Serum immunoglobulin G subclasses in healthy infants and children in Greece.

Serum concentrations of immunoglobulin IgG1, IgG2, IgG3 and IgG4 were determined by radial immunodiffusion in a sample of 414 healthy Greek children, who were admitted to the major Teaching Hospital for Children in Athens for minor surgical operations. Statistical analysis was performed by multiple regression after logarithmic transformation of the immunoglobulin values. There was a statistically significant increase of IgG3 with age, whereas IgG1, IgG2 and IgG4 levels reached a turning point at the age of five years. Older than 5 years male children were found to have marginally higher IgG4 levels than females. Low socioeconomic class was positively and significantly associated (9% increase) with IgG1 levels only among the older age group. History of frequent infections was associated with a 16% increase of IgG1 levels in the younger (less than 5 years) (p = 0.01) and with a 47% increase of IgG4 among the older age group (p = 0.03). Atopic history was associated with a 16% increase of IgG1 in the younger (p = 0.02). The findings of the present study provide an insight on the determinants and the clinical significance of IgG subclass levels among children.