Coexpression of intermediate filament polypeptides in human fetal and adult tissues

Tissues from human fetuses (12 to 14 weeks) were studied by using immunohistochemical methods, with special emphasis on coexpression of intermediate filaments. Well-characterized antibodies, monoclonal as well as polyclonal were used. Indirect immunoperoxidase staining disclosed simultaneous expression of cytokeratin and vimentin, or vimentin and desmin in several tissues, whereas some other tissues coexpressed three classes of intermediate filaments, i.e., cytokeratin, vimentin, and desmin. Coexpression of cytokeratin and vimentin was seen in immature tubules of the kidney localized in the blastema and in one case in a small area of the epithelium of the tongue. Coexpression of vimentin and desmin was found in stromal cells of the medulla of the kidney, in stromal cells of the decidua (maternal tissue) and in muscle cells in blood vessels of small intestine, kidney and decidua. Coexpression of cytokeratin, vimentin, and desmin was present in mesothelial cells of serosa, pleura and pericardium, in stroma of umbilical cord and placental villi, in muscle cells of small intestine, tongue, and heart, and in muscle cells of blood vessels of lung, heart, umbilical cord, and placental villi. Mesothelium and reactive submesothelial stroma cells also coexpressed three classes of intermediate filament polypeptides. In some cases, immunoperoxidase results were confirmed by double labeling immunofluorescence microscopy or by immunoblotting experiments. The results of this study indicate that coexpression of different types of intermediate filaments is a more general phenomenon in fetal tissues than previously realized and it also occurs in some reactive proliferative lesions in the adult.