rev:February 3, 1997

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3     IgG subclasses in healthy children and adults.

3.1     Reference values of IgG subclass levels


Children (52,56,59)

The levels of total IgG and each of its four subclasses follow a typical pattern during childhood (table lll). The IgG present at birth is mainly of maternal origin, because all IgG subclasses are capable of placental transfer. After the first 6 months of life, during which IgG levels decrease, the individual's own IgG production sets in, eventually reaching adult levels. Each IgG subclass has an individual pattern of development, IgG1 and IgG3 attaining adult levels at an earlier age than IgG2 and IgG4 (table lll). Thus, when analyzing levels of IgG and its subclasses in pediatric patients, values should be compared with reference values from the same age group.


Adults  (52,57,60)

There are numerous publications on IgG subclass levels in different populations. The levels of IgG subclasses are not normally distributed. Therefore the normal (reference) ranges of the IgG subclasses should be chosen between the 2,5 and 97,5 percentile ranges (58). IgG subclass levels are associated with certain Gm allotypes: individuals homozygous for the G3m(b) allele have higher levels of IgG3 than homozygous G3m(g) individuals. Similarly, IgG2 subclass levels are slightly higher in individuals carrying the G2m(n) allotype compared to G2m(n)-negative individuals.The reference ranges of IgG subclass level in Caucasians are shown in table lll (59,60).


TABLE III: Reference ranges (g/l) of IgG subclasses in healthy Caucasian children and adults:
IgG1 IgG2 IgG3 IgG4
age in months
0-1 2.4-10.6 0.87-4.1 0.14-0.55 0.04-0.56
1-4 1.8-6.7 0.38-2.1 0.14-0.70 <0.03-0.36
4-6 1.8-7.0 0.34-2.1 0.15-0.8 <0.03-0.23
6-12 2.0-7.7 0.34-2.3 0.15-0.97 <0.03-0.43
age in years
1-1.5 2.5-8.2 0.38-2.4 0.15-1.07 <0.03-0.62
1.5-2 2.9-8.5 0.45-2.6 0.15-1.13 <0.03-0.79
2-3 3.2-9.0 0.52-2.8 0.14-1.20 <0.03-1.06
3-4 3.5-9.4 0.63-3.0 0.13-1.26 <0.03-1.27
4-6 3.7-10.0 0.72-3.4 0.13-1.33 <0.03-1.58
6-9 4.0-10.8 0.85-4.1 0.13-1.42 <0.03-1.89
9-12 4.0-11.5 0.98-4.8 0.15-1.49 0.03-2.10
12-18 3.7-12.8 1.06-6.1 0.18-1.63 0.04-2.30
ADULTS 4.9-11.4 1.50-6.4 0.20-1.10 0.08-1.40



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