[Immunohistochemical localization of pregnancy-specific beta 1-globulin in placentas at various ages].

In the study reported here the dispersion of pregnancy-specific beta 1-globulin (SP1) in placentas from the 6th to the 40th week of pregnancy was determined by means of the peroxidase-anti-peroxidase method; cytophotometric quantification of the stain reaction was also carried out. SP1 was only identified in syncytiotrophoblasts. Cytotrophoblasts, villous stroma and vascular endothelia were free of SP1. Within the syncytiotrophoblast SP1 was found in particularly large quantities in proliferation buds. Weaker reactions were obtained in the following order for: nucleated villous epithelium, non-nucleated epithelial squama, including the syncytiocapillary membranes, epithelial nodules with nuclear pyknosis and regressively changed villous epithelium associated with stromal fibrosis. Spectrophotometry of the extinction at the wave-length of the DAB-peroxidase product revealed, in relation to the age of the placenta, a relatively uniform intensity of reaction during the entire duration of pregnancy, with only a moderate rise up to the 24th week and a slight decrease until term.