Serum levels of IgG subclasses in relation to IgE and atopic disease in early infancy.

The levels of IgG1, IgG2, IgG3, and IgG4 were analysed by ELISA in cord serum and in serum samples collected at 6 and 18 months of age from infants whose mothers were atopic. None of the four IgG subclasses was significantly influenced on any sampling occasion by infant atopy, gender, month of birth, maternal IgE or maternal diet during pregnancy and early lactation. However, at 18 months of age, significantly higher levels of IgG1 (P less than 0.05) and of IgG4 (P less than 0.01) were found in infants with an elevated IgE (greater than or equal to 8.0 kU/l) than in those with a lower level. A weak positive correlation (rs = 0.26; P = 0.05) between IgE and IgG4 was also observed. Despite the fact that the serum levels of IgG4 at 18 months were significantly higher (P less than 0.01) among infants with positive IgE-RAST (greater than or equal to 0.15 PRU/ml) to ovomucoid or beta-lactoglobulin, our data suggest that the the concentration of IgG4 relates more to the level of IgE than to the clinical symptoms of atopy. Determination of IgG subclasses seems to be of limited value for prediciting atopy during early infancy.