Cells often use diffusible molecules to communicate with one another, but new work from Watkins and Salter shows that some cells are hard-wired for communication through structures they call nanotubules. The authors were exploring how human monocyte-derived dendritic cells respond to soluble factors released from bacteria (ECS, for E. coli supernatant). When such compounds were applied near an individual cell in culture with a micropipette, the stimulus appeared not to spread by diffusion, but rather to pass from one cell to another. High-resolution differential interfering contrast microscopy revealed tubular structures up to 100 μm in length and 20 to 200 nm in diameter connecting the cells. When cells were labeled with a calcium-sensitive dye, an increase in the concentration of free intracellular calcium caused by mechanical stimulation of one cell could be seen to pass to another through the nanotubules. Furthermore, THP-1 monocytes, which themselves don't respond to ECS, showed calcium responses within seconds of addition of ECS compounds near adjacent dendritic cells. The authors propose that immune cells may use such communication to distribute intracellular signals across large networks of interconnected cells.
S. C. Watkins, R. D. Salter, Functional connectivity between immune cells mediated by tunneling nanotubules. Immunity 23, 309-318 (2005). [PubMed]