Serum-IgE levels in rural Namibian infants.

Serum IgE levels were examined in 237 infants ages 2 wk to 12 mo in a remote rural area of Namibia. There was a wide range of values (0.5 to 884 IU/ml). The highest value in the first month of life was 295 IU/ml. Median values for the age groups 2 wk to 3 mo, 3 to 6 mo, and 6 to 12 mo were higher than those reported from Western countries. Values in general increased with age, but only 4% of the variation is explicable on this basis. There were differences between median values for male and female infants, but they did not reach statistical significance at the 5% level. Levels between Baster and Nama infants, the main ethnic groups in the area, did not differ. The median IgE levels in breast-fed infants, although high, tended to be lower than those in weaned infants. The differences were not statistically significant (p greater than 0.05). Investigations did not suggest that parasitic infestations or atopy were of significant importance. It was not possible to identify the factor(s) responsible for the high IgE levels. They must have been operative from very early life. However, the basic immunologic mechanisms involved are presumably genetically determined and similar to those responsible for the corresponding high IgG, IgA, and IgM levels reported in infants from developing communities.