Blood-derived dendritic cells and macrophages, both antigen-presenting cells, make use of these so-called tunneling nanotubules to relay molecular messages, report Simon C. Watkins, Ph.D., and Russell D. Salter, Ph.D. Further research may show there are additional cell types with these microscopic tunnel connections. Thus far, their studies suggest the tunnels do not exist between commonly used fibroblast and tumor cell lines.
Interestingly, if not for a minor mishap while carrying out an experiment, the authors might not have discovered the existence of these physical structures and conducted the studies that revealed their role in intercellular communication.
Using a custom-built, multi-camera live cell microscopic imaging system, they report that, in a matter of seconds, dendritic cells and macrophages can send waves of calcium and other small molecules to cells hundreds of micrometers away. Each nanotubule measures between 35 and 200 nanometers across 5000 times smaller than the width of a human hair and at any given time, cells may have up to 75 of these extensions, each of varying lengths.
"Considering their scale, these nanotubules are allowing communication between fairly distant cells. If instead of a culture dish we were talking about a large metropolitan area, the distance would be about the equivalent to four or five city bloc