The study by Franke et al. (1978) investigates the immunofluorescence properties of intermediate-sized filaments in mouse 3T3 cells, focusing on a major protein identified as vimentin. Vimentin, with a molecular weight of 57,000, is distinguished from prekeratin, another intermediate filament protein. Antibodies against vimentin and prekeratin were used to examine various cultured cells and frozen tissue sections. The results show that vimentin is predominantly found in non-muscle cells of mesenchymal origin, including transformed cells, and is not detected in muscle or brain nerve tissue. In contrast, prekeratin is prevalent in epithelial cells, including epithelial-derived tumor cells, and is not decorated by vimentin antibodies. The study also notes that perinuclear aggregates of intermediate filaments, induced by Colcemid treatment, are strongly decorated with vimentin antibodies but not with prekeratin antibodies. These findings highlight the distinct immunological properties of vimentin and prekeratin, suggesting that they represent different systems of intermediate filaments.The study by Franke et al. (1978) investigates the immunofluorescence properties of intermediate-sized filaments in mouse 3T3 cells, focusing on a major protein identified as vimentin. Vimentin, with a molecular weight of 57,000, is distinguished from prekeratin, another intermediate filament protein. Antibodies against vimentin and prekeratin were used to examine various cultured cells and frozen tissue sections. The results show that vimentin is predominantly found in non-muscle cells of mesenchymal origin, including transformed cells, and is not detected in muscle or brain nerve tissue. In contrast, prekeratin is prevalent in epithelial cells, including epithelial-derived tumor cells, and is not decorated by vimentin antibodies. The study also notes that perinuclear aggregates of intermediate filaments, induced by Colcemid treatment, are strongly decorated with vimentin antibodies but not with prekeratin antibodies. These findings highlight the distinct immunological properties of vimentin and prekeratin, suggesting that they represent different systems of intermediate filaments.