Serum levels of IgA1 and IgA2 in children and in patients with IgA deficiency

Abstract Serum levels of IgA 1 and IgA 2 were measured by solid phase radioimmunoassay in samples from 110 children between 3 months and 10 years of age. Both IgA 1 and IgA 2 were detectable in all samples, and both IgA 1 and IgA 2 increased with increasing age. The percent of total serum IgA that was IgA 2 did not change with age and was the same in samples from children (15.05 ± 10.2%) as in samples from adults (15.86 ± 7.98%). The proportion of serum IgA that was IgA 2 was much less variable within sibships than within the group at large ( P 1 or IgA 2 was highly variable. IgA 2 constituted more than 50% of the IgA in 5 patients and less than 7% of the IgA in an additional 5 patients. These findings suggest that regulation of serum concentrations of IgA 1 and IgA 2 is complex and influenced by genetic factors and probably other unidentified factors.