The concentrations of IgG1, IgG2, IgG3 and IgG4 were determined by electroimmunoassay in 10 pairs of maternal and cord sera and in sera of 162 healthy children, aged 6 weeks to 15 years. Specific rabbit antisera against the IgG subclasses were used. The content of the normal serum pool WHO 67/97 was used as reference. The mean value, standard deviation and normal range of each IgG subclass were calculated for each age group and compared with the adult values. All IgG subclasses were present in cord serum except for IgG4 in those cases where also the maternal serum lacked demonstrable IgG4. The IgG subclasses followed the pattern of total IgG with a fall during the first 3--6 months and a subsequent gradual rise with age. The IgG1 and IgG3 levels rose faster with age than IgG2 and IgG4. Adult levels were not reached before puberty. No IgG4 was detectable in 12--21% of the children above 7 years of age.

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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, G1m(f) and G1m(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.

Oxelius V-A, Aurivillius M, Carlsson A-M, Musil K. Serun Gm Allotype Development During Childhood. Scand J Immunol 1999;50:440±446 Gm allotypes are genetic variants of the immunoglobulin heavy G chains (IGHG) of IgG molecules, coded from chromosome 14q32, characterized by differences in amino acid epitopes of the constant heavy G chains and inherited in the Mendelian manner. Gm allotypes have in¯uence on IgG subclass levels, and serum Gm allotype levels have been given for different Gm genotypes in adults. Four hundred and thirty healthy children, aged 1±15 years, were examined for serum Gm allotypes and IgG subclasses from the six most common Gm genotypes and different age groups were measured using competitive enzyme-linked immunosorbant assay and radial immunodiffusion methods. Quantities (in g/l) of G1m(a) and G1m(f) of IgG1, G2m(n) and G2m(± n) of IgG2 and G3m(g), and G3m(b) of IgG3 are given. Different maturation rates of the alternative Gm allotypes within IgG1, IgG2 and IgG3 were shown. G2m(n) development was strikingly retarded compared with G2m(±n) from the g2 locus. This was found comparing IgG2 levels from homozygous G2m(±n±n) and G2m(nn) individuals, but was also seen in heterozygous G2m(n±n) genotypes. From the g1 locus G1m(f) levels dominated signi®cantly, but inconstantly, over G1m(a) levels in heterozygous G1m(af) individuals. In homozygous G1m genotypes, G1m(aa) compared with G1m(ff) of the same age, one or the other dominated, sometimes signi®cantly. Serum levels of G3m(b) from the g3 locus of homozygous G3m(bb) individuals were increased signi®cantly compared with G3m(g) levels of homozygous G3m(gg) individuals, in ages over 3 years. However, in heterozygous G3m(gb) individuals G3m(b) dominance was not evident. There is a relatively rapid development of G1m(f) molecules and a retarded development of G2m(n) in the Gm(f;n;b) haplotype. In comparison, G1m(a) is retarded and G2m(±n) is enhanced in the Gm(a;±n;g) haplotype. The retarded serum G2m(n) development is comparable with serum IgA development during childhood. Different maturation rates of Gm allotypes within the same IgG subclass provide further explanation for the variation of the antibody response during childhood. Quantitative Gm allotype determinations give information of the activity from IGHG genes. The genetic variation constitutes an additional basis for evaluation of IgG antibodies in different diseases in childhood.