Immunoglobulin G subclasses

Last updated: Saturday, 30, June, 2007
Item Process
Specimen

5 mL blood in plain tube.

Method

Immunoassay.

Reference Interval

Refer to laboratory.

Application

Limited role in assessment of antibody-mediated immune function in patients with recurrent, severe or chronic infections, especially sinusitis and respiratory infections.

IgG subclass deficiency has been found in association with recurrent bacterial infection. However, IgG subclass deficiency is frequently not accompanied by increase in infection.

Interpretation

IgG1 accounts for 70% of serum IgG and selective deficiency is very rare.

IgG2, or combined IgG2-IgG4, deficiency is the most frequent abnormality. It has been implicated in the susceptibility of some patients, with normal total immunoglobulin levels, to infections with H. influenzae and S. pneumoniae.

In patients with chronic respiratory infection, IgG2 deficiency may be associated with IgA deficiency.

Low IgG3 levels have been reported in some rare primary immunodeficiencies (eg Wiskott-Aldrich syndrome) and in juvenile diabetes mellitus.

Isolated IgG4 defciency is of uncertain significance.

Reference

Maguire G. Ann Clin Biochem 2002; 39:4: 374-377.