Causes of variation in serum IgE levels in normal populations.

Serum IgE was measured in 326 individuals 5 years of age and older who were members of families of both black and white populations. IgE levels were higher in blacks than in whites and much higher in children than in adults. No marked change with age was detected in children 5 to 15 years of age, but IgE levels decreased rapidly with increasing age after 15. Secretors of ABH substances had higher IgE levels than nonsecretors, but sex, blood group systems ABO, MN, and Rh had no effect on IgE levels. Levels varied widely from person to person and showed almost continuous frequency distributions. Comparisons among relatives revealed that, in the populations under study, from 40% to 50% of the total variation was accounted for by genetic variation. The basis of variation in IgE levels appears to be polygenic, that is, in addition to environmental factors many genes may contribute to the end product. Levels of IgE appeared to be independent of those of the other 4 classes of immunoglobulins.