Normal IgG Subclass Levels Research Articles

Étude de la fonctionnalité des sous classes d'IgG

Children who have recurrent infections require laboratory investigation for eventual immunodeficiency. We measured specific IgG antibodies against tetanus toxoid, diphteria toxoid, pneumococcal capsular polysaccharide and Haemophilus influenzae b in serum of 70 children without pulmonary symptoms. We compared to the study of humoral immune function in 128 children with obstructive bronchopneumopathies.We observed that functional antibody deficiency may be present despite normal IgG subclass levels and conversely deficiency levels of a single subclass of IgG may be found in individuals who have effective specific antibody production and are clinically normal. Measurement of specific antibody response to bacterial antigens and the identification of children with selective antibody deficiency are important for diagnostic and therapeutic management.

Post-immunization pneumococcal antibody titers and IgG subclasses.

IgG antibodies against pneumococcal polysaccharides are found predominantly within IgG subclass 2. We wished to evaluate retrospectively IgG subclasses and post-immunization pneumococcal antibody titers in children with recurrent respiratory infections. We examined total immunoglobulin levels and IgG subclasses, as well as pneumococcal antibody titers against serotypes 3, 7F, 9N, and 14 present 4-6 weeks after pneumococcal immunization in 56 children 2-18 years old. Titers > 200 ng Ab N/ml to any of the 4 serotypes tested were arbitrarily considered protective. Four patients did not have protective antibody levels against any of the 4 serotypes tested following vaccination. Of those, 3 had normal IgG subclass levels and 1 had an IgG2 subclass deficiency. Of 3 additional patients with IgG2 deficiency, 2 had protective antibody levels to only 1 serotype and 1 had protective antibody levels to 2 serotypes. Furthermore, in 2 patients with undetectable IgG2 at the time of immunization, the response was only transient. We conclude that patients with IgG2 deficiency may not develop protective antibody levels to all pneumococcal serotypes and that some may have deficient memory for IgG anti-pneumococcal polysaccharide antibodies.

Transient IgG subclass deficiencies in newly diagnosed diabetic children.

In 27 children (15 males and 12 females) with insulin-dependent diabetes mellitus (IDDM), aged 1.2-13.5 years (mean 9.9 +/- 3.6 years) we investigated immunoglobulins (IgG, IgA, IgM), IgG subclass levels and islet-cell antibodies (ICA) at diagnosis and at 6 and 12 months after disease onset. At diagnosis, IgG levels were lower than -2SD in 7 patients (26%), IgA in 1 (3.7%), IgM in 1 (3.7%). IgG subclass levels were below the 3rd percentile in 13 patients (48.1%); in particular IgG1 in 7 (26%), IgG2 in 3 (11.1%), IgG3 in 2 and IgG4 undetectable in 1 case. In 3 out of the 13 patients combined IgG1-IgG3, IgG1-IgG2 and IgG1-IgG4-IgA deficiencies were observed. ICA were greater than 20 Juvenile Diabetes Foundation units in 17/27 patients. The HLA-DR2 frequency was higher in patients with IgG subclass deficiency than in patients with normal IgG subclass levels. During follow up, IgG levels normalized in 6 patients while IgA and IgM did not change. IgG1 normalized in 5 out of the 7 patients, IgG2 in all patients while IgG3 and IgG4 did not change. One year later ICA were still present in 8/27 patients. The hypogammaglobulinaemia and IgG subclass deficiencies observed in our patients could have either a genetic or an acquired basis.

Impaired lung function in patients with IgA deficiency and low levels of IgG2 or IgG3.

We examined the relation between serum levels of IgG subclasses and lung function, as determined by spirometry, lung volumes, the single-breath nitrogen test, and static recoil pressures, in 29 patients with IgA deficiency and repeated upper or lower respiratory tract infections. Four of the patients had decreased levels of IgG2, and two had decreased levels of IgG3. Two or more lung-function values were abnormal in each of these six patients and also in three others with normal levels of IgG subclasses. Low levels of IgG2 and IgG3 were significantly related to abnormal lung function (P less than 0.01). The 20 patients with normal lung function all had IgG-subclass levels above the lower range. There may be a causal relation between low levels of IgG subclasses and deterioration in lung function, suggesting that patients with combined IgA and IgG-subclass deficiencies may benefit from immunoglobulin prophylaxis.