Serum immunoglobulins in healthy children and adults. Levels of the five classes, expressed in international units per millilitre.

Serum levels of IgM, IgG, IgA, IgD, and IgE were determined in serum samples of 270 healthy Dutch children (aged 4-13 years) and of 30 healthy Dutch adults, the amounts being expressed in International Units per millilitre. Special attention is given to the IgD and IgE results, since the IgM, IgG, and IgA levels in mg per 100 ml of these sera and their implications have already been reported. In the children's sera the occurrence of relatively high IgD and IgE levels was frequently observed, whereas the adult group did not show excessive variation in this respect. The mean IgD levels found for adult males and females are 21 I.U./ml and 24 I.U./ml, respectively; the mean IgE levels for the same groups are 68 I.U./ml and 88 I.U./ml, respectively. The mean IgD and IgE levels in the children of each year group were usually higher than those of each of the juvenile groups and the mean level of the adult group was not statistically significant. A statistically significant influence of sex and season on the IgD and IgE levels could not be demonstrated in this material either. Three of the 270 children's sera showed an exceptionally low IgA content. In two of these cases the serum was sampled and studied a second time after an interval of four years, when the IgA deficiency proved to be still present. The IgE levels in the sera of these healthy IgA-deficient children were normal, whereas the presence of IgD could not be demonstrated.

Quantification of IgG subclasses in sera of normal adults and healthy children between 4 and 12 years of age.

The concentration of the four subclasses of IgG was determined in sera of normal adults and healthy children between 4 and 12 years of age, using the radial immunodiffusion technique. A relation between the concentration of IgG subclasses and Gm type was studied in adults. No influence of Gm type on IgG1 concentration could be shown, except that the group of Gm(fb) individuals had a higher level than the others. The mean concentration of IgG2 was higher in sera positive for Gm(n) than in those lacking this genetic marker. High IgG3 concentrations corresponded to the presence of Gm(b). No clearcut evidence was obtained for a relation between IgG4 concentration and Gm factors, although in general Gm(n) positive individuals had higher and Gm (zag) positive individuals lower concentrations of this subclass in their serum. Quantification of IgG subclasses in sera from healthy children of different ages revealed that the amount of IgG2 rises slowly with age, having not yet reached the adult level at the age of 12 years. This also holds for IgG4, although in a lesser degree. No significant differences from the adult level were found for the concentrations of IgG1 and IgG3.