GM phenotypes influence the concentrations of the four subclasses of immunoglobulin G in normal human serum

The concentrations of the four subclasses of IgG were measured in the sera of 116 adult healthy Caucasian blood donors. Sera were also typed for nine GM determinants. All IgG subclass concentrations were significantly associated with GM phenotypes. The concentration of IgGl was lower in subjects with the GM 3 23 5,13 phenotype as compared with those who lacked this phenotype. Increased levels of IgG2 and IgG4 were associated with GM 1,2,3,17 23 5,13,21 and GM 1,3,17 23 5,13,21, respectively. IgG3 concentrations were the lowest for subjects with the GM 1,2,17 21 phenotype, intermediate for GM 1,3,17 5,13,21, and the highest in subjects with GM 3 23 5,13.