[Analysis of GM2 and anti-GM2 antibody in normal pregnancy]

Oncofetal antigen immunogenic (OFA-I), an antigen common to the fetal brain and some malignant tumors (derived from ectoderm), is immunogenic in man, and anti-OFA-I antibody appears in the sera of not only malignant patients but also pregnant women. Biochemical analysis revealed that OFA-I is ganglioside GM2 and GD2. In the present study, GM2 and anti-GM2 antibody were investigated as to the kinetics in pregnant sera and the tissue localization in placenta and decidua. The results obtained were as follows: 1. The concentration of GM2 was 76.7 pmol/ml (mean) in pregnant sera and 10.8 pmol/ml (mean) in cord sera. GM2 was not measurable in the sera of non-pregnant women. 2. GM2 was detected by thin layer chromatogram-immunostaining methods in the gangliosides extracted from decidua and term placenta. GM2 was, however, undetected from villi at an early stage. 3. In immunohistological analysis for GM2, positive findings were observed in decidua and in villous stroma of term placenta. In contrast, no distinct positive findings were observed in trophoblast at any stage. 4. Anti-GM2 antibody appeared in pregnant sera at an early stage and was detectable up to the 5th day postpartum.