Vimentin dynamics during the mitogenic stimulation of mouse splenic lymphocytes

We have used double immunofluorescence and electron microscopy to examine the distribution of tubulin and vimentin during the stimulation of mouse splenic lymphocytes by the mitogen concanavalin A. In unstimulated cells, vimentin forms a filamentous network partially coincident with the radial pattern of microtubules. In stimulated cells, the numbers of microtubules assembled from the centrosome have increased and vimentin is organized as an aggregate located near the centrosome. When these cells enter mitosis, vimentin is arranged into a filamentous cage enclosing the mitotic apparatus. During cytokinesis, the polar centrosomes are observed at a position adjacent to the midbody and vimentin is detected as an aggregate, similar to that seen prior to mitosis, close to the centrosome in each daughter cell. Using several agents, such as colchicine, colcemid, nocodazole, and taxol, which affect microtubule assembly, we have observed that the vimentin system, although closely related spatially to the microtubule complex in lymphocytes, can still reorganize independently as these cells progress through the cell cycle. Throughout mitogenic stimulation in the continued presence of taxol, microtubules are reorganized into a few thick bundles while the vimentin system undergoes a sequence of rearrangements similar to those observed during normal stimulation. These data suggest that vimentin dynamics may be important in the progression of lymphocytes through the cell cycle in response to mitogen.