Immunoglobulin G subclasses in wheezing infants

Background: The wheezing infant is a common but difficult patient to approa ch diagnostically. The prevalence of immunoglobulin (Ig) G subclass deficie ncy in wheezing infants is still controversial. Methods: We studied the serum concentration of IgG subclasses in 38 wheezin g infants (aged 6-24 months) who had not received systemic steroids before investigation and in 30 healthy age matched controls (aged 6-24 months). Results: The prevalence of one or more IgG subclass deficiencies was 31.6% in wheezing infants and 26.7% in controls. There was no significant differe nce in prevalence of IgG subclass deficiency between patients and controls (P > 0.05). The mean concentration of IgG subclasses in patients were compa red with controls. There was no significant difference in mean serum concen tration of IgG(1), G(2) and G(3) subclasses. However, there was a trend tow ards higher concentrations of IgG(4) in wheezing infants and this differenc e for IgG(4) was significant (P < 0.01). Immunoglobulin G subclass deficien cy was found in 25 and 36.4% of wheezing infants who had experienced from t wo to four and five or more wheezing episodes in 2 years, respectively (P > 0.05). Conclusion: Our findings suggest that wheezing in infancy is not associated with IgG subclass deficiency, and in wheezing infants low IgG subclasses l evels do not increase the frequency of wheezing. However, there is a relati onship between recurrent wheezing and serum IgG(4) subclass concentration.