Genetic and environmental influences on serum levels of immunoglobulins and complement components in monozygotic and dizygotic twins

The influence of hereditary and environmental factors in the regulation of the serum levels of IgM, IgG and IgA and of the complement components C3, C4 and factor B has been studied. For this purpose, sera from 9 monozygotic twin pairs, from 10 dizygotic twin pairs and from two control groups were analyzed. The first control group consisted of three healthy donors analyzed once a week for three weeks, as a genetic identity experimental control, while the second one was constituted by nine subjects randomly selected as a genetic heterogeneity control. The results indicate that the serum proteins with immunological functions can be subdivided into three groups. The first, represented by IgM and IgG, appears to be under strict genetic control; the second, represented by IgA and C3, appears to be influenced either by genetic or environmental factors; the third one, including C4 and factor B, is strongly influenced by environmental factors.