GM allotypes and IgG subclass concentrations in blacks.

IgG subclass concentrations were measured in 352 black Americans. Sera were also typed for nine GM allotypes. Serum concentrations of IgG1, IgG3, and IgG4 varied, to different degrees, according to GM phenotypes. The concentration of IgG1 was lower in subjects with GM 1,3,17 5,6,13 compared to those who lacked this phenotype. Elevated levels of IgG3 and IgG4 were associated with GM 1,17 5,6,13 and GM 1,3,17 23 5,13, respectively. Subjects with GM 1,17 5,13,21 had lower levels of IgG3 than individuals with other phenotypes. IgG2 levels were not associated with any of the GM phenotypes. To our knowledge, this represents the first report of an association between GM allotypes and IgG subclasses in blacks.