Functional changes of intermediate filaments in fibroblastic cells revealed by a monoclonal antibody

We describe reversible changes of intermediate filaments of fibroblastic cells associated with changes in the functional state of the cells. The changes are revealed by comparing the immunofluorescence patterns given by a monoclonal antibody and a polyclonal serum, both recognizing vimentin. The state of the filaments depends on culture density; this effect cannot be attributed to the nutritional state of the cells, their growth rate, or substances released into the medium. It seems to depend mainly on the aggregation of filaments during strong cell movements. The possible significance of these findings for the functional role of intermediate filaments is discussed.