Allotype-associated differences in concentrations of human IgG subclasses.

The concentrations of seven immunoglobulin isotypes (IgA, IgE, IgM, IgG1, IgG2, IgG3, and IgG4) were measured in the sera of 207 Finnish blood donors, and they were allotyped with anti-Gm antibodies: anti-f, anti-a, anti-x, and anti-n. The above population could be divided into 12 phenotypes, and significant differences in isotype concentrations between different phenotypes were observed. They are best explained by postulating that the following alleles of different loci are associated with a high concentration of the product of the locus: a(x)-IgG1, n-IgG2, b-IgG3, and perhaps 4b-IgG4. The following concentration differences between the low and the high homozygotes were found: IgG1, 1.2-fold; IgG2, 1.5-fold; and IgG3, 2.6-fold. No significant allotype-associated differences in the concentrations of IgA, IgM, or IgE could be detected.