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IgG4 deficiency in IgA-deficient patients.
1University of Adelaide, Department of Pediatrics, South Australia.
The Pediatric Infectious Disease Journal
|October 1, 1989
Summary
Immunoglobulin G4 (IgG4) deficiency is common in patients with Immunoglobulin A (IgA) deficiency and recurrent infections. This previously unrecognized deficiency may contribute to increased susceptibility to infections.
Area of Science:
- Immunology
- Clinical Medicine
Background:
- Immunoglobulin A (IgA) deficiency is associated with increased infection risk.
- Previous studies on IgG subclass deficiencies in IgA-deficient individuals were limited by assay sensitivity, hindering accurate IgG4 deficiency assessment.
Purpose of the Study:
- To investigate the incidence of IgG subclass deficiencies, particularly IgG4, in IgA-deficient patients with recurrent respiratory infections.
- To establish age-specific normal ranges for IgG subclasses using a newly developed enzyme-linked immunosorbent assay (ELISA).
Main Methods:
- Developed a sensitive ELISA for quantifying all IgG subclasses.
- Established age-normal ranges for IgG subclasses in healthy individuals.
- Measured IgG subclass concentrations in 73 IgA-deficient patients, primarily children with recurrent respiratory infections.
Main Results:
- IgG4 deficiency was the most prevalent, found in 26% of IgA-deficient patients.
- IgG1, IgG2, and IgG3 deficiencies were observed in 10%, 12%, and 8% of patients, respectively.
- Combined deficiencies, such as IgA-IgG4 deficiency (16%), were also noted.
Conclusions:
- IgG4 deficiency is a significant, often overlooked factor contributing to infection proneness in IgA-deficient individuals.
- This deficiency may play a role even when other IgG subclass deficiencies, like IgG2, are absent.