This study aimed to investigate the prevalence of IgG subclass deficie
ncy in wheezy children aged <3 y. Serum levels of IgA, IgE and IgG sub
classes were measured in 310 children with recurrent wheezing and in 1
00 healthy controls. IgG3 levels were below the normal lower limit in
123 (39.6%) patients. This finding may reflect delayed maturation of t
he immune system, predisposing young children <3 y of age to wheezing.