Immunoglobulin G subclasses in wheezing infants.

Background: The wheezing infant is a common but difficult patient to approach diagnostically. The prevalence of immunoglobulin (Ig) G subclass deficiency in wheezing infants is still controversial.

Methods: We studied the serum concentration of IgG subclasses in 38 wheezing 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 difference in prevalence of IgG subclass deficiency between patients and controls (P > 0.05). The mean concentration of IgG subclasses in patients were compared with controls. There was no significant difference in mean serum concentration of IgG1, G2 and G3 subclasses. However, there was a trend towards higher concentrations of IgG4 in wheezing infants and this difference for IgG4 was significant (P < 0.01). Immunoglobulin G subclass deficiency was found in 25 and 36.4% of wheezing infants who had experienced from two 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 levels do not increase the frequency of wheezing. However, there is a relationship between recurrent wheezing and serum IgG4 subclass concentration.