Rapid identification of glial cells in human amniotic fluid with indirect immunofluorescence

Direct preparations were made from human amniotic fluid and from suspensions of cultured amniotic fluid cells by cytocentrifugation. Specific cell types were identified by indirect immunofluorescence staining using antibodies against different types of intermediate filament proteins. In cases of anencephaly, spina bifida and Meckel's syndrome, specific staining for glial fibrillary acidic protein (GFAP) showed a fine fibrillar fluorescence in many cells, indicating their glial origin. Blood cells were abundant in the amniotic fluid preparations, and the cell types of normal amniotic fluid were also present but with the fibroblastoid cells as the dominating cell type. In normal amniotic fluid, the main cell types were terminally differentiated keratinocytes, negative for both keratin and vimentin, keratin-positive epithelial cells and vimentin-positive fibroblastoid cells. In addition, blood cells, including macrophages, were occasionally seen. GFAP-specific staining of cytocentrifuged amniotic fluid samples appears to be a rapid and reliable way of revealing glial cells in fresh (uncultured) amniotic fluid and could thus serve as an aid in the prenatal diagnosis of neural tube defects.