Studies on the origin of human amniotic fluid cells by immunofluorescent staining of keratin filaments.

Cultivated cells obtained by amniocentesis for antenatal diagnosis were examined for the presence of keratin filaments by immunofluorescent staining techniques. In primary cultures, cells in fibroblast type colonies do not possess keratin filaments whereas cells in epithelial type colonies show positive staining of keratin fibres. The majority of cells in amniotic fluid type colonies also stain positively with antikeratin antibody. After the primary cells have been subcultured, most of them appear fibroblastic yet stain positively with antikeratin antibody. The patterns formed by these stained fibres resemble those seen in primary cultures of amniotic fluid type cells. These results indicate that the amniotic fluid type cells (which predominate in primary cultures) and the majority of cells in subcultures (routinely used for antenatal diagnosis of genetic metabolic disorders) are epithelial in origin.