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.