Direct demonstration of the presence of two immunologically distinct intermediate-sized filament systems in the same cell by double immunofluorescence microscopy: Vimentin and cytokeratin fibers in cultured epithelial cells

The epithelial derived cell lines PtK2 and HeLa were characterized by double immunofluorescence microscopy using purified antibodies against vimentin and prekeratin. The results show that both cell types express simultaneously two immunologically distinct intermediate-sized filaments. Use of colcemid-treated cells confirms that the vimentin fibers and not the keratin-related fibers are rearranged into coils around the nucleus. In some cells staining of fibrous fragments is observed, which are perhaps involved in the synthesis or breakdown of this class of filaments. The concept that growing cells derived from differentiated cell types express not only the intermediate-sized filament system typical of the differentiated cell type but in addition contain intermediate-sized filaments of the vimentin type is discussed.