Serum IgG and IgG Subclass Contents in Different Gm Phenotypes

Different serum IgG and IgG subclass levels were found among Gm phenotypes of a normal population. One hundred and fifty-seven Caucasian blood donors were investigated for the reciprocal Gm allotypes on IgG subclass loci namely: for IgG1, Glm(f) and Glm(a); for IgG2, G2m(n) and G2m("); and for IgG3, G3m(b) and G3m(g), and subgrouped in the seven most common Gm phenotypes. The frequencies of Gm phenotypes and haplotypes were given, including numbers of the previously little known G2m(n,") heterozygous individuals. Mean serum quantities ±SD and range of IgG, IgG1, IgG2, IgG3 and IgG4 were given for different Gm phenotypes. The IgG content was significantly lower in the Gm(f,",b/f,",b) phenotype in which the IgG2 levels were also significantly lower, compared with values of the other phenotypes. IgG3 levels were significantly lower in the Gm(a,",g/a,",g) phenotype compared with other phenotypes. These data imply the importance of Gm(f,",b/f,",b) and Gm(a,",g/a,",g) phenotypes causing lower amounts of IgG antibodies. In evaluating IgG subclass deficiency, the range for the low responding Gm(f,",b/f,",b) and Gm(a,",g/a,",g) phenotypes should be considered.