Immunohistochemical location of HPL, SP1 and β-HCG in normal placentas of varying gestational age

Summary

Sixty-four placentas at various gestational ages were examined by immunohistochemical stains for HPL, SP1 and β-HCG according to a modified PAP method (Sternberger 1970). Syncytiotrophoblast cell layer was identified as the main site of synthesis. Extravillous immunohistochemical reactions for HPL and SP1 (but not for β-HCG) were found in X-cells of the basal plate and in the intervillous trophoblast islands. These cell types would thus seem to be derived from trophoblast. Hofbauer-cells of villous connective tissue stained specifically for β-HCG apparently because of HCG phagocytosis. The intensity of staining for HPL, SP1 and β-HCG was evaluated semiquantitatively in the syncytiotrophoblast cell layer at various gestational weeks. The maximum of staining for β-HCG was found in the uniform syncytiotrophoblast layer of immature intermediate villi in early pregnancy (7–14 weeks), HPL and SP1 had their peak of staining reaction at 32–36 weeks of gestation. Increasing maturation results in a subspecialisation of the villous surface: epithelial plates (allowing feto maternal exchange) and nucleated portions of syncytiotrophoblast (which are the main site of hormone production and endocrine activity).