Sexual dimorphism of heritability of immunoglobulin levels.

Heritability of IgA, IgG and IgM levels was studied in 85 MZ and DZ twin pairs of both sexes. Immunoglobulin concentrations were determined by single radial diffusion. Significantly higher geometric mean of IgM level in females than males was demonstrated. Heritability coefficients h2, F and VG/VE were higher in male than female twins. This suggests that genetic factors play a more important role in males as compared with females in regulating the three immunoglobulin levels. Quantitative comparison of genetic variances of both sexes indicated slightly greater genetic influence in the case of IgA in females. Environmental variances of IgA and IgM levels were also higher in females than males.