IgG subclasses serum concentrations in a population of children with Down syndrome: comparative study with siblings and general population.

Serum total IgG and subclasses were determined in three different groups of children: with Down syndrome, their siblings and general pediatric population. Several cases of IgG2 and IgG4 deficiency were identified, predominantly in children with Down syndrome. The differences, considering three age groups, were statistically significant for both groups in relation to the general population group, with an increase of IgG1 and IgG3 and a decrease in serum concentrations of IgG2 and IgG4. Down syndrome children and their siblings tend o have a similar variation of the IgG4 serum concentration levels (P < 0.05). The mechanisms of this concordance are not well understood. The results point out that an adequate strategy to improve the immune status of Down syndrome children could have a positive manifestation in the immune profile of their brothers.