isotype distribution that persist in 2-year old infants.