Serum IgG subclass levels in a group of healthy Thai children.

Gammaglobulins are the major components of the humoral immune response to foreign antigens. Yet, they may cause disease, for example, in certain malignancies or autoimmune disorders. The discovery of IgG subclasses, IgG1-IgG4, has further led to the realization that various gammaglobulin deficiencies may be ascribed to IgG subclass abnormalities. In order to establish a set of reference values in Thai children we have determined the range of total IgG and IgG subclass levels among a cohort of 195 healthy Thai children chosen semi-randomly from those at the Well Child Clinic, Chulalongkorn Hospital, who fitted certain inclusion criteria such as absence of recent infection or history of recurrent infections. The sera obtained were subjected to a laboratory test performed by means of a commercially available kit which uses the radial immunodiffusion technique for distinguishing the different IgG subclasses. The results obtained showed the total immunoglobulin increasing with age, as well as subclasses IgG1, IgG2 and IgG4, whereas subclass IgG3 remained at an almost constant level, irrespective of the age group tested.