IgG subclass concentrations and Gm allotypes in IgA-deficient and normal pregnant women.

IgG subclass concentrations were measured in the serum of 40 IgA-deficient (IgA concentration < 0.01 milligram) and 38 normal women in the second trimester of pregnancy. In the IgA-deficient group, 2 women were also deficient in IgG2 and IgG4, while a further 10 had very low concentrations of serum IgG4 only. These low IgG4 values were unrelated to the presence of anti-IgA antibodies. The incidence of low IgG4 values was significantly greater (p < 0.01) than in the control group where only 1 woman had low IgG4 and none had low IgG2. Mean values for total IgG, IgG1 and IgG3 were very significantly higher (p < 0.001) in the IgA-deficient group than in the control group. These differences were unrelated to Gm phenotype.