IgG subclass measurements are really only useful in the investigation of suspected immune deficiency. Levels vary with age. IgG2 (and IgG4) levels are physiologically low in infancy and may not reach adult levels until 10 to 12 years of age IgG subclass measurements may be more important in patients with IgA deficiency.IgG2 and combined IgG2 /IgG4 deficiency are of particular concern. There is little point in generally measuring subclass levels although they can be raised in certain diseases.
Raised levels are IgG4 levels tend to higher in atopic individuals and can be raised in some autoimmune diseases and in cystic fibrosis.
IgG1 can be very high in Sjögrens syndrome.
Of limited value in further investigation of IgG deficiency; recurrent bacterial infection.
Any marked deficiency in IgG subclass, particularly in children, should be investigated further by lymphocyte typing.
Serum Separator Tube (SST)
IgG2: 1.2-6.6g/ L
Assay range notes
Age specific – report form references are corrected for age. It should be noted that some children do “develop their immunoglobulin repertoire” slower than others. IgA, IgG2 and IgG4 levels often being slow to reach adult levels.