Immunoglobulin G subclass

Keywords: IgG subclass

Specimen:

5 mL blood in plain tube.

Method:

Immunoassay.

Reference Interval:

Refer to laboratory.

Application:

Diagnosis of IgG4 related disease of very limited use 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 deficiency is of uncertain significance.

Reference:

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